@hriston_bg You can find the unwrapped results as follows:
Actually, it is one of the case studies in my Ph.D. thesis that I am busy in processing and modeling. Now, I don’t have any external sources to use.
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The first step before doing earthquake modeling is to convert the unwrapped phase to range-change in meters with the standard formula.
Remember that unwrapping returns still phase in radians, and you should do phase to height conversion to get values in meters
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Yes I know. I mean that the displacement of this study area, caused by the earthquake, is not in the range of the meter.
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Dear all,
Did anybody use “GBIS” software and “PYROCKO” python package to model the earthquake and get the source parameters using the InSAR results?
Best regards,
Sayyed
Dear all,
I would like to find the fault related to my considered earthquake for modeling using the InSAR results but I am worried about which one can be effective on this earthquake.
According to the above figure, could you please guide me to find suitable and correct faults?! In this figure, you can see the location of epicenter reported by CMT and USGS websites.
Best regards,
Sayyed
The best option in this case is,
1- Create different buffers around the epicenter each one should cover some of these faults.
2- According to the history of the faults the most and recent active faults should be remain within the buffer and exclude the other passive, or not active for recently,
3- Search the remaining active faults the history of earthquake, epicenter the depth and the magnitude, make a simple statistics, take in account the most redundant of high magnitude, compare the result with the epicenter depth and magnitude of above mentioned.
4- Check out also which part of the fault is most active, related to these close to the epicenter.
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Thank you so much for your nice comments. Did you see the difference between the coordinates of epicenters reported by CMT and USGS as much as this study area?
In fact according to the,
" Every time an earthquake occurs in the world, thousands of seismograms are recorded at hundreds of seismographic stations. From these seismograms, information about the earthquake can be quickly inferred, including its epicenter, depth, as well as its intensity. These so-called Central Moment-Tensor (CMT) solutions are routinely determined by Lamont-Dohertywww.globalcmt.org."
Source: http://global.shakemovie.princeton.edu/science.jsp
It shouldn’t be a difference,
But please check up more, or somebody else could give an opinion,
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@EJFielding Sorry for disturbing you but do you know why there is the difference between the locations of epicenter reported by GCMT and USGS?
Hello @SMJMirzadeh, the USGS epicenter is estimated from high-frequency body waves (P and S, primarily) and represents an estimate of the location where the earthquake started. They usually update their epicenter location about a month after the earthquake when they get additional data from stations closer to the earthquake. The Global Centroid Moment Tensor (GCMT) is calculated from very low-frequency surface waves and the location is the centroid of the entire earthquake slip. The real difference between the epicenter and the centroid should be small for a magnitude 6 earthquake because the rupture area is not large. The difference between the USGS epicenter and GCMT centroid here is more likely due to differences in the input data and the accuracy of the Earth seismic velocity models that they use. The GCMT centroids are often biased substantially by regional Earth structure as they use a general seismic velocity model, so I would expect the USGS epicenter to be more accurate.
Have you checked the epicenter location for the mainshock and aftershocks from the regional Iranian networks? Since they have stations much closer than the global networks, they should be more accurate and they should have locations for smaller aftershocks that could help see the likely location of the fault that ruptured.
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It looks like none of those previously mapped faults can explain the coseismic deformation of this earthquake. I would recommend using the nodal planes estimated from the USGS W-phase moment tensor or the GCMT to start for the strike and dip of the fault. Then you need to try different locations and depths. I have not used PyRocko, but I think it has a function to try different locations.
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@EJFielding Thank you so much for your great information. They are really useful and due to your high experiences.
You can find the distribution of the Iranian network in the following so that I determined my study area through a red circle.
I checked the location of mainshock reported by the regional network and also the locations of aftershocks. In the following picture, the green and pink pins determine the location of mainshock reported through GCMT and USGS respectively. The yellow pin specifies the location of mainshock reported by regional network. In addition, you can see the locations of aftershocks in red pins. The red triangles are two stations of the regional network which are the closest ones to my study area. I think you are right and the location reported by USGS is more accurate than the GCMT based on the regional report.
About your opinion for the fault which is related to my earthquake, it is great. I determined an area using a red circle. I think something happened there so that we can see a change in the shape of fringes. Do you think it is possible to have a rupture there?
I would like to use the SDM and GBIS packages to do the modeling. In these packages, I always tried to use the nodal planes in the following for the first values of strike and dip. I know that these values are related to fault and also auxiliary plates so that we need to determine the fault plate.
Best regards,
Sayyed
Sayyed,
Yes, it looks like there is a surface rupture in the area that you circled on your interferogram. There are clear discontinuities in the fringes. It is not sure, however, whether that surface rupture is on the same fault that caused most of the deformation at depth. Some of the earthquake fringes continue south of the discontinuity, which means the main fault continues to the south, so it seems likely that the surface rupture is on a secondary fault. I think it is more likely that the main fault is dipping to the northeast as that would be more consistent with those surface ruptures.
++Eric
@EJFielding Thank you so much for your great information. I’m so sorry to disturb you.
As I checked in USGS and also GCMT, this earthquake is a kind of mainly Reverse-Slip with a little bit movement in Strike-Slip direction. As you can see in the following (one ascending orbit and two descending orbits), I draw a black line in that clear discontinuities so that I think the direction of the main fault will be northeast-southwest. So, we will be moving in the northeast direction. Is it right? And I don’t know about the kind of Strike-Slip here which can be Left-Lateral or Right-Lateral. I think it is important to select the correct Strick and Dip values from one of the nodal planes (NP1 or NP2).
I read this document (https://www.ocean.washington.edu/courses/oc410/reading/Focal_mechanism_primer.pdf) and found some good information about the parameters. Based on what is expressed in page 6 and also the values of Rake parameter, reported by USGS (the following picture), the fault type is the pure Reverse-Slip without any Strike-Slip element. Do you confirm my view?!
