Implementing a Regional 1-D Velocity Model for Locating Earthquakes for Southern Texas
Description:
Since 2018, the Texas Seismological Network (TexNet) has installed a densely distributed seismic network to monitor seismicity in southern Texas, covering the Eagle Shale play. Prior to the TexNet, a seismogenic zone has been identified using data from the Transportable Array (2009-2011). During that time, an Mw 4.8 event occurred on October 20th, 2011. In addition to the sufficient station coverage, an important factor to best constrain the earthquake hypocentral locations is to use a proper velocity model that can best reflect the regional tectonic setting and lithospheric structure. Currently the TexNet is using 1D global velocity model (i.e., IASP91) to locate earthquakes for southern Texas. While it can effectively constrain the epicentral locations, it however cannot well define the focal depth due to its overly simplified velocity content; which does not reflect the regional geology of the Eagle Ford Shale play.
To address this issue, the TexNet has decided to adapt a velocity profile obtained from a previous active-seismic experiment that used controlled sources. This experiment used two shot points as the seismic sources and sixty-one geophones to record the seismic signals. The recording array was in parallel with the trend of the Eagle Ford play roughly in NE-SW, and stretched nearly 260 km. The velocity profile sets the Moho discontinuity at 33 km depth, and mainly consists of 4 velocity layers within the crust. It places the depth of the basin-basement interface, a crucial depth constraint, at around 7 km depth. Because this active-seismic profile does not include S-wave velocity, we further used the Wadati diagram to determine the collective crustal Vp/Vs ratio for inferring Vs from Vp. We compiled a 1-D regional velocity model based on the obtained Vp and Vs. After revisiting the published catalogs, our preliminary test results have shown a much clustered seismicity running in an overall northeast-southwest direction; which comprises several secondary earthquake clusters. Going forward, we are going to do more tests to verify the robustness of this 1-D model.
Session: Network Seismology: Recent Developments, Challenges and Lessons Learned [Poster]
Type: Poster
Date: 4/15/2025
Presentation Time: 08:00 AM (local time)
Presenting Author: Dino
Student Presenter: No
Invited Presentation:
Poster Number: 22
Authors
Dino Huang Presenting Author Corresponding Author dino.huang@beg.utexas.edu University of Texas at Austin |
Victor Salles victor.salles@beg.utexas.edu University of Texas at Austin |
Katerine Vallejo kate.vallejo@beg.utexas.edu University of Texas at Austin |
Alexandros Savvaidis alexandros.savvaidis@beg.utexas.edu University of Texas at Austin |
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Implementing a Regional 1-D Velocity Model for Locating Earthquakes for Southern Texas
Session
Network Seismology: Recent Developments, Challenges and Lessons Learned