Estimation of Co-Seismic Surface Deformation Induced by 24 September 2019 Mirpur, Pakistan Earthquake along an Active Blind Fault Using Sentinel-1 TOPS Interferometry

Round 1

Reviewer 1 Report

I found interesting the manuscript "Remote Sens. 2023, 15, x. https://doi.org/10.3390/xxxxx" submitted by Ali M. et al. The authors utilized Sentinel-1 SAR data to determine the surface deformation caused by an earthquake along an active blind fault. In 2019, a seismic event of 5.6 Mw and 10 km  depth took place in the vicinity of Mirpur, Pakistan. The objective of this study is to assess the extent of surface deformation caused by the earthquake in Mirpur and its surrounding regions. The application of the interferometric synthetic aperture radar technology is utilised for the investigation of surface motion caused by earthquakes. The study utilises InSAR data comprising 9 Sentinel-1A SAR pictures captured between 11 August 2019 and 22 October 2019 to examine potential changes in pre-, co-, and post-seismic deformation. The analysis of the time series data indicates that there was no statistically significant deformation seen during the pre-seismic period. Significant displacement was reported throughout the co-seismic period and in the subsequent post-seismic periods. The primary result of the study is the validation of the presence of a hitherto undocumented auditory impairment in Mirpur. The authors have shown that the study area is encountering numerous challenges as a result of natural hazards, specifically due to surface deformations caused by earthquakes with activated blind faults, which have heightened its susceptibility. I have appreciated the scientific robustness; nonetheless, it would be beneficial for the authors to provide more commentary on the findings and inquire about the relative ease of observing pre-seismic deformations in extensional versus compressional conditions. This approach would enhance the visibility of the innovation aspects.

Author Response

We thank the Reviewer for his comments providing an overview of the key contributions of the paper. As far as the Reviewer suggestion of providing more commentary on the results and about the relative ease of observing pre-seismic deformations, we added additional comments on pages 11, 12, and 13 of the revised manuscript t and a proper reference (Ref. [67]).

Regarding the specific case of the 2019 Mirpur earthquake, which occurred in Pakistan, it occurred in a region where the tectonic regime is predominantly compressional due to the collision between the Indian Plate and the Eurasian Plate. Detecting pre-seismic deformations in such settings can be challenging.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper uses Sentinel-1 SAR data to study earthquake-induced surface movements. Through interferogram analysis and time series inversion, the authors obtain the surface deformation variables caused by earthquakes along active faults in the Mirpur area before, during and after the earthquake and determined that there is a previously undiscovered blind fault in the area, which is of great significance for revealing potential geological activity areas and understanding earthquake risk management. However, there are still some deficiencies, and it is recommended to be accepted after modification:

1. The "ascending swath of Sentinel-1 IW SLC images" part in Figure 1-a of the article is not shown by a green rectangle. If the image is incorrectly used or the text is incorrectly expressed, please correct it. Is the “high-moderate-low” classification standard for earthquake intensity in Figure 1-b too general?

2. The epicenter position in Figure 2 of the article is represented by a green star. Is it confused with the epicenter position in Figure 1? If the image is used incorrectly or the text is incorrectly expressed, please correct it.

3. In chapter 2.1, When using the SRTM Digital Elevation Model (DEM) for co-registration and terrain stripe removal, is the 30m resolution DEM model accurate enough in partially rugged terrain areas?

4. In Chapter 3.1, some content can be added to explain the reasons for selecting the “ A-A’ ” and “ B-B’ ” dotted lines as the focus of analysis, which will make the content more complete. And standardize the coordinate axes of the two graphs a and b in Figure 6 to make them as consistent as possible.

5. Figure 7 in chapter 3.2 needs further polishing. For example, the scale is incomplete, the numbering positions of multiple pictures need to be standardized and arranged consistently, the fonts in the pictures are inconsistent, etc. Please adjust the multiple pictures in Figure 11 so that their arrangement and size are consistent.

6. Chapter 4.1 mention the impact of atmospheric or terrain artifacts on interferograms. Are there other direct or indirect influencing factors that have not been selected and considered? In addition, Section 2.1 of this article mentioned that APS can remove atmospheric artifacts. Why is there still the influence of atmospheric artifacts? Is it due to incomplete correction?

7. Chapter 4.2 "Ground Faulting and Deformation" lacks explanation and analysis and it's not appropriate to put it in the discussion.

8. The following literature maybe useful for your improvement:

① Experimental study on instability mechanism and critical intensity of rainfall of high-steep rock slopes under unsaturated conditions. International Journal of Mining Science and Technology, 2023, 33(10): 1243-1260.

② Investigating toppling failure mechanism of anti-dip layered slope due to excavation by physical modelling. Rock Mechanics and Rock Engineering, 2020, 53(11): 5029-5050.

This paper uses Sentinel-1 SAR data to study earthquake-induced surface movements. Through interferogram analysis and time series inversion, the authors obtain the surface deformation variables caused by earthquakes along active faults in the Mirpur area before, during and after the earthquake and determined that there is a previously undiscovered blind fault in the area, which is of great significance for revealing potential geological activity areas and understanding earthquake risk management. However, there are still some deficiencies, and it is recommended to be accepted after modification:

1. The "ascending swath of Sentinel-1 IW SLC images" part in Figure 1-a of the article is not shown by a green rectangle. If the image is incorrectly used or the text is incorrectly expressed, please correct it. Is the “high-moderate-low” classification standard for earthquake intensity in Figure 1-b too general?

2. The epicenter position in Figure 2 of the article is represented by a green star. Is it confused with the epicenter position in Figure 1? If the image is used incorrectly or the text is incorrectly expressed, please correct it.

3. In chapter 2.1, When using the SRTM Digital Elevation Model (DEM) for co-registration and terrain stripe removal, is the 30m resolution DEM model accurate enough in partially rugged terrain areas?

4. In Chapter 3.1, some content can be added to explain the reasons for selecting the “ A-A’ ” and “ B-B’ ” dotted lines as the focus of analysis, which will make the content more complete. And standardize the coordinate axes of the two graphs a and b in Figure 6 to make them as consistent as possible.

5. Figure 7 in chapter 3.2 needs further polishing. For example, the scale is incomplete, the numbering positions of multiple pictures need to be standardized and arranged consistently, the fonts in the pictures are inconsistent, etc. Please adjust the multiple pictures in Figure 11 so that their arrangement and size are consistent.

6. Chapter 4.1 mention the impact of atmospheric or terrain artifacts on interferograms. Are there other direct or indirect influencing factors that have not been selected and considered? In addition, Section 2.1 of this article mentioned that APS can remove atmospheric artifacts. Why is there still the influence of atmospheric artifacts? Is it due to incomplete correction?

7. Chapter 4.2 "Ground Faulting and Deformation" lacks explanation and analysis and it's not appropriate to put it in the discussion.

8. The following literature maybe useful for your improvement:

① Experimental study on instability mechanism and critical intensity of rainfall of high-steep rock slopes under unsaturated conditions. International Journal of Mining Science and Technology, 2023, 33(10): 1243-1260.

② Investigating toppling failure mechanism of anti-dip layered slope due to excavation by physical modelling. Rock Mechanics and Rock Engineering, 2020, 53(11): 5029-5050.

Author Response

We thank the Reviewer for his punctual and valuable comments which contributed to improving the paper.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

This manuscript can be accepted after the improvement of language.

This manuscript can be accepted after the improvement of language.