the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 14 Aug 2023
Prediction of Crustal Dynamics for the Yishu Fault Zone Based on Slip Susceptibility Analysis
Abstract. We estimate the slip susceptibility of faults in the Yishu fault zone using a slip tendency analysis based on coupled tectonic stress profiles. Studying in situ stress data and focal mechanism solution data collected in this area over more than 30 years, we construct the stress profiles of the study area using the coupling analysis method for deep and shallow stress data. Subsequently, the slip susceptibility of the faults is comprehensively evaluated based on various stress indicators and other related influencing factors. Our results show that μm is low in the deep and shallow crust of the Yishu fault zone, indicating a relatively low degree of overall stress accumulation. A comprehensive evaluation of the susceptibility of fault slips based on five typical influencing factors (μm, K, θ, S-wave velocity, and seismic density) indicates that the overall seismic risk in the central part of the Yishu fault zone is not high, while the northwestern Yishu fault zone exhibits high seismic risk. The southeastern part of the Yishu fault zone reflects the transition from medium to low seismic risk. These results provide geomechanical and fault mechanics evidence for evaluating the regional crustal dynamics of the Yishu fault zone.
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RC1: 'Comment on egusphere-2023-1567', Anonymous Referee #1, 07 Oct 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1567/egusphere-2023-1567-RC1-supplement.pdf
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RC2: 'Comment on egusphere-2023-1567', Anonymous Referee #2, 12 Nov 2023
Thank you for providing an opportunity to read a manuscript entitled “Prediction of Crustal Dynamics for the Yishu Fault Zone Based on Slip Susceptibility Analysis Guiyun” by Gao et al.
It may be interesting paper and giving important suggestions. However, there are points I cannot understand due to lack of description and/or data handling problem although there is a possibility of my misunderstand. In addition, I am not specialist for stress measurement in borehole. Therefore, I describe about part where they study stress in deep part. I list them as follows.
- A) Friction coefficient estimation
1) How can you estimate the coefficient over 700 from only 913 events?
To estimate it, distribution of P axis around maximum principal stress direction is required.
I think the coefficient can be estimated from statistical analysis for the distribution. If a bimodal distribution of P axis around the principal stress, it maybe estimated. However, distribution with one peak (like Gaussian) arises possibility that is attributed to estimation error in focal mechanism estimation, which is likely.
2) Under a stress condition, variation of P axis is attributed to either friction coefficient or pore fluid pressure. If the author put the cause on the friction coefficient, assumption of the pore fluid pressure is needed. How can be assumed? In addition, no description about stress field estimation in the discussion about friction coefficient. After stress estimation, fault plane selection for each focal mechanism is required. How can you fix it?
3) In addition, the author described earthquakes with types RF, SL, and NF occurred in the target region. Therefore, it is not reasonable to assume uniform state of stress.
4) How can you estimate errors of parameters?
- B) Absolute stress estimation
1) How can you estimate both kh and kH from only EQ 9) and R value?
Both values must different each stress regime because the values in EQ 9) are based on geometrical relationship between kh, kH, and 1 (Sv/Sv) in Mohr diagram and overburden pressure. For example SH > lithostatic pressure in strike slip and reverse fault regimes. On the other hand, SH< lithostatic one in normal fault regime. Then kH for RF, SS > KH for NF..
2) Under assumption Andersonean and Coulomb failure criteria, absolute value of stress can be obtained from friction coefficient, pore fluid pressure, stress ratio and depth. How are the values set? It is necessary to describe this point with reasonable basis.
3) Principal directions can be estimated from stress inversion using focal mechanism as well. It may show spatial variation in the target region as showing focal mechanism map. How was it? Principal directions and its error effect on the frictional coefficient estimation and absolute stress meaurement. How did you treat them?
Citation: https://doi.org/10.5194/egusphere-2023-1567-RC2
Status: closed
-
RC1: 'Comment on egusphere-2023-1567', Anonymous Referee #1, 07 Oct 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1567/egusphere-2023-1567-RC1-supplement.pdf
-
RC2: 'Comment on egusphere-2023-1567', Anonymous Referee #2, 12 Nov 2023
Thank you for providing an opportunity to read a manuscript entitled “Prediction of Crustal Dynamics for the Yishu Fault Zone Based on Slip Susceptibility Analysis Guiyun” by Gao et al.
It may be interesting paper and giving important suggestions. However, there are points I cannot understand due to lack of description and/or data handling problem although there is a possibility of my misunderstand. In addition, I am not specialist for stress measurement in borehole. Therefore, I describe about part where they study stress in deep part. I list them as follows.
- A) Friction coefficient estimation
1) How can you estimate the coefficient over 700 from only 913 events?
To estimate it, distribution of P axis around maximum principal stress direction is required.
I think the coefficient can be estimated from statistical analysis for the distribution. If a bimodal distribution of P axis around the principal stress, it maybe estimated. However, distribution with one peak (like Gaussian) arises possibility that is attributed to estimation error in focal mechanism estimation, which is likely.
2) Under a stress condition, variation of P axis is attributed to either friction coefficient or pore fluid pressure. If the author put the cause on the friction coefficient, assumption of the pore fluid pressure is needed. How can be assumed? In addition, no description about stress field estimation in the discussion about friction coefficient. After stress estimation, fault plane selection for each focal mechanism is required. How can you fix it?
3) In addition, the author described earthquakes with types RF, SL, and NF occurred in the target region. Therefore, it is not reasonable to assume uniform state of stress.
4) How can you estimate errors of parameters?
- B) Absolute stress estimation
1) How can you estimate both kh and kH from only EQ 9) and R value?
Both values must different each stress regime because the values in EQ 9) are based on geometrical relationship between kh, kH, and 1 (Sv/Sv) in Mohr diagram and overburden pressure. For example SH > lithostatic pressure in strike slip and reverse fault regimes. On the other hand, SH< lithostatic one in normal fault regime. Then kH for RF, SS > KH for NF..
2) Under assumption Andersonean and Coulomb failure criteria, absolute value of stress can be obtained from friction coefficient, pore fluid pressure, stress ratio and depth. How are the values set? It is necessary to describe this point with reasonable basis.
3) Principal directions can be estimated from stress inversion using focal mechanism as well. It may show spatial variation in the target region as showing focal mechanism map. How was it? Principal directions and its error effect on the frictional coefficient estimation and absolute stress meaurement. How did you treat them?
Citation: https://doi.org/10.5194/egusphere-2023-1567-RC2
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