Sedimentary record of historic seismicity in a small, southern Oregon lake

Morey, Ann Elizabeth; Shapley, Mark D.; Gavin, Daniel G.; Nelson, Alan R.; Goldfinger, Chris

doi:https://doi.org/10.21203/rs.3.rs-1631354/v2

Preprints

https://doi.org/10.21203/rs.3.rs-1631354/v2

Preprints

24 Aug 2023

| 24 Aug 2023

Sedimentary record of historic seismicity in a small, southern Oregon lake

Ann Elizabeth Morey, Mark D. Shapley, Daniel G. Gavin, Alan R. Nelson, and Chris Goldfinger

Abstract. We compare disturbances from the historic portion of the sedimentary record from Lower Squaw Lake, Oregon, to the historic record of events from the region to (1) determine if the lake records Cascadia megathrust earthquakes, and (2) if sediment deposits can be differentiated by disturbance type. We use the sedimentological characteristics and geochemically inferred provenance of the deposits (labelled A–J) from the historic portion (post 1650 CE) of the record to discriminate between types of deposits. We show that earthquake-triggered deposits are complex and flood deposits are simpler but vary depending on flood characteristics. Disturbance deposit J dates close to 1700 CE (1680–1780 CE) through multiple approaches. This deposit suspected to result from the magnitude (M) 8.8–9.2 1700 CE Cascadia megathrust earthquake is composed of unusually well-sorted, normally graded, medium-grained silt derived from distal rocks in the upper watershed. The silt grades upward, increasing in organic content forming a long, organic-rich tail. Load structures of silt into the organic-rich sediment below suggest rapid deposition. In contrast, a deposit attributed to the ~M7.0 1873 CE intraplate earthquake is a normally graded, medium-grained, watershed-sourced silt overlain by an organic tail and preceded by a lake-wide deposit interpreted as a wall failure from an earthquake that caused the landslide dam to fail. These results suggest that inland lakes can be sensitive recorders of earthquakes, and that it is possible to discriminate between plate margin and other types of earthquakes, and floods.

Received: 02 Jun 2023 – Discussion started: 24 Aug 2023

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Journal article(s) based on this preprint

11 Dec 2024

Sedimentary record of historical seismicity in a small, southern Oregon lake

Ann E. Morey, Mark D. Shapley, Daniel G. Gavin, Alan R. Nelson, and Chris Goldfinger

Nat. Hazards Earth Syst. Sci., 24, 4523–4561, https://doi.org/10.5194/nhess-24-4523-2024,https://doi.org/10.5194/nhess-24-4523-2024, 2024

Short summary

Ann Elizabeth Morey, Mark D. Shapley, Daniel G. Gavin, Alan R. Nelson, and Chris Goldfinger

Interactive discussion

Status: closed

CC1: 'Comment on egusphere-2023-1165', Shmuel Marco, 27 Sep 2023

Publisher’s note: this comment is a copy of RC1 and its content was therefore removed.

Citation: https://doi.org/10.5194/egusphere-2023-1165-CC1
RC1:
'Comment on egusphere-2023-1165', Shmuel Marco, 06 Oct 2023
Sorting out the various causes for changes in the sediment character is challenging in light of the multiple possible triggering processes, both natural and man-made.
The authors use numerous analytical methods for characterizing the layers suspected as seismites generated by a particular earthquake. The discussion on the depositional processes and how they were resolved is somewhat tedious and hard to follow, but I cannot suggest an improvement. The information is indeed relevant to the conclusions, so I suppose it better remain as is. The elaborate discussion is crucial because the radiocarbon dates cannot bracket the events tightly enough. Therefore, I value the submission as an example for applying multiple considerations in order to reach the best fit solution to a complex geological situation.
My main criticism is that the authors consider only mass transport deposits and do not ignore the option of sediment-water interaction during seismic shaking. This was shown to be significant in many previous works, in particular the ones related to the paleo Dead Sea seismites (e.g., Wetzler et al., 2010). Previous research also addressed the difference between earthquake-triggered in-situ deformation of lake bottom sediments and slope-originated mass transport deposits. However, this extensive body of works (e.g., Lu et al., 2017, 2020) is unfortunately ignored here.
Minor comments:
The authors conclude that their results “suggest that inland lakes can be sensitive recorders of earthquakes”. This is old news since evidence that inland lakes can be sensitive recorders of earthquakes has been around for over three decades. It is not a new revelation of this research.
Line 27: Earlier, much longer earthquake records (220 ka) have been reported from the Dead Sea Basin, where seismites are directly linked to synsedimentary faults and historical accounts of earthquakes (Lu et al., 2020 and references therein).
406: Flood deposits usually sink to the bottom within hours, even in saline lakes, where the debris/brine density contrast is smaller than in fresh water.

L 585: “steep” is too vague, please provide a measure of the slope. Slope failures can occur on less the 1°.
References
Lu, Y., Moernaut, J., Bookman, R., Waldmann, N., Wetzler, N., Agnon, A., Marco, S., Alsop, G.I., Strasser, M., and Hubert-Ferrari, A., 2021, A New Approach to Constrain the Seismic Origin for Prehistoric Turbidites as Applied to the Dead Sea Basin: Geophysical Research Letters, v. 48, doi:10.1029/2020GL090947.
Lu, Y., Waldmann, N., Ian Alsop, G., and Marco, S., 2017, Interpreting Soft Sediment Deformation and Mass Transport Deposits as Seismites in the Dead Sea Depocenter: Journal of Geophysical Research: Solid Earth, v. 122, p. 8305–8325, doi:10.1002/2017JB014342.
Lu, Y., Wetzler, N., Waldmann, N., Agnon, A., Biasi, G.P., and Marco, S., 2020, A 220,000-year-long continuous large earthquake record on a slow-slipping plate boundary: Science Advances, v. 6, p. eaba4170, doi:10.1126/sciadv.aba4170.
Wetzler, N., Marco, S., and Heifetz, E., 2010, Quantitative analysis of seismogenic shear-induced turbulence in lake sediments: Geology, v. 38, p. 303–306, doi:10.1130/G30685.1.
Citation: https://doi.org/10.5194/egusphere-2023-1165-RC1
- AC1: 'Comment on egusphere-2023-1165', Ann Morey, 05 Oct 2023
  
  Thank you, Shmuel, for the helpful comments. Please see responses below:
  "My main criticism is that the authors consider only mass transport deposits and do not ignore the option of sediment-water interaction during seismic shaking. This was shown to be significant in many previous works, in particular the ones related to the paleo Dead Sea seismites (e.g., Wetzler et al., 2010). Previous research also addressed the difference between earthquake-triggered in-situ deformation of lake bottom sediments and slope-originated mass transport deposits. However, this extensive body of works (e.g., Lu et al., 2017, 2020) is unfortunately ignored here."
  RESPONSE: Thank you for bringing to our attention the articles on Dead Sea seismites. These should have been referenced in the introduction. Note that although there are seismites present in the downcore record, the upper portion of the record does not have any obvious seismites. There are load structures that are the result of rapid settling of silt through the water column, but these are likely not the result of in-situ deformation of lake bottom sediments. We should make our reasoning clearer in the manuscript. Also, the deposits that produce the load structures are interpreted to be the result of injection, then settling, of silt into the water column . . . and therefore are not mass transport deposits.
  "The authors conclude that their results “suggest that inland lakes can be sensitive recorders of earthquakes”. This is old news since evidence that inland lakes can be sensitive recorders of earthquakes has been around for over three decades. It is not a new revelation of this research."
  RESPONSE: This comment refers to inland lakes in Cascadia. Cascadia was inadvertently omitted.
  
  Citation: https://doi.org/10.5194/egusphere-2023-1165-AC1
- AC2:
  'Reply on RC1', Ann Morey, 06 Oct 2023
  
  Thank you for the comment about flood deposits, Shmuel. I would love a reference for that statement if you know of one. Ann
  
  Citation: https://doi.org/10.5194/egusphere-2023-1165-AC2
  - RC2: 'Reply on AC2', Shmuel Marco, 06 Oct 2023
    
    Nehorai, R., I. M. Lensky, L. Hochman, I. Gertman, S. Brenner, A. Muskin, and N. G. Lensky (2013), Satellite observationsof turbidity in the Dead Sea,J. Geophys. Res. Oceans,118, 3146–3160, doi:10.1002/jgrc.20204
    
    Dear Ann, the relevant paragraph is at the bottom right on page 3155. I saw many flood events, usually on the following day almost all visible signs in the lake itself are gone.
    
    Citation: https://doi.org/10.5194/egusphere-2023-1165-RC2
    
    AC3: 'Reply on RC2', Ann Morey, 07 Oct 2023
    
    Thank you for the reference, Shmuel!
    
    Citation: https://doi.org/10.5194/egusphere-2023-1165-AC3
RC3:
'Comment on egusphere-2023-1165', Maarten Van Daele, 15 Dec 2023

It is clear that a lot of work and methods have gone into this impressive dataset and it contains a promising record. However, I do have concerns with some of the interpretations in the discussion, which can be summarized as: the authors invoke many poorly constrained mechanisms (e.g., lake level lowering, fine particles leaking out of a delta) and events (e.g. additional earthquakes in the historical part of the earthquake) too explain observations that can be more easily explained by widely recognized processes such as a delta failure. Also, some 137Cs dates would be really helpful to pinpoint the 1963/64 depth. My main comments are below and small comments are added to an annotated pdf that is attached.
There are (too) many figures in the manuscript. Please consider to move some to supplement.
Methods. Ideally you present the XRF data as centered-log-ratio (CLR) transformed to reduce the closed sum effect. See Weltje et al. (2015), or application in Schwestermann et al. (2020). This is nowadays routinely done for XRF scanning data.
Discussion.
Deposit J. The tail related to deposit J was initially not included to the event deposit, event though from Fig. 14 it is pretty clear that there is a tail (Bouma Te division) that is indeed not included in the deposit. This tail should, however, be included already in the results, so that it can also be taken into account for the age model. Furthermore, I am far from convinced that the silt deposit below J is part of the same event. We know from comparison with well-described events (e.g., Van Daele et al., 2017; Wils et al., 2021) that a long muddy tail means a significant time lag of at least days to weeks.
What about the deposit around 40 cm in SQB5 (Fig. 14), this also seems like an event deposit with a tail reaching until the base of event I.
Deposits G, H, I. I have sincere problems with the proposed interpretations. A lot of new mechanisms are invented (e.g. line 550-555 and section 4.3.3), while there are plenty known mechanisms (rock avalanche, delta failure...) that can much easier explain the observed deposits.
- I: do the authors interpret this as sourced from terrestrial or subaquatic slopes? If subaquatic, why did the 1700 CE earthquake not trigger any (!!!) failures on these slopes? Hence, I suggest the authors clarify in the text that this must be the terrestrial slopes.
The summary further includes a dam collapse and lake lowering for which no further evidence is provided. I have the feeling that a lot of additional mechanisms are invoked for which there is no evidence. In my opinion the authors make the story more complicated then it needs to be.
- H: in my opinion the authors give too much credit to core SBQ9. This is the only core where multiple pulses are observed. Why is the option that it is in fact an amalgamated turbidite considered unlikely? This core is in the depocenter (this is indeed the location where this could be expected), and apart form this core, only in SQB13 and SQB10 there is perhaps some evidence of such amalgamation, which is indeed also in the depocenter and away from the main (deltaic) sources, where also flow partitioning could get more influence. Furthermore, also event deposit J seems to have 2 pulses in exactly these cores, (and event G!) indicating that the presence of multiple "pulses" seems to be related to these locations, rather then to the specific event(s). Also, how do the authors explain these additional earthquakes, while they have not been historically reported?
- G: as reverse grading is observed, could this be a catchment response ("flood") related to events H and I? The authors link it to a documented dam failure, in that case the deposit should be coarser and thicker towards the dam (e.g. 1929 dam collapse in Eklutna Lake; Boes et al., 2018), is this the case?
An alternative interpretation of this sequence would be something similar to what's discussed in Van Daele et al. (2019) (this is anyway a pretty important reference in this paper, as it also deals with the sedimentary imprint of megathrust and intraslab earthquakes and how to distinguish them). As the 1873 earthquake was an intraslab earthquake, the high-frequency content of the shaking could have cause onshore landslides (in contrast to 1700, which would've caused more voluminous deltaic failures due to the longer duration of low frequency shaking). Hence, initially onshore landslides in the schist along the lake could have traveled directly into the lake (event deposit I). The shaking would've also cause delta failures (albeit small ones), which arrive slightly later to the core locations (event deposit H). Finally, onshore landslide in the catchment would've been transported to the lake in the years following the earthquake (event deposit G). UNLESS there is actually background sediment between event deposits I and H...?
Events C-A: Some 137Cs dates seem to be indispensable to locate the 1963/64 atomic bomb peak and thus confidently attribute the corect deposit to the 1964 floods, and probably also to the 1955 floods.
Fig. 23: the ratio is probably organic/inorganic, unlike what is mentioned in the caption. This data should be plotted in the same style as all other figures, and both with the same software.
References:
Boes, E., Van Daele, M., Moernaut, J., Schmidt, S., Jensen, B. J. L., Praet, N., Kaufman, D., Haeussler, P., Loso, M. G. and De Batist, M. (2018). "Varve formation during the past three centuries in three large proglacial lakes in south-central Alaska." GSA Bulletin 130(5-6): 757-774.

Schwestermann, T., Huang, J., Konzett, J., Kioka, A., Wefer, G., Ikehara, K., Moernaut, J., Eglinton, T.I., Strasser, M., 2020. Multivariate Statistical and Multiproxy Constraints on Earthquake-Triggered Sediment Remobilization Processes in the Central Japan Trench. Geochemistry, Geophysics, Geosystems 21, 1–24. https://doi.org/10.1029/2019GC008861
Van Daele, M., Moernaut, J., Doom, L., Boes, E., Fontijn, K., Heirman, K., Vandoorne, W., Hebbeln, D., Pino, M., Urrutia, R., Brümmer, R. and De Batist, M. (2015). "A comparison of the sedimentary records of the 1960 and 2010 great Chilean earthquakes in 17 lakes: Implications for quantitative lacustrine palaeoseismology." Sedimentology 62(5): 1466-1496.

Van Daele, M., Meyer, I., Moernaut, J., De Decker, S., Verschuren, D. and De Batist, M. (2017). "A revised classification and terminology for stacked and amalgamated turbidites in environments dominated by (hemi) pelagic sedimentation." Sedimentary Geology 357: 72-82.

Van Daele, M., Araya-Cornejo, C., Pille, T., Vanneste, K., Moernaut, J., Schmidt, S., Kempf, P., Meyer, I. and Cisternas, M. (2019). "Distinguishing intraplate from megathrust earthquakes using lacustrine turbidites." Geology 47: 127-130.

Weltje, G.J., Bloemsma, M.R., Tjallingii, R., Heslop, D., Röhl, U., Croudace, Ian W., 2015. Prediction of Geochemical Composition from XRF Core Scanner Data: A New Multivariate Approach Including Automatic Selection of Calibration Samples and Quantification of Uncertainties, in: Croudace, I.W., Rothwell, R.G. (Eds.), Micro-XRF Studies of Sediment Cores. Springer Dordrecht, pp. 507–534. https://doi.org/10.1007/978-94-017-9849-5_21

Wils, K., Deprez, M., Kissel, C., Vervoort, M., Van Daele, M., Daryono, M. R., Cnudde, V., Natawidjaja, D. H. and De Batist, M. (2021). "Earthquake doublet revealed by multiple pulses in lacustrine seismo-turbidites." Geology 49(11): 1301-1306.

Maarten Van Daele

Citation: https://doi.org/10.5194/egusphere-2023-1165-RC3
- AC4:
  'Reply on RC3', Ann Morey, 23 Jan 2024
  
  Thank you, Maarten, for your valuable comments. Please see the supplement for detailed author responses (attached).
  Ann
  
  Citation: https://doi.org/10.5194/egusphere-2023-1165-AC4
  - AC5: 'Reply on AC4', Ann Morey, 24 Jan 2024
    
    I would like to make a correction to my response to one of Maarten Van Daele's comments. Please see the attached pdf.
    
    Citation: https://doi.org/10.5194/egusphere-2023-1165-AC5

Interactive discussion

Status: closed

CC1: 'Comment on egusphere-2023-1165', Shmuel Marco, 27 Sep 2023

Publisher’s note: this comment is a copy of RC1 and its content was therefore removed.

Citation: https://doi.org/10.5194/egusphere-2023-1165-CC1
RC1:
'Comment on egusphere-2023-1165', Shmuel Marco, 06 Oct 2023
Sorting out the various causes for changes in the sediment character is challenging in light of the multiple possible triggering processes, both natural and man-made.
The authors use numerous analytical methods for characterizing the layers suspected as seismites generated by a particular earthquake. The discussion on the depositional processes and how they were resolved is somewhat tedious and hard to follow, but I cannot suggest an improvement. The information is indeed relevant to the conclusions, so I suppose it better remain as is. The elaborate discussion is crucial because the radiocarbon dates cannot bracket the events tightly enough. Therefore, I value the submission as an example for applying multiple considerations in order to reach the best fit solution to a complex geological situation.
My main criticism is that the authors consider only mass transport deposits and do not ignore the option of sediment-water interaction during seismic shaking. This was shown to be significant in many previous works, in particular the ones related to the paleo Dead Sea seismites (e.g., Wetzler et al., 2010). Previous research also addressed the difference between earthquake-triggered in-situ deformation of lake bottom sediments and slope-originated mass transport deposits. However, this extensive body of works (e.g., Lu et al., 2017, 2020) is unfortunately ignored here.
Minor comments:
The authors conclude that their results “suggest that inland lakes can be sensitive recorders of earthquakes”. This is old news since evidence that inland lakes can be sensitive recorders of earthquakes has been around for over three decades. It is not a new revelation of this research.
Line 27: Earlier, much longer earthquake records (220 ka) have been reported from the Dead Sea Basin, where seismites are directly linked to synsedimentary faults and historical accounts of earthquakes (Lu et al., 2020 and references therein).
406: Flood deposits usually sink to the bottom within hours, even in saline lakes, where the debris/brine density contrast is smaller than in fresh water.

L 585: “steep” is too vague, please provide a measure of the slope. Slope failures can occur on less the 1°.
References
Lu, Y., Moernaut, J., Bookman, R., Waldmann, N., Wetzler, N., Agnon, A., Marco, S., Alsop, G.I., Strasser, M., and Hubert-Ferrari, A., 2021, A New Approach to Constrain the Seismic Origin for Prehistoric Turbidites as Applied to the Dead Sea Basin: Geophysical Research Letters, v. 48, doi:10.1029/2020GL090947.
Lu, Y., Waldmann, N., Ian Alsop, G., and Marco, S., 2017, Interpreting Soft Sediment Deformation and Mass Transport Deposits as Seismites in the Dead Sea Depocenter: Journal of Geophysical Research: Solid Earth, v. 122, p. 8305–8325, doi:10.1002/2017JB014342.
Lu, Y., Wetzler, N., Waldmann, N., Agnon, A., Biasi, G.P., and Marco, S., 2020, A 220,000-year-long continuous large earthquake record on a slow-slipping plate boundary: Science Advances, v. 6, p. eaba4170, doi:10.1126/sciadv.aba4170.
Wetzler, N., Marco, S., and Heifetz, E., 2010, Quantitative analysis of seismogenic shear-induced turbulence in lake sediments: Geology, v. 38, p. 303–306, doi:10.1130/G30685.1.
Citation: https://doi.org/10.5194/egusphere-2023-1165-RC1
- AC1: 'Comment on egusphere-2023-1165', Ann Morey, 05 Oct 2023
  
  Thank you, Shmuel, for the helpful comments. Please see responses below:
  "My main criticism is that the authors consider only mass transport deposits and do not ignore the option of sediment-water interaction during seismic shaking. This was shown to be significant in many previous works, in particular the ones related to the paleo Dead Sea seismites (e.g., Wetzler et al., 2010). Previous research also addressed the difference between earthquake-triggered in-situ deformation of lake bottom sediments and slope-originated mass transport deposits. However, this extensive body of works (e.g., Lu et al., 2017, 2020) is unfortunately ignored here."
  RESPONSE: Thank you for bringing to our attention the articles on Dead Sea seismites. These should have been referenced in the introduction. Note that although there are seismites present in the downcore record, the upper portion of the record does not have any obvious seismites. There are load structures that are the result of rapid settling of silt through the water column, but these are likely not the result of in-situ deformation of lake bottom sediments. We should make our reasoning clearer in the manuscript. Also, the deposits that produce the load structures are interpreted to be the result of injection, then settling, of silt into the water column . . . and therefore are not mass transport deposits.
  "The authors conclude that their results “suggest that inland lakes can be sensitive recorders of earthquakes”. This is old news since evidence that inland lakes can be sensitive recorders of earthquakes has been around for over three decades. It is not a new revelation of this research."
  RESPONSE: This comment refers to inland lakes in Cascadia. Cascadia was inadvertently omitted.
  
  Citation: https://doi.org/10.5194/egusphere-2023-1165-AC1
- AC2:
  'Reply on RC1', Ann Morey, 06 Oct 2023
  
  Thank you for the comment about flood deposits, Shmuel. I would love a reference for that statement if you know of one. Ann
  
  Citation: https://doi.org/10.5194/egusphere-2023-1165-AC2
  - RC2: 'Reply on AC2', Shmuel Marco, 06 Oct 2023
    
    Nehorai, R., I. M. Lensky, L. Hochman, I. Gertman, S. Brenner, A. Muskin, and N. G. Lensky (2013), Satellite observationsof turbidity in the Dead Sea,J. Geophys. Res. Oceans,118, 3146–3160, doi:10.1002/jgrc.20204
    
    Dear Ann, the relevant paragraph is at the bottom right on page 3155. I saw many flood events, usually on the following day almost all visible signs in the lake itself are gone.
    
    Citation: https://doi.org/10.5194/egusphere-2023-1165-RC2
    
    AC3: 'Reply on RC2', Ann Morey, 07 Oct 2023
    
    Thank you for the reference, Shmuel!
    
    Citation: https://doi.org/10.5194/egusphere-2023-1165-AC3
RC3:
'Comment on egusphere-2023-1165', Maarten Van Daele, 15 Dec 2023

It is clear that a lot of work and methods have gone into this impressive dataset and it contains a promising record. However, I do have concerns with some of the interpretations in the discussion, which can be summarized as: the authors invoke many poorly constrained mechanisms (e.g., lake level lowering, fine particles leaking out of a delta) and events (e.g. additional earthquakes in the historical part of the earthquake) too explain observations that can be more easily explained by widely recognized processes such as a delta failure. Also, some 137Cs dates would be really helpful to pinpoint the 1963/64 depth. My main comments are below and small comments are added to an annotated pdf that is attached.
There are (too) many figures in the manuscript. Please consider to move some to supplement.
Methods. Ideally you present the XRF data as centered-log-ratio (CLR) transformed to reduce the closed sum effect. See Weltje et al. (2015), or application in Schwestermann et al. (2020). This is nowadays routinely done for XRF scanning data.
Discussion.
Deposit J. The tail related to deposit J was initially not included to the event deposit, event though from Fig. 14 it is pretty clear that there is a tail (Bouma Te division) that is indeed not included in the deposit. This tail should, however, be included already in the results, so that it can also be taken into account for the age model. Furthermore, I am far from convinced that the silt deposit below J is part of the same event. We know from comparison with well-described events (e.g., Van Daele et al., 2017; Wils et al., 2021) that a long muddy tail means a significant time lag of at least days to weeks.
What about the deposit around 40 cm in SQB5 (Fig. 14), this also seems like an event deposit with a tail reaching until the base of event I.
Deposits G, H, I. I have sincere problems with the proposed interpretations. A lot of new mechanisms are invented (e.g. line 550-555 and section 4.3.3), while there are plenty known mechanisms (rock avalanche, delta failure...) that can much easier explain the observed deposits.
- I: do the authors interpret this as sourced from terrestrial or subaquatic slopes? If subaquatic, why did the 1700 CE earthquake not trigger any (!!!) failures on these slopes? Hence, I suggest the authors clarify in the text that this must be the terrestrial slopes.
The summary further includes a dam collapse and lake lowering for which no further evidence is provided. I have the feeling that a lot of additional mechanisms are invoked for which there is no evidence. In my opinion the authors make the story more complicated then it needs to be.
- H: in my opinion the authors give too much credit to core SBQ9. This is the only core where multiple pulses are observed. Why is the option that it is in fact an amalgamated turbidite considered unlikely? This core is in the depocenter (this is indeed the location where this could be expected), and apart form this core, only in SQB13 and SQB10 there is perhaps some evidence of such amalgamation, which is indeed also in the depocenter and away from the main (deltaic) sources, where also flow partitioning could get more influence. Furthermore, also event deposit J seems to have 2 pulses in exactly these cores, (and event G!) indicating that the presence of multiple "pulses" seems to be related to these locations, rather then to the specific event(s). Also, how do the authors explain these additional earthquakes, while they have not been historically reported?
- G: as reverse grading is observed, could this be a catchment response ("flood") related to events H and I? The authors link it to a documented dam failure, in that case the deposit should be coarser and thicker towards the dam (e.g. 1929 dam collapse in Eklutna Lake; Boes et al., 2018), is this the case?
An alternative interpretation of this sequence would be something similar to what's discussed in Van Daele et al. (2019) (this is anyway a pretty important reference in this paper, as it also deals with the sedimentary imprint of megathrust and intraslab earthquakes and how to distinguish them). As the 1873 earthquake was an intraslab earthquake, the high-frequency content of the shaking could have cause onshore landslides (in contrast to 1700, which would've caused more voluminous deltaic failures due to the longer duration of low frequency shaking). Hence, initially onshore landslides in the schist along the lake could have traveled directly into the lake (event deposit I). The shaking would've also cause delta failures (albeit small ones), which arrive slightly later to the core locations (event deposit H). Finally, onshore landslide in the catchment would've been transported to the lake in the years following the earthquake (event deposit G). UNLESS there is actually background sediment between event deposits I and H...?
Events C-A: Some 137Cs dates seem to be indispensable to locate the 1963/64 atomic bomb peak and thus confidently attribute the corect deposit to the 1964 floods, and probably also to the 1955 floods.
Fig. 23: the ratio is probably organic/inorganic, unlike what is mentioned in the caption. This data should be plotted in the same style as all other figures, and both with the same software.
References:
Boes, E., Van Daele, M., Moernaut, J., Schmidt, S., Jensen, B. J. L., Praet, N., Kaufman, D., Haeussler, P., Loso, M. G. and De Batist, M. (2018). "Varve formation during the past three centuries in three large proglacial lakes in south-central Alaska." GSA Bulletin 130(5-6): 757-774.

Schwestermann, T., Huang, J., Konzett, J., Kioka, A., Wefer, G., Ikehara, K., Moernaut, J., Eglinton, T.I., Strasser, M., 2020. Multivariate Statistical and Multiproxy Constraints on Earthquake-Triggered Sediment Remobilization Processes in the Central Japan Trench. Geochemistry, Geophysics, Geosystems 21, 1–24. https://doi.org/10.1029/2019GC008861
Van Daele, M., Moernaut, J., Doom, L., Boes, E., Fontijn, K., Heirman, K., Vandoorne, W., Hebbeln, D., Pino, M., Urrutia, R., Brümmer, R. and De Batist, M. (2015). "A comparison of the sedimentary records of the 1960 and 2010 great Chilean earthquakes in 17 lakes: Implications for quantitative lacustrine palaeoseismology." Sedimentology 62(5): 1466-1496.

Van Daele, M., Meyer, I., Moernaut, J., De Decker, S., Verschuren, D. and De Batist, M. (2017). "A revised classification and terminology for stacked and amalgamated turbidites in environments dominated by (hemi) pelagic sedimentation." Sedimentary Geology 357: 72-82.

Van Daele, M., Araya-Cornejo, C., Pille, T., Vanneste, K., Moernaut, J., Schmidt, S., Kempf, P., Meyer, I. and Cisternas, M. (2019). "Distinguishing intraplate from megathrust earthquakes using lacustrine turbidites." Geology 47: 127-130.

Weltje, G.J., Bloemsma, M.R., Tjallingii, R., Heslop, D., Röhl, U., Croudace, Ian W., 2015. Prediction of Geochemical Composition from XRF Core Scanner Data: A New Multivariate Approach Including Automatic Selection of Calibration Samples and Quantification of Uncertainties, in: Croudace, I.W., Rothwell, R.G. (Eds.), Micro-XRF Studies of Sediment Cores. Springer Dordrecht, pp. 507–534. https://doi.org/10.1007/978-94-017-9849-5_21

Wils, K., Deprez, M., Kissel, C., Vervoort, M., Van Daele, M., Daryono, M. R., Cnudde, V., Natawidjaja, D. H. and De Batist, M. (2021). "Earthquake doublet revealed by multiple pulses in lacustrine seismo-turbidites." Geology 49(11): 1301-1306.

Maarten Van Daele

Citation: https://doi.org/10.5194/egusphere-2023-1165-RC3
- AC4:
  'Reply on RC3', Ann Morey, 23 Jan 2024
  
  Thank you, Maarten, for your valuable comments. Please see the supplement for detailed author responses (attached).
  Ann
  
  Citation: https://doi.org/10.5194/egusphere-2023-1165-AC4
  - AC5: 'Reply on AC4', Ann Morey, 24 Jan 2024
    
    I would like to make a correction to my response to one of Maarten Van Daele's comments. Please see the attached pdf.
    
    Citation: https://doi.org/10.5194/egusphere-2023-1165-AC5

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

ED: Reconsider after major revisions (further review by editor and referees) (24 Jan 2024) by Oded Katz

AR by Ann Morey on behalf of the Authors (21 Mar 2024)

EF by Polina Shvedko (19 Apr 2024) Author's response

EF by Sarah Buchmann (17 May 2024) Supplement

EF by Sarah Buchmann (21 May 2024) Manuscript Author's tracked changes

ED: Referee Nomination & Report Request started (21 May 2024) by Oded Katz

RR by Anonymous Referee #3 (03 Jun 2024)

Suggestions for revision or reasons for rejection

The authors develop an original technique of evaluating the XRF data of the event deposits in scatter plots and look for distinct patterns that help understanding the depositional processes and source regions of the event deposits. This scatter-plot technique is commonly applied for grain size data on event deposits, but using this approach on XRF data is a first time and bears a great potential in other studies as well. The authors make an extensive argumentation that they use the raw XRF data and not the log-ratio transformation of the data (a transformation suggested by the reviewer and which is common practice in sediment geochemistry. As raw counts is not geochemistry data, but rather a mixture of density, grain size and element abundance, interpretation is becoming more difficult. I suggest the authors to re-consider the usage of the CLR approach. Using the Centre-log-ratio (CLR) is important to decrease the effect of grain-size and density and get geochemical robust data from XRF scans. The authors mention that the CLR approach can produce more “noise”, which is true. Therefore, it is crucial to select only elements with high signal-to-noise ratio for the calculation of the geometric mean, and to remove any 0 or negative values. So, I suggest the authors to re-consider the usage of the CLR approach on a selected suite of high-quality elements and evaluate the quality of the results. Of course, the final decision is up to the authors on what they consider the most meaningful.

In any case (raw counts or CLR transformed data), the data presented in Fig. 19 B (K/Si x Density) and interpretation is not acceptable to me. I do not understand the scientific meaning of this procedure. If radiodensity is inherently part of the raw XRF counts, I suppose you just increase this effect by multiplying XRF data with CT density? The resulting quantity is in HU, what would be the physical meaning of this value? Please elaborate it properly and make this more convincing in the article, or alternatively, delete this part.

For the loops in the XRF scatter plots: the authors rely on the assumption that the background sediment before and after the event is exactly the same, and based on this try to identify the base and top of the event deposit (see event J: Fig. 20). This assumes that earthquakes do not produce any long-term catchment response and no other paleo-environmental changes (human influences in the catchment, climate changes, etc) occurred in the specific timeframes as this would lead to background sediments with different values. This assumption should be evaluated and clearly stated in the manuscript.

I agree with one of the previous reviewers that the authors invoke several new mechanisms (which have not been documented elsewhere) to explain observations that can be more easily explained by widely recognized processes (e.g. delta failure). I am not going to summarize these (this was done by the previous reviewer). This extra process complexity is not necessary in my opinion, but accept it to be the choice of the authors to put forward these ideas and hypotheses. What matters most for good science is to present robust data in the best way possible, whereas interpretations may change over time. The authors discuss their interpretations in an extensive way, which is required to for the readership to follow the logic argumentation.

Several figures need to be improved (see list below).

Overall, I recommend moderate revisions.

Detailed comments:

Abstract:
I suggest to write “Cascadia megathrust earthquakes”, not just “Cascadia earthquakes”.

Methods: you write that mineralogy was spot-checked using the CSD desktop scanning electron microscope. Where do you show data for this? Also, in the results you mention: “Inspection by Energy-dispersive x-ray spectroscopy (Bruker Quantax 50 EDS; CSD Facility) showed that some mica flakes from the Condrey Mountain Schist surrounding the lake contain a large amount of carbon (as much as 77%) and scanning-electron-microscopic analysis shows the presence of pyrite.” You do not show that data. Please add this data to the supplement.

Discussion:
L404: please update “Only one study (Van Daele et al., 2019) has successfully discriminated between intraplate and megathrust earthquakes using lake sediments.” See e.g. Praet et al., 2022 https://onlinelibrary.wiley.com/doi/abs/10.1111/sed.12986
L405-410: this explanation is partly correct. The intraslab events in that study also produce thin coseismic turbidites in that lake, AND are followed by catchment response.
L465: I suggest to also refer to the review paper of Bertrand et al., 2024 which is discussing all these issues. https://www.sciencedirect.com/science/article/pii/S0012825223003288
L472: “When scaled by radiodensity (Figure 19b),” I do not understand the scientific meaning of this calculation. If radiodensity is inherently part of the raw XRF counts, I suppose you just increase this effect by multiplying XRF data with CT density. What would be the purpose of this? Please elaborate and make this more convincing in the article, or alternatively, delete this part.
L619: Is SQB5 really located on a ~45° slope? I would not expect any sediment accumulation on slopes steeper than 25°, so that seems strange. Please verify the slope angle calculation you did.

To me, the “summary of interpretations” and “conclusions” contain to much repetition. I suggest to keep the conclusions short and focus on the implications of your study rather than explaining the nature of each event deposit again.

Clearness and structure of the figures (also in the supplement):

In general, I think that the figure captions are often too large. They should help the reader to understand the figure, but do should not go into the interpretation of the data. This is done in the main text of the article. I suggest to shorten the figure captions to avoid repetition. E.g. a discussion sentence “could this be the result of a post-subduction earthquake aftershock, another subduction earthquake, a large crustal or intraplate earthquake?” should not be in a figure caption (Fig. 20).

Labeling and units: many figures are missing key elements such as labels and units for the axes. Also, several cores and core plots (such as CT density) are missing a depth scale! (e.g. fig. 21).

Fig. 1: what are the blue lines? Are these the faults from the simplified Cascadia forearc fault model?
Fig. 3: How is this “spike” in conductivity obtained and why is it not part of the grey curve?
In which month is the data measured (important for the development of a thermocline)?
Fig. 4: many cores were taken on slopes, which can make the record more complicated. As seen in e.g. Molenaar et al.,2021 (https://onlinelibrary.wiley.com/doi/full/10.1111/sed.12856) a slope angle of a few degrees can be enough to have stratigraphic gaps caused by surficial remobilization (due to earthquakes) and to develop in-situ soft sediment deformation structures. It would be good for the reader to get information about the coring strategy.
Fig. 5: The legend shows many lithology symbols, but none of them are used in the figure.
Fig.5 and 6: It would be useful to indicate the top and bottom of each event deposit. In this way, it is much easier for the reader to see how the event deposits and the background sediments change throughout the lake basin.
Fig. 7: typo in legend “vivianiate”
Fig. 10: there is way too much text next to the smear slides
Fig. 11: At the bottom left there are some plots which are illegible.
Fig. 12: The age model is illegible
Fig. 18: A) Please provide an arrow so we see the direction of the “loops”
Also, why do you use the sequence number as X-axis in Fig. C? It would be easier for the audience if you just plot sediment depth. Same for Fig. 19
Fig. 19: The colors related to some event deposits have changed compared to Fig. 18. This makes comparison a tedious task. E.g. deposit I is purple (Fig. 18) or red (Fig. 19)…
Fig. 20: the legend states “confidence intervals in orange”. However, I do not see any orange in the plots.
Fig. 22 (and others): “Note that the horizontal axis for the cartoon of the deposit sequence (bottom right) represents sediment radiodensity.” Good that you mention this, but it should be mentioned for all figures that show such a cartoon (e.g. Fig. 10). Otherwise, any sedimentologist in this world would think that the horizontal axis in these cartoons represent grain size and not radiodensity.
Fig. 23: This caption needs more explanation: which deposit are you using as representative of “flood” and of “earthquake”? Also indicate the arrow on the XRF data loops.

Supplement:

2a: XRD figures: screenshots: data and scales are illegible.
2B: XRD data: the plot axes have no units. Also, the core has no depth scale.
3. I do not see any “red fault lines ”on the map. I guess you refer to the black lines? As these are based on tracing lineaments on topographic data, the map would be more convincing if it would include topography information (i.e. DEM of the region).
4. The table headers need units.

Hide

ED: Reconsider after major revisions (further review by editor and referees) (26 Jun 2024) by Oded Katz

AR by Ann Morey on behalf of the Authors (22 Aug 2024) Author's response

EF by Anna Glados (02 Sep 2024) Manuscript Author's tracked changes

ED: Publish as is (22 Sep 2024) by Oded Katz

AR by Ann Morey on behalf of the Authors (11 Oct 2024)

Journal article(s) based on this preprint

11 Dec 2024

Sedimentary record of historical seismicity in a small, southern Oregon lake

Ann E. Morey, Mark D. Shapley, Daniel G. Gavin, Alan R. Nelson, and Chris Goldfinger

Nat. Hazards Earth Syst. Sci., 24, 4523–4561, https://doi.org/10.5194/nhess-24-4523-2024,https://doi.org/10.5194/nhess-24-4523-2024, 2024

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Ann Elizabeth Morey, Mark D. Shapley, Daniel G. Gavin, Alan R. Nelson, and Chris Goldfinger

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Short summary

Disturbance events from historic sediments from a small lake in Oregon were compared to known events to determine if Cascadia earthquakes are uniquely identifiable. Sedimentological methods and geochemical provenance data identify a deposit likely from the most recent Cascadia earthquake (which occurred in 1700), another type of earthquake deposit, and flood deposits, suggesting that small lakes are good recorders of megathrust earthquakes. New methods developed hold promise for other lakes.


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