the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 01 Jul 2025
Active Piedmont Zone Deformation, a manifestation of activity on the ‘Master Ray Fault’; insight into the seismic hazard analysis of the Tehran metropolitan area
Abstract. The piedmont zone in the frontal active regions of the orogenic belts exhibits various deformation patterns, which helps unravel the seismic sources for cities that flourish in such tectonic settings. A detailed analysis of the active folding, faulting, and related morphological features of the Quaternary alluvial units disclose prominent thrust faults in the Tehran piedmont zone. These faults are kinematically related and play a vital role in a better understanding of the seismic hazard of the Tehran metropolitan area. The five south-dipping thrust faults, the related hanging-wall folding and subsidiary faulting accommodate a considerable amount of north-south shortening during Quaternary. The shortening is observed in the alluviums and the underlying Eocene volcanic bedrock. Interestingly, in western Tehran, the Chitgar area discloses a type locality for active fault-bend folding, backthrusting, oblique-slip normal faulting and fault inversion in the piedmont zone. Our optically stimulated luminescence dating on the Late Pleistocene alluviums in the Chitgar area constrains the slip rate of the primary and secondary faults. According to our analyses, we introduce the ‘Master Ray Fault’ as a crucial seismogenic fault of the Tehran region, manifested as south-dipping thrust faults in the piedmont zone. We estimate the minimum slip rate on the Master Ray Fault to be ca. 0.50 mm a-1. Our study offers a crucial methodological framework for improving the existing understanding on Quaternary thrust fault kinematics and associated morphological features, aiding in the unveiling of potential seismic sources in metropolitan areas located in piedmont zones adjacent to active orogenic belts.
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RC1: 'Comment on egusphere-2025-500', Anonymous Referee #1, 12 Aug 2025
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AC1: 'Reply on RC1', Mohammad R. Ghassemi, 22 Sep 2025
Reviewer #1
This submitted manuscript proposes a new regional seismotectonic model for the region near the capital city of Tehran, Iran, based on field surveys, remote sensing interpretation, and a catalog of instrumentally recorded earthquakes. Based on observed variations in the strike of some thrust faults, the paper concludes that the "Master Ray Fault" can explain the seismogenic tectonic setting of the Tehran region's magnitude > 7 earthquakes and that tectonic explanations can also explain several historical strong earthquakes. Discussing this regional tectonic model is crucial for understanding the patterns of historical strong earthquakes and the potential for future strong earthquake hazards. While the paper has made some progress, several scientific issues remain that require further discussion and refinement:
Response: We greatly appreciate the thoughtful comments provided by Reviewer RC1. Our replies are presented after each numbered comment.
- The collision of the Arabian and Eurasian plates controls the regional tectonic model for northern Iran. The surface deformation generated by the south-to-north thrust in this region is the subject of the paper's field investigations. The current version only discusses the seismogenic capacity of the Tehran Ray region but does not provide an overview of the tectonic setting of the entire tectonic belt.Therefore, the validity of the regional seismotectonic model based solely on fault strike requires additional background information on regional tectonic development (see Allen et al., 2003, JSGin detail);
Response: We have added the following to the Introduction:
The Alborz Mountain range in northern Iran occupies a key position within the broader Arabia-Eurasia collision zone, where oblique north–south convergence between the Arabian and Eurasian plates, compounded by westward motion of the South Caspian Basin, drives strain partitioning across the region (Allen et al., 2003). Oblique shortening in the range is accommodated through a combination of range-parallel left-lateral strike-slip faults and roughly N-S directed thrusting along faults dipping inward from the margins of the range. Allen et al. (2003) estimate approximately 30 km of crustal shortening across Alborz at the latitude of Tehran, and believe that the current kinematics (including the shift from right- to left-lateral faulting and onset of folding in South Caspian sediments) began in the Pliocene.
We have also added the following to the Discussion:
Despite a general consensus that south-dipping and north-dipping thrusts dominate the northern and southern parts of the Alborz Range, respectively (e.g., Allen et al., 2003), structural studies document major south-dipping thrusts in the southern external (foreland) parts of the range (see Fig. 12 in Allen et al., 2003; Fig. 10 in Ballato et al., 2008). These structures, whose geometry and kinematics are consistent with the Master Ray Fault, may represent north-vergent thrusts inherited from the early evolutionary stages of the Alborz thrust belt during the early Cenozoic.
- Regarding the coupling of deep and shallow structures, thrust faults, because their strike varies significantly across the cross-section, often appearing as shovel-like faults with a steeper upper portion and a gentler lower portion, whether the surface strike can be used to define the deep strike (and thus confirm the fault extension) is a question worth discussing. This requires support from high-resolution geophysical data. The reviewer emphasized that the paper needs to supplement the paper with deep geophysical data perpendicular to the fault strike in the Tehran region or adjacent areas (including citing other research results) to confirm the rationality of the coupling interpretation of the proposed tectonic model (Fig. 13).
Response: We have added the following to the Discussion:
The strike of the thrust faults in the piedmont region of Tehran varies to some degree due to two factors: 1) movement of the hanging wall on ramps, whose strikes (E–W) are oblique to the regional Quaternary shortening direction (NNE–SSW), and 2) the surficial thrust faults are in their embryonic stages of development; therefore, their strikes vary near their termination points to accommodate a decreasing gradient of displacement. Despite these variations, all studied thrust faults dip southward, and as shown by statistical analysis of folding in the A Unit (Fig. 2), the fault-related folding associated with the south-dipping thrusts displays a statistically well-defined E-W strike. Interestingly, the emergent fault segments in the piedmont region of Tehran exhibit an overlapping pattern similar to that suggested by Cartwright et al. (1995) for fault growth via segment linkage, eventually evolving into a single through-going fault. Our model for the extension of the piedmont fault into a single fault at depth (Fig. 13) may also be compared to the model for lateral propagation of blind thrust faults (see Fig. 4.38 in Burbank and Anderson, 2012).
The rapid sprawl of the Tehran Megacity, together with interference from ambient urban noise (traffic, etc.), hinders the acquisition of detailed, high-resolution geophysical data across the city. As a result, geophysical studies are generally limited to passive seismic data. A recent study of this type in Tehran (e.g., Soltani, 2023) illustrates an increasing depth to seismic bedrock beneath the A Unit, from the mountain front in the north toward the Ray area in the south - an observation that may partly support our model for the geometry of the Master Ray Fault and its connection to the thrust fault segments in the piedmont zone.
The aforementioned evidences, along with the lack of any thin-skinned tectonics associated with shallow décollement units, confirms that a major system of kinematically related south-dipping thrusts should connect and integrate into a single, major south-dipping fault at depth.
- Since the superficial structural deformation mentioned in Q2 above is only a "result" of focal activity, it is not itself thecauseof the earthquake. Therefore, if the model presented in the paper locates the earthquake source at a distance, the micro-epicenter will have deviated from the Tehran tectonic zone. The precise location of the minor earthquake currently presented does not demonstrate the validity of the model presented in this paper. Therefore, when revising the paper, the authors should carefully consider the universality of the regional tectonic model mentioned in Q1 and Q2 for local sections of the fault, and should not infer the overall tectonic characteristics from local sections.
Response: As you have rightly pointed out, the piedmont deformation structures are surface manifestations (results) of the cumulative effects of coseismic displacements generated during several major earthquakes within the seismogenic layer. As an independent line of evidence, we used the microseismicity of the Tehran region to constrain the south-dipping geometry of the Master Ray Fault. Admittedly, these foci are located away from the potential seismic source of the fault at depth to the south, but they may simply represent minor interseismic activity that generally occurs at shallow depths between major earthquakes at greater depths. A strong increase in the mean magnitude of earthquakes - with naturally longer return periods - towards greater depth has been reported in the continental crust of California and the Gulf of Corinth (e.g., Wyss et al., 2008).
In response to your comments, we have included in the revised version a discussion of the necessary cautions regarding the universality of our model, as follows:
We admit that the overall tectonic characteristics of southern Tehran region may not simply be inferred from the local sections in the piedmont zone, and the macroseismic foci, used to constrain the south-dipping geometry of the Master Ray Fault, are located away from the potential seismic source of the fault at depth to the south, but they may simply represent minor interseismic activity that generally occurs at shallow depths between major earthquakes at greater depths. A strong increase in the mean magnitude of earthquakes - with naturally longer return periods - towards greater depth has been reported in the continental crust of California and the Gulf of Corinth (e.g., Wyss et al., 2008).
- Regarding the uncertainty in the magnitude determination of historical strong earthquakes, recent studies of moderate-to-strong earthquakes with instrumental records and comprehensive damage investigations (see studies in Italy, China, Japan, the United States, etc.) have shown that damage near the epicenter of moderate earthquakes can also be severe. Therefore, the magnitudes of historical strong earthquakes calculated based on only a small amount of literature may generally be overstated (Ou et al., 2020, JGR: SE). Therefore, the estimated magnitudes of historical earthquakes cannot be equated with instrumentally recorded magnitudes, leading to discussions of regional substantial earthquake hazard without supporting seismic tectonic context.
Response: As you correctly advised, determining historical earthquake magnitudes is subject to major uncertainties. However, as we discussed in Section 6.1 of the manuscript, the city of Ray has been devastated by at least three major historical earthquakes. Despite these uncertainties, such events cannot be simply overlooked as possible evidence for a deep seismic source beneath the Ray region in southern Tehran. In the absence of a well-defined instrumental-period seismotectonic context for the Master Ray Fault, historical earthquake data remain the only seismic clues to the fault’s activity. Meanwhile, the south-dipping Quaternary faults in the piedmont zone are likely rooted at greater depths south of Tehran.
We have added the following paragraph to the end of the Introduction:
The occurrence of the 2003 Bam Earthquake, which caused more than 30,000 casualties (e.g., Berberian, 2005) in an area with no historical earthquake records but with a prominent Quaternary fault scarp, highlights the importance of investigating the surface manifestations of faults with long recurrence intervals and reassessing seismic hazards in urban areas in Iran and worldwide.
- Other minor issues: a) The paper lacks a summary of the regional tectonic context; this should be supplemented; b) Figure 1a in the paper lacks key place names; c) The field photos in the figure should be positioned on the map; they are currently incomplete; d) The discussion of historical earthquakes in the Discussion section is insufficiently detailed; a figure should be added; e) The rationale for the tectonic model in the Discussion section requires further discussion; f) The paper could supplement the regional tectonic model with a figure (which can be cited); g) some oral sentences should be deleted, for example: line 21: According to our analyses, line 55 According to our findings, line360 As explained under Section 2.
Response:
- a) The summary of the regional tectonics have been added to the Introduction as follows:
The Alborz Mountain Range in northern Iran occupies a key position within the broader Arabia-Eurasia collision zone, where oblique north–south convergence between the Arabian and Eurasian plates, compounded by westward motion of the South Caspian Basin, drives strain partitioning across the region (Allen et al., 2003). Oblique shortening in the range is accommodated through a combination of range-parallel left-lateral strike-slip faults and roughly N-S directed thrusting along faults dipping inward from the margins of the range. Allen et al. (2003) estimate approximately 30 km of crustal shortening across Alborz at the latitude of Tehran, and believe that the current kinematics (including the shift from right- to left-lateral faulting and onset of folding in South Caspian sediments) began in the Pliocene.
We have also added the following to the discussion:
Despite a general consensus that south-dipping and north-dipping thrusts dominate the northern and southern parts of the Alborz Range, respectively (e.g., Allen et al., 2003), structural studies document major south-dipping thrusts in the southern external (foreland) parts of the range (see Fig. 12 in Allen et al., 2003; Fig. 10 in Ballato et al., 2008). These structures, whose geometry and kinematics are consistent with the Master Ray Fault, may represent north-vergent thrusts inherited from the early evolutionary stages of the Alborz thrust belt during the early Cenozoic.
- b) The key places in Fig. 1b will be added to Fig. 1a.
- c) Location of all filed photos will be added to Fig. 1a.
- d) No figure is provided for the historical earthquake mentioned in the manuscript; readers are referred to Berberian and Yeats (2016) for details.
- e) The rationale for the tectonic model is elaborated in the Discussion.
- f) Since we do not intend to generalize our model to the entire southern Alborz Range in this manuscript, we believe that the details in Fig. 14, together with Fig. 2, provide the necessary information for our model.
- g) The manuscript has been revised to eliminate colloquial or conversational expressions.
References
Allen, M.B., Ghassemi, M.R., Shahrabi, M., and Qorashi, M., 2003. Accommodation of late Cenozoic oblique shortening in the Alborz range, northern Iran. Journal of Structural Geology, 25(5), 659–672.
Ballato, P., Nowaczyk, N.R., Landgraf, A., Strecker, M.R., Friedrich, A., and Tabatabaei, S.H., 2008. Tectonic control on sedimentary facies pattern and sediment accumulation rates in the Miocene foreland basin of the southern Alborz mountains, northern Iran. Tectonics, 27, TC6001, doi:10.1029/2008TC002278
Berberian, M., 2005, The 2003 Bam urban earthquake, a predictable seismotectonic pattern along the western margin of the rigid Lut block, southeast Iran: Earthquake Spectra, v. 21, no. S1, p. S35–S99, doi:10.1193/1.2127909.
Berberian, M., and Yeats, R.S., 2016. Tehran: An earthquake time bomb. In: Sorkhabi, R., (ed.), Tectonic Evolution, Collision, and Seismicity of Southwest Asia: In Honor of Manuel Berberian’s Forty-Five Years of Research Contributions: Geological Society of America Special Paper 525, p. 1–84, doi:10.1130/2016.2525(04)
Burbank, D.W., and Anderson, R.S., 2012. Tectonic geomorphology. Wiley-Blackwell, Second Edition, 454 p.
Cartwright, J.A., Trudgill, B.D., and Mansfield, C.S., 1995. Fault growth by segment linkage: an explanation for scatter in maximum displacement and trace length data from the Canyonlands grabens of SE Utah. Journal of Structural Geology, 17, 1319–1326.
Soltani, S., 2023. 3D modeling of the Tehran sedimentary basin: impact on seismic risk assessment. Applied geology. Ph.D. Thesis, Université Grenoble Alpes; International Institute of Earthquake Engineering and Seismology, 242 p.
Wyss, M., Pacchiani, F., Deschamps, A., and Patau, G., 2008. Mean magnitude variations of earthquakes as a function of depth: Different crustal stress distribution depending on tectonic setting. Geoph. Res. Lett., 35, L01307, doi:10.1029/2007GL031057
Citation: https://doi.org/10.5194/egusphere-2025-500-AC1
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AC1: 'Reply on RC1', Mohammad R. Ghassemi, 22 Sep 2025
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RC2: 'Comment on egusphere-2025-500', Anonymous Referee #2, 13 Aug 2025
Review on “Active Piedmont Zone Deformation, a manifestation of activity on the ‘Master Ray Fault’; insight into the seismic hazard analysis of the Tehran metropolitan area” coauthored by Ghassemi and Heydari
This paper studies several south-dipping piedmont faults in Tehran region and relates them to a possible low-angle south-dipping Rey master fault. The authors first describe the geomorphology and evidence of active faulting of the piedmont faults. They notice that the faults have traces in different directions and their surface trace is rather irregular. In the second step, for the first time they date the active faulting in Chitgar fault zone using Luminescence dating of unit B and calculate a shortening rate for the fault zone. In the third step, the authors use locally recorded micro-seismicity and notice that the depth of the earthquakes gradually increases towards south. Using this observation, they conclude that the south-dipping piedmont faults are actually connected to a south-dipping low angle master fault, the Rey fault. They then use their slip rates calculated for the faults in Chitgar fault zone to infer possible slip rates on the reverse master Rey fault. I think the paper should consider the following important points before being publishable in EGUsphere.
- Authors do not try to put their interpretation on a regional scale. For example, they do not state what is the general direction of sigma1 (maximum principal stress) in the region. We know from GPS (Khorrami et al., 2019) (Banimahdi Dehkordi et al., 2024b) and also focal mechanisms recently published by (Banimahdi Dehkordi et al., 2024a) the direction of sigma1 is NE-SW. Such a sigma1 direction cannot result to dominantly reverse mechanisms on Rey and other piedmont fault and one expect to have mostly strike-slip motion on these faults. So there is a need for authors to put their findings into a larger frame and try to discuss how it relates to recent detail seismological and geodetical findings in the region.
- One of the main pieces of evidence for the proposal of the Rey master fault is the observed southward increase in depth of microseismicity. The authors did not consider possible systematic errors in the determination of focal depths. Essentially, to have a reliable focal depth determination, the event should have been recorded by a local network with good azimuthal coverage and also at least recorded by a seismic station at distances not greater than one to 1.5 times of focal depth. Looking into the seismic station of Iranian Seismological Center (irsc.ut.ac.ir), one can quickly realize that the station density is not good enough to record reliably the focal depth of most of the events. The precisely relocated seismicity of Tehran (Banimahdi Dehkordi et al., 2024a) shows that the microseismicity is actually happening to the east of the proposed Master Rey fault. Therefore, I would say that the observed seismicity does not support nor disprove the existence of the master Rey fault.
- It is not clear if the state of stress throughout 137-364 ka ago have been constant. Maybe the active faulting belongs to older times when the direction of sigma1 was different than now and for now the faults are not active at all and that is why they lack any seismicity over thirty year of activity of Tehran seismic network. I should say that even the dense seismic network of Tehran municipality did not detect any noticeable seismicity on these studies faults.
- It is required to show better the geometrical relationship between the thrust fault and the assumed Rey Master fault. To do so please put distance on Figure 13. By the way the Rey fault itself has two main branches, the north and south Rey fault, which one authors relate to the master Ray fault and why?
Minor comments:
- There are ongoing controversy on whether some of the active faults mentioned in this work are indeed an active fault or not! It is essential to review those views and somehow discuss them.
- The authors insist on North Tehran fault (NTF) being as mostly north-dipping thrust fault. This conclusion comes from a recent paper by the first author. Others (Tchalenko, 1975) (Abbassi and Farbod, 2009) have shown that the NTF is mostly en-echelon strike-slip fault. Sigma1 direction and general azimuth of the fault also imply a mostly strike-slip fault. Please consider other views better.
- Please show the Rey and Kahrizak faults on one of your maps.
- On line 87, authors say that “Most transpressional deformation is accommodated by the range-parallel thrust and left-lateral strike-slip structures, such as the NTF, Caspian Fault and Mosha Fault.” This is the most popular view on Alborz but looking into the recent updated seismicity and focal mechanism shows almost very little seismicity on Caspian fault, and pronounced seismicity on North Alborz fault. Additionally, the thrust faults and strike-slip faults are not parallel and also thrust and strike-slip events happened everywhere and thus there is no indication of strain-partitioning (Banimahdi Dehkordi et al., 2024a,b). Due to lack of enough GPS stations, all previous GPS models indicate a large slip on Khazar fault but addition of new GPS stations reveal significant slip on North Alborz fault zone and a much reduced slip rate on Khazar fault.
- On line 92: Now Tehran has several instrumentally recorded earthquakes of larger than magnitude 4 like Mallard 2017/12 earthquake.
- Line 359: I know in this region, there is lots of mine blasts. Usually these mine blasts have magnitudes less than 2 Mn. So please remove all those events less than 2 Mn.
- It is not clear how samples from B units in Chitgar fault can reveal age of active faulting there. Please explain this thoroughly.
References:
Abbassi, M.R., Farbod, Y., 2009. Faulting and folding in quaternary deposits of Tehran’s piedmont (Iran). J. Asian Earth Sci. 34, 522–531. https://doi.org/10.1016/j.jseaes.2008.08.001
Banimahdi Dehkordi, M.J., Ghods, A., Shabanian, E., Mousavi, Z., 2024a. Constraint on the active tectonics of the Alborz using seismology data. Iran. J. Geophys.
Banimahdi Dehkordi, M.J., Mousavi, Z., Shabanian, E., Abbasi, M., Ghods, A., 2024b. Constraint on the active tectonics of the Alborz (Iran) using geodetic data. Iran. J. Geophys. 18, 55–76.
Khorrami, F., Vernant, P., Masson, F., Nilfouroushan, F., Mousavi, Z., Nankali, H., Saadat, S.A., Walpersdorf, A., Hosseini, S., Tavakoli, P., Aghamohammadi, A., Alijanzade, M., 2019. An up-to-date crustal deformation map of Iran using integrated campaign-mode and permanent GPS velocities. Geophys. J. Int. 217, 832–843. https://doi.org/10.1093/gji/ggz045
Tchalenko, J.S., 1975. Seismotectonic framwork of the North Tehran Fault. Tectonophysics 29, 411–420.
Citation: https://doi.org/10.5194/egusphere-2025-500-RC2 -
AC2: 'Reply on RC2', Mohammad R. Ghassemi, 22 Sep 2025
Reviewer #2
Review on “Active Piedmont Zone Deformation, a manifestation of activity on the ‘Master Ray Fault’; insight into the seismic hazard analysis of the Tehran metropolitan area” coauthored by Ghassemi and Heydari
This paper studies several south-dipping piedmont faults in Tehran region and relates them to a possible low-angle south-dipping Rey master fault. The authors first describe the geomorphology and evidence of active faulting of the piedmont faults. They notice that the faults have traces in different directions and their surface trace is rather irregular. In the second step, for the first time they date the active faulting in Chitgar fault zone using Luminescence dating of unit B and calculate a shortening rate for the fault zone. In the third step, the authors use locally recorded micro-seismicity and notice that the depth of the earthquakes gradually increases towards south. Using this observation, they conclude that the south-dipping piedmont faults are actually connected to a south-dipping low angle master fault, the Rey fault. They then use their slip rates calculated for the faults in Chitgar fault zone to infer possible slip rates on the reverse master Rey fault. I think the paper should consider the following important points before being publishable in EGUsphere.
Response: We sincerely appreciate the insightful feedback from Reviewer RC2. Our responses are provided following each numbered comment.
- Authors do not try to put their interpretation on a regional scale. For example, they do not state what is the general direction of sigma1 (maximum principal stress) in the region. We know from GPS (Khorrami et al., 2019) (Banimahdi Dehkordi et al., 2024b) and also focal mechanisms recently published by (Banimahdi Dehkordi et al., 2024a) the direction of sigma1 is NE-SW. Such a sigma1 direction cannot result to dominantly reverse mechanisms on Rey and other piedmont fault and one expect to have mostly strike-slip motion on these faults. So there is a need for authors to put their findings into a larger frame and try to discuss how it relates to recent detail seismological and geodetical findings in the region.
Response: We present our reply through five lines of evidence:
1) Stress regime from earthquake focal mechanisms: Inversion of earthquake focal mechanisms suggests a NE–SW maximum stress direction for the central Alborz range (e.g., Pourbiranvand, 2018). Simple resolving of this stress regime on E–W striking fault planes, such as the Master Ray Fault, would result in oblique thrust-left-lateral kinematics. However, as widely accepted by many researchers (e.g., Allen et al., 2003), strain (and therefore stress) in the Alborz region is generally partitioned between thrust and strike-slip faults.
2) Geodetic evidence for variable strain directions: Geodetic studies by Masson et al. (2014) indicate a local change in the maximum principal strain tensor direction from NE to NW near the longitude of Tehran. Similarly, Khorrami et al. (2018) documented an almost N–S-trending local principal strain tensor direction south of Tehran.
3) Role of the Master Ray Fault: As noted in our manuscript, the Master Ray Fault is interpreted as an inherited bedrock structure that now accommodates shortening in the Tehran region primarily via thrust faulting.
4) Evidence of E-W strike-slip faults: We have also identified several E–W striking strike-slip faults parallel to the surface trace of the Master Ray Fault (please see Fig. 1). These structures appear to accommodate the partitioning of oblique shortening in the region, consistent with the regime described in (1).
5) Geodetic balance of thrust and strike-slip components: Analysis of geodetic data from the Alborz region (Banimahdi-Dehkordi et al., 2024a, b) indicates that the fault-perpendicular (thrust) component of shortening across the central Alborz, including the Tehran region, is comparable in magnitude to the strike-slip component.
- One of the main pieces of evidence for the proposal of the Rey master fault is the observed southward increase in depth of microseismicity. The authors did not consider possible systematic errors in the determination of focal depths. Essentially, to have a reliable focal depth determination, the event should have been recorded by a local network with good azimuthal coverage and also at least recorded by a seismic station at distances not greater than one to 1.5 times of focal depth. Looking into the seismic station of Iranian Seismological Center (irsc.ut.ac.ir), one can quickly realize that the station density is not good enough to record reliably the focal depth of most of the events. The precisely relocated seismicity of Tehran (Banimahdi Dehkordi et al., 2024a) shows that the microseismicity is actually happening to the east of the proposed Master Rey fault. Therefore, I would say that the observed seismicity does not support nor disprove the existence of the master Rey fault.
Response: The relocated seismicity reported by Banimahdi-Dehkordi et al. (2024a) pertains to a much larger region beyond the Tehran region, encompassing events with magnitudes of 3 and greater. In contrast, our dataset focuses on microseismicity within the Tehran region, with magnitudes ranging from 1.0 to 2.9. We evaluated the best-fit surface to the focal depths of these microearthquakes and argue that, despite uncertainties in focal depth determinations, the shallow southward dip of the surface can account for these errors when considering the statistical distribution of the abundant small events.
- It is not clear if the state of stress throughout 137-364 ka ago have been constant. Maybe the active faulting belongs to older times when the direction of sigma1 was different than now and for now the faults are not active at all and that is why they lack any seismicity over thirty year of activity of Tehran seismic network. I should say that even the dense seismic network of Tehran municipality did not detect any noticeable seismicity on these studies faults.
Response: Any modeling of slip-rate measurements on active faults necessarily involves assumptions, such as constant kinematics and a uniform slip rate for the studied fault(s) during the period under study. Following the reviewer’s comment to its logical conclusion would imply that no slip-rate estimation could be considered valid if it relies on absolute dating older than a few hundred thousand years, regardless of location.
- It is required to show better the geometrical relationship between the thrust fault and the assumed Rey Master fault. To do so please put distance on Figure 13. By the way the Rey fault itself has two main branches, the north and south Rey fault, which one authors relate to the master Ray fault and why?
Response: We have added the longitude and latitude in addition to depth in Figure 14. Regarding the North and South Ray Faults, we consider these to be minor backthrusts in the hanging wall of the Master Ray Fault. Therefore, we use the term “Master Ray Fault” to distinguish this major structure from the two minor faults.
Minor comments:
- There are ongoing controversy on whether some of the active faults mentioned in this work are indeed an active fault or not! It is essential to review those views and somehow discuss them.
Response: We are aware of the controversy surrounding the Kahrizak, North Ray, and South Ray Faults, particularly regarding the interpretation of their prominent scarps as paleolake shorelines. The scope of the present manuscript does not allow us to address this misinterpretation in detail; however, the authors have already submitted a separate manuscript that challenges these interpretations based on field data and geomorphological analyses.
- The authors insist on North Tehran fault (NTF) being as mostly north-dipping thrust fault. This conclusion comes from a recent paper by the first author. Others (Tchalenko, 1975) (Abbassi and Farbod, 2009) have shown that the NTF is mostly en-echelon strike-slip fault. Sigma1 direction and general azimuth of the fault also imply a mostly strike-slip fault. Please consider other views better.
Response: Although not central to our manuscript, we have taken into account the interpretations of Tchalenko (1975) and Abbassi and Farbod (2009) regarding the kinematics of the NTF. It should also be noted that at least 2.5 km of uplift has occurred in the hangingwall of the NTF as a thrust fault Tchalenko (1975), whereas estimates of strike-slip displacement along this fault appear to be much smaller.
We have added the following lines to Introduction:
While there is evidence for left-lateral strike-slip movement on the NTF (e.g., Tchalenko, 1975; Abbassi and Farbod, 2009), the faults also show a substantial reverse dip-slip component, estimated to be at least 2.5 km based on the minimum uplift of the hanging-wall rocks (Tchalenko, 1975).
- Please show the Rey and Kahrizak faults on one of your maps.
Response: We have shown the North Ray, South Ray and Kahrizak Faults on Fig. 13a.
- On line 87, authors say that “Most transpressional deformation is accommodated by the range-parallel thrust and left-lateral strike-slip structures, such as the NTF, Caspian Fault and Mosha Fault.” This is the most popular view on Alborz but looking into the recent updated seismicity and focal mechanism shows almost very little seismicity on Caspian fault, and pronounced seismicity on North Alborz fault. Additionally, the thrust faults and strike-slip faults are not parallel and also thrust and strike-slip events happened everywhere and thus there is no indication of strain-partitioning (Banimahdi Dehkordi et al., 2024a,b). Due to lack of enough GPS stations, all previous GPS models indicate a large slip on Khazar fault but addition of new GPS stations reveal significant slip on North Alborz fault zone and a much reduced slip rate on Khazar fault.
Response: We have incorporated the recent interpretations on the activity of the Caspian (Khazar) Fault and the North Alborz Fault by Banimahdi-Dehkordi et al. (2024a, b) into the relevant section of the manuscript as follows:
A recent study on seismicity and focal mechanisms in the central Alborz region (Banimahdi-Dehkordi et al., 2024a, b) suggests minor seismicity along the Caspian Fault and pronounced seismicity along the North Alborz Fault. The authors also argue that there is no evidence of strain partitioning in the region. According to the study, significant slip occurs on the North Alborz Fault zone compared to the Caspian Fault.
- On line 92: Now Tehran has several instrumentally recorded earthquakes of larger than magnitude 4 like Mallard 2017/12 earthquake.
Response: We have added the account of the Malard event to line 92 as follows:
Light earthquakes, with a maximum magnitude of 4.8 (Mw), were reported only in the west and northeast of the Tehran metropolitan area during the 2017 Malard and 2020 Damavand events, respectively (Niazpour and Shomali, 2024).
- Line 359: I know in this region, there is lots of mine blasts. Usually these mine blasts have magnitudes less than 2 Mn. So please remove all those events less than 2 Mn.
Response: Most of the mining blasts originate from the bedrock outcrops located east of longitude 51.5°E; please see the extent of the seismicity map in Figure 13.
- It is not clear how samples from B units in Chitgar fault can reveal age of active faulting there. Please explain this thoroughly.
Response: We have added this discussion to the relevant section of the manuscript:
As illustrated in Figure 9d, the faulted B Unit is carried within the hangingwall of the Chitgar Thrust Fault. Some of the normal faults in this unit were later inverted during compressional (thrust) faulting episode, indicating that they predate the initiation of the Chitgar Thrust Fault. However, the hangingwall of the fault was subsequently cut at the footwall ramp, with a minimum displacement of 68 m following an earlier phase of 1047 m of movement on the fault. Therefore, we used the post-B Unit displacement value to estimate the minimum slip rate, based on the oldest age of the unit determined from luminescence dating.
References:
Abbassi, M.R., Farbod, Y., 2009. Faulting and folding in quaternary deposits of Tehran’s piedmont (Iran). J. Asian Earth Sci. 34, 522–531. https://doi.org/10.1016/j.jseaes.2008.08.001
Banimahdi Dehkordi, M.J., Ghods, A., Shabanian, E., Mousavi, Z., 2024a. Constraint on the active tectonics of the Alborz using seismology data. Iran. J. Geophys.
Banimahdi Dehkordi, M.J., Mousavi, Z., Shabanian, E., Abbasi, M., Ghods, A., 2024b. Constraint on the active tectonics of the Alborz (Iran) using geodetic data. Iran. J. Geophys. 18, 55–76.
Khorrami, F., Vernant, P., Masson, F., Nilfouroushan, F., Mousavi, Z., Nankali, H., Saadat, S.A., Walpersdorf, A., Hosseini, S., Tavakoli, P., Aghamohammadi, A., Alijanzade, M., 2019. An up-to-date crustal deformation map of Iran using integrated campaign-mode and permanent GPS velocities. Geophys. J. Int. 217, 832–843. https://doi.org/10.1093/gji/ggz045
Tchalenko, J.S., 1975. Seismotectonic framework of the North Tehran Fault. Tectonophysics 29, 411–420.
References
Allen, M.B., Ghassemi, M.R., Shahrabi, M., and Qorashi, M., 2003. Accommodation of late Cenozoic oblique shortening in the Alborz range, northern Iran. Journal of Structural Geology, 25(5), 659–672.
Banimahdi Dehkordi, M.J., Ghods, A., Shabanian, E., Mousavi, Z., 2024a. Constraint on the active tectonics of the Alborz using seismology data. Iran. J. Geophys.
Banimahdi Dehkordi, M.J., Mousavi, Z., Shabanian, E., Abbasi, M., Ghods, A., 2024b. Constraint on the active tectonics of the Alborz (Iran) using geodetic data. Iran. J. Geophys. 18, 55–76.
Khorrami, F., Vernant, P., Masson, F., Nilfouroushan, F., Mousavi, Z., Nankali, H., Saadat, S, A., Walpersdorf,7 A., Hosseini, S., Tavakoli, P., Aghamohammadi, A., Alijanzade, M., 2019. An up-to-date crustal deformation map of Iran using integrated campaign-mode and permanent GPS velocities Geophys. J. Int. 217, 832–843 doi: 10.1093/gji/ggz045
Masson, F., Lehujeur, M., Ziegler, Y., and Doubre, C., 2014. Strain rate tensor in Iran from a new GPS velocity field, Geophys. J. Int., 197, 10–21.
Niazpour, B., and Shomali, Z.H., 2024. Moderate earthquakes striking Tehran metropolitan area: a case study of 2017 Malard and 2020 Damavand seismic sequences. Journal of Seismology, 28, 103-117, https://doi.org/10.1007/s10950-023-10187-z
Pourbeyranvand, S., 2018. Stress studies in the Central Alborz by inversion of earthquake focal mechanism data. Acta Geophysica, https://doi.org/10.1007/s11600-018-0207-1
Citation: https://doi.org/10.5194/egusphere-2025-500-AC2
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RC3: 'Comment on egusphere-2025-500', Anonymous Referee #3, 21 Aug 2025
The manuscript addresses active faulting and seismic hazard in the Tehran metropolitan area, focusing on five south-dipping thrust faults and introducing the “Master Ray Fault” as a new potential seismogenic source. The topic is highly relevant for understanding seismic hazards in one of the most densely populated regions of Iran. However, the paper currently suffers from conceptual ambiguities, insufficient methodological rigor, and weak figure presentation. The overall structure and writing style resemble a technical report rather than a concise scientific article, ‘cause except for seismic risk analysis for some active faults, I really do not get the authors’ scientific questions. Significant revisions are required to enhance clarity, rigor, and scientific impact.
Major Issues
- Title and Scope
- The title includes a semicolon (“;”), which is unconventional for scientific articles. It should be reformulated into a concise and informative title.
- The scope of the paper is not well defined: is the main contribution a new fault model (“Master Ray Fault”), a methodological framework, or a regional seismic hazard reassessment?
- Scientific Purpose and Rationale
- The abstract claims that “multi-patterned deformation in the piedmont zone unravels seismic sources.” This correlation between surface deformation and deep seismogenic sources is not convincingly established. A clear methodological or theoretical framework is missing.
- The introduction lacks a well-structured research question or hypothesis. The reader is left uncertain about the central scientific aim.
- Study Area Definition
- The location of the investigated faults within the broader tectonic framework of the Alborz and Iranian Plateau is not sufficiently illustrated.
- A clear area of interest (AOI) map is needed, showing the relation of the investigated faults to the North Tehran Fault and other regional structures.
- Slip Rate Estimates and OSL Dating
- Slip rates are reported with vague qualifiers such as “ca. 0.5 mm/yr.” Uncertainty bounds and methodological details are missing.
- OSL dating results (Table 1) approach signal saturation and are explicitly acknowledged by the authors as possibly underestimated. Using these to derive slip rates is problematic without further validation.
- Error propagation in slip rate estimates is not properly addressed.
- Figures and Cartography
- Figures are of insufficient quality for publication. Some appear as low-resolution screenshots (e.g., Fig. 10b, 10c).
- Stratigraphic units labeled as “A Unit,” “C Unit,” etc., are confusing without a proper stratigraphic framework.
- Several figures (e.g., Fig. 5b) contain unnecessary labels that distract from the main observations.
- High-resolution, publication-quality figures prepared in GIS/Illustrator are required.
- Earthquake Catalog and Microseismicity
- The microseismicity analysis (Fig. 12) is problematic. It is not clear whether events were relocated. Without robust relocation, reported depths may have uncertainties >5–10 km, making interpretations of seismogenic layering unreliable.
- The polynomial fitting of hypocenters is not a robust method to infer fault geometry.
- Inconsistency with Regional Tectonics
- The model of a major south-dipping “Master Ray Fault” contradicts many previous studies that emphasize north-dipping thrusts as the dominant structures in the Alborz.
- The authors need to reconcile their interpretation with GPS shortening rates (4–5 mm/yr across Alborz) and with prior fault-kinematic models.
- Historical Earthquake Correlation
- The proposed association between the “Master Ray Fault” and destructive historical earthquakes (e.g., AD 855, AD 864) is speculative and lacks paleoseismological evidence.
- More rigorous evidence (archaeoseismology, trenching, historical intensity reanalysis) is required to substantiate this claim.
- Manuscript Structure and Writing
- The manuscript reads more like a technical report than a journal article. Organization is weak, logic is inconsistent, and redundant descriptions reduce clarity.
- A clearer, hypothesis-driven narrative is needed.
Minor Issues
- Terminology such as “north-vergent thrusting” and “south-dipping thrusts” is inconsistently applied and may confuse readers. A standardized terminology is recommended.
- Several grammatical and typographical errors remain (e.g., “ca.” used improperly, inconsistent tense usage). Careful proofreading is required.
- References to stratigraphic units (A, B, C) should be explained in more detail, preferably with a stratigraphic column figure or geological group name.
- Some statements in the introduction are overly general and not directly linked to the study (e.g., discussion of foreland basin systems). Streamlining would improve readability.
Recommendation
Given the current conceptual weaknesses, methodological issues, poor figure quality, and organizational problems, I recommend Rejection in its present form. A future submission could be reconsidered only if the authors:
- Provide robust evidence for the existence and geometry of the proposed “Master Ray Fault,”
- Improve chronological and slip rate analyses with better treatment of uncertainties,
- Relocate earthquake data and apply more rigorous seismological methods,
- Produce publication-quality figures,
- Rewrite the manuscript with a clear scientific hypothesis and logical structure.
Citation: https://doi.org/10.5194/egusphere-2025-500-RC3 -
AC3: 'Reply on RC3', Mohammad R. Ghassemi, 22 Sep 2025
Reviewer #3
The manuscript addresses active faulting and seismic hazard in the Tehran metropolitan area, focusing on five south-dipping thrust faults and introducing the “Master Ray Fault” as a new potential seismogenic source. The topic is highly relevant for understanding seismic hazards in one of the most densely populated regions of Iran. However, the paper currently suffers from conceptual ambiguities, insufficient methodological rigor, and weak figure presentation. The overall structure and writing style resemble a technical report rather than a concise scientific article, ‘cause except for seismic risk analysis for some active faults, I really do not get the authors’ scientific questions. Significant revisions are required to enhance clarity, rigor, and scientific impact.
Response: We acknowledge the comments provided by Reviewer RC3 and address each point in detail below.
Major Issues
- Title and Scope
The title includes a semicolon (“;”), which is unconventional for scientific articles. It should be reformulated into a concise and informative title.
Response: The semicolon in the title was an oversight that have been modified in the revised version.
The scope of the paper is not well defined: is the main contribution a new fault model (“Master Ray Fault”), a methodological framework, or a regional seismic hazard reassessment?
Response: As outlined in the Abstract, Introduction, Discussion, and Conclusion, our main contribution is the identification of the Master Ray Fault as a major seismic source for the densely populated Tehran region, proposed here for the first time to explain the enigmatic south-dipping structures in the piedmont zone.
Scientific Purpose and Rationale
The abstract claims that “multi-patterned deformation in the piedmont zone unravels seismic sources.” This correlation between surface deformation and deep seismogenic sources is not convincingly established. A clear methodological or theoretical framework is missing.
Response: The piedmont zones in front of active mountain belts host Quaternary alluvial and colluvial deposits, which have strong potential for recording recent movements along active faults and folds as surface expressions of deep, previously unexplored seismic sources. Our methodology is clearly described in lines 46–54 of the Introduction.
The introduction lacks a well-structured research question or hypothesis. The reader is left uncertain about the central scientific aim.
Response: A more detailed research question have been added to the Introduction as follows:
“Our major research questions are: How do the geometry, kinematics, and slip rates of active south-dipping thrust faults in the Tehran piedmont zone influence the seismic hazard assessment of the metropolitan area, and what role might a potential master fault at depth play?”Study Area Definition
The location of the investigated faults within the broader tectonic framework of the Alborz and Iranian Plateau is not sufficiently illustrated.
A clear area of interest (AOI) map is needed, showing the relation of the investigated faults to the North Tehran Fault and other regional structures.
Response: A new Figure 1 have been added to the manuscript, which includes the required regional data.
Slip Rate Estimates and OSL Dating
Slip rates are reported with vague qualifiers such as “ca. 0.5 mm/yr.” Uncertainty bounds and methodological details are missing.
Response: The uncertainty on each reported slip rate have been stated in the revised version of our manuscript.
OSL dating results (Table 1) approach signal saturation and are explicitly acknowledged by the authors as possibly underestimated. Using these to derive slip rates is problematic without further validation.
Response: The methodological limits of our method are clearly outlined in our manuscript. Respectfully, we disagree with the statement that “...using these to derive slip rates is problematic without further validation.” Every scientific method has its limits; we presented the most probable analysis. The absence of another validation, however, does not invalidate our measurements per se.
Error propagation in slip rate estimates is not properly addressed.
Response: We agree that the uncertainties should be better quantified in the main text, which have been done in a revised version of our manuscript.
Figures and Cartography
Figures are of insufficient quality for publication. Some appear as low-resolution screenshots (e.g., Fig. 10b, 10c).
Response: Unfortunately, we cannot reproduce this observation. For instance, the flagged Fig. 10b/10c is based on vector graphics, embedded as raster graphics in the produced PDF. Blurring caused by the raster compression algorithm would become visible only for a magnification of more than 400%.
To avoid dismissing your comment too easily, we have asked a colleague for a second opinion, but the result remains the same. We would also like to mention that the graphical figure quality is verified by Copernicus after upload, before opening the discussion; they did not flag any issues either.
Our map had been created with Corel Draw software, as it is standard in geoscience.
Stratigraphic units labeled as “A Unit,” “C Unit,” etc., are confusing without a proper stratigraphic framework.
Response: As for the figure’s unnecessary labels, such as the mentioned Fig. 5, we cannot follow this comment. The figure contains only the minimum set of labels we find essential for understanding. Is there something particular you find distracting?
Several figures (e.g., Fig. 5b) contain unnecessary labels that distract from the main observations.
Response: We have added Fig. 4c following the advice of the handling editor.
High-resolution, publication-quality figures prepared in GIS/Illustrator are required.
Response: We refer to our response regarding the equality of the figures above.
Earthquake Catalog and Microseismicity
The microseismicity analysis (Fig. 12) is problematic. It is not clear whether events were relocated. Without robust relocation, reported depths may have uncertainties >5–10 km, making interpretations of seismogenic layering unreliable.
The polynomial fitting of hypocenters is not a robust method to infer fault geometry.
Response: We evaluated the best-fit surface to the focal depths of these microearthquakes using polynomial fitting, and we argue that, despite uncertainties in focal depth determinations, the shallow southward dip of the surface can account for these errors when considering the statistical distribution of the abundant small events.
Inconsistency with Regional Tectonics
The model of a major south-dipping “Master Ray Fault” contradicts many previous studies that emphasize north-dipping thrusts as the dominant structures in the Alborz.
Response: We have added the following to the discussion:
Despite a general consensus that south-dipping and north-dipping thrusts dominate the northern and southern parts of the Alborz Range, respectively (e.g., Allen et al., 2003), structural studies document major south-dipping thrusts in the southern external (foreland) parts of the range (see Fig. 12 in Allen et al., 2003; Fig. 10 in Ballato et al., 2008). These structures, whose geometry and kinematics are consistent with the Master Ray Fault, may represent north-vergent thrusts inherited from the early evolutionary stages of the Alborz thrust belt during the early Cenozoic.
The authors need to reconcile their interpretation with GPS shortening rates (4–5 mm/yr across Alborz) and with prior fault-kinematic models.
Response: We have revised Section 2 of the manuscript to include the kinematic framework of the Tehran region as indicated by geodetic studies.
Historical Earthquake Correlation
The proposed association between the “Master Ray Fault” and destructive historical earthquakes (e.g., AD 855, AD 864) is speculative and lacks paleoseismological evidence.
More rigorous evidence (archaeoseismology, trenching, historical intensity reanalysis) is required to substantiate this claim.
Response: Our work represents a new stepping stone toward a better understanding of unexplored seismic sources in a large metropolitan area; further paleoseismological and archaeoseismological studies of the piedmont zone faults and historical sites could provide a clearer validation of our model.
Manuscript Structure and Writing
The manuscript reads more like a technical report than a journal article. Organization is weak, logic is inconsistent, and redundant descriptions reduce clarity.
Response: We respectfully disagree with this assessment. While our manuscript contains detailed geological descriptions necessary for documenting new structural and seismotectonic observations, it is organized and framed in line with the standards of a research article rather than a technical report. Specifically:
Clear Research Question and Contribution: The manuscript does not simply describe local geology; it advances a new conceptual framework by introducing the “Master Ray Fault” as a significant seismogenic source for the Tehran region. This represents a novel scientific interpretation with implications for seismic hazard assessment, which goes beyond the scope of a technical report.
Scientific Structure: The manuscript follows the conventional structure of a research paper, including Abstract, Introduction, Geological and Tectonic Framework, Methods (e.g., luminescence dating, structural analysis), Results (fault mapping, microseismicity), Discussion (kinematic implications, comparison with previous models), and Conclusion. This structure is consistent with the publication standards of international geology and seismotectonics journals.
Analytical and Interpretive Approach: Rather than compiling descriptive data, our study integrates geomorphic, structural, geochronological, and seismic datasets to interpret fault kinematics and quantify slip rates. The logical flow from data collection to regional tectonic interpretation ensures the work is analytical, not merely descriptive.
Conciseness and Clarity: While the study necessarily includes technical detail to ensure reproducibility, we have taken care to minimize redundancy and avoid the style of an engineering “report.” We are, however, open to streamlining specific sections if the editorial team feels further tightening would enhance clarity.
In summary, our work is framed as an original contribution to fault kinematics and seismic hazard assessment, consistent with journal standards. It presents a novel model for the Tehran piedmont zone and introduces a previously unrecognized major fault system. We therefore believe the manuscript is appropriate in scope, style, and structure for publication in a peer-reviewed journal.
A clearer, hypothesis-driven narrative is needed.
Response: A more detailed research question have been added to the introduction as follows:
“How do the geometry, kinematics, and slip rates of active south-dipping thrust faults in the Tehran piedmont zone influence the seismic hazard assessment of the metropolitan area, and what role might a potential master fault at depth play?”Minor Issues
Terminology such as “north-vergent thrusting” and “south-dipping thrusts” is inconsistently applied and may confuse readers. A standardized terminology is recommended.
Response: Throughout the manuscript, we used the suffix ‘-dipping’ when referring to fault geometry and ‘-vergent’ when referring to fault kinematics.
Several grammatical and typographical errors remain (e.g., “ca.” used improperly, inconsistent tense usage). Careful proofreading is required.
Response: We have proofread the revised manuscript to remove grammatical and typographical errors.
References to stratigraphic units (A, B, C) should be explained in more detail, preferably with a stratigraphic column figure or geological group name.
Response: To avoid increasing the length of the manuscript, we have referred readers to Ghassemi (2023) for a detailed stratigraphy of these units under Section 2.
Some statements in the introduction are overly general and not directly linked to the study (e.g., discussion of foreland basin systems). Streamlining would improve readability.
Response: The emphasis on foreland basin systems in the Introduction is to acquaint the audience with the regional tectonic setting of the piedmont areas and the relevance of our study to a global problem.
Recommendation
Given the current conceptual weaknesses, methodological issues, poor figure quality, and organizational problems, I recommend Rejection in its present form. A future submission could be reconsidered only if the authors:
- Provide robust evidence for the existence and geometry of the proposed “Master Ray Fault,”
Response: We believe that our approach for introducing the Master Ray Fault and its activity is well-supported by the existing results and the amendments described in our replies.
- Improve chronological and slip rate analyses with better treatment of uncertainties,
Response: We have refined the calculated slip rates by incorporating uncertainty values.
- Relocate earthquake data and apply more rigorous seismological methods,
Response: Relocating microseismic events with magnitudes between 0.9 and 1.0 recorded by a regional network is a separate, challenging task, which was not the primary focus of this study.
- Produce publication-quality figures,
Response: The poor quality of some images likely occurred during the conversion of the manuscript file to PDF format. We will improve the images as you have requested.
- Rewrite the manuscript with a clear scientific hypothesis and logical structure.
Response: The scientific hypothesis and research question have been added to the introduction.
Citation: https://doi.org/10.5194/egusphere-2025-500-AC3
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- 1
This submitted manuscript proposes a new regional seismotectonic model for the region near the capital city of Tehran, Iran, based on field surveys, remote sensing interpretation, and a catalog of instrumentally recorded earthquakes. Based on observed variations in the strike of some thrust faults, the paper concludes that the "Master Ray Fault" can explain the seismogenic tectonic setting of the Tehran region's magnitude > 7 earthquakes and that tectonic explanations can also explain several historical strong earthquakes. Discussing this regional tectonic model is crucial for understanding the patterns of historical strong earthquakes and the potential for future strong earthquake hazards. While the paper has made some progress, several scientific issues remain that require further discussion and refinement:
1. The collision of the Arabian and Eurasian plates controls the regional tectonic model for northern Iran. The surface deformation generated by the south-to-north thrust in this region is the subject of the paper's field investigations. The current version only discusses the seismogenic capacity of the Tehran Ray region but does not provide an overview of the tectonic setting of the entire tectonic belt. Therefore, the validity of the regional seismotectonic model based solely on fault strike requires additional background information on regional tectonic development (see Allen et al., 2003, JSG in detail);
2. Regarding the coupling of deep and shallow structures, thrust faults, because their strike varies significantly across the cross-section, often appearing as shovel-like faults with a steeper upper portion and a gentler lower portion, whether the surface strike can be used to define the deep strike (and thus confirm the fault extension) is a question worth discussing. This requires support from high-resolution geophysical data. The reviewer emphasized that the paper needs to supplement the paper with deep geophysical data perpendicular to the fault strike in the Tehran region or adjacent areas (including citing other research results) to confirm the rationality of the coupling interpretation of the proposed tectonic model (Fig.13).
3. Since the superficial structural deformation mentioned in Q2 above is only a "result" of focal activity, it is not itself the cause of the earthquake. Therefore, if the model presented in the paper locates the earthquake source at a distance, the micro-epicenter will have deviated from the Tehran tectonic zone. The precise location of the minor earthquake currently presented does not demonstrate the validity of the model presented in this paper. Therefore, when revising the paper, the authors should carefully consider the universality of the regional tectonic model mentioned in Q1 and Q2 for local sections of the fault, and should not infer the overall tectonic characteristics from local sections.
4. Regarding the uncertainty in the magnitude determination of historical strong earthquakes, recent studies of moderate-to-strong earthquakes with instrumental records and comprehensive damage investigations (see studies in Italy, China, Japan, the United States, etc.) have shown that damage near the epicenter of moderate earthquakes can also be severe. Therefore, the magnitudes of historical strong earthquakes calculated based on only a small amount of literature may generally be overstated (Ou et al., 2020, JGR: SE). Therefore, the estimated magnitudes of historical earthquakes cannot be equated with instrumentally recorded magnitudes, leading to discussions of regional substantial earthquake hazard without supporting seismic tectonic context.
5. Other minor issues: a) The paper lacks a summary of the regional tectonic context; this should be supplemented; b) Figure 1a in the paper lacks key place names; c) The field photos in the figure should be positioned on the map; they are currently incomplete; d) The discussion of historical earthquakes in the Discussion section is insufficiently detailed; a figure should be added; e) The rationale for the tectonic model in the Discussion section requires further discussion; f) The paper could supplement the regional tectonic model with a figure (which can be cited); g) some oral sentences should be deleted, for example: line 21: According to our analyses, line 55 According to our findings, line360 As explained under Section 2.