Systematic Search for Repeating Earthquakes Along Haiyuan Fault in Northeast Tibet

Date: 4/26/2019

Time: 06:00 PM

Room: Grand Ballroom

The Haiyuan fault is a major left-lateral fault along the northeastern boundary of Tibet Plateau. Since the 20th century, two great earthquakes (1920, Ms8.5; 1927, Ms8.0) have occurred on this fault. The Tianzhu seismic gap was sandwiched between these two earthquake rupture zones. Shallow creep has been observed from geodetic data along some portion of the Haiyuan fault (Jolivet et al., 2013). However, it is still not clear the depth extent of shallow creep, and whether it is capable of driving repeating microearthquakes that occur virtually at the same location at different times. Here we conduct a systematic search for repeating earthquakes along the Haiyuan fault based on the 10 years seismic data. Specifically, first, we compute cross-correlations (CCs) among all events listed in the regional earthquake catalogue, and identify all repeating event pairs with median (or mean) CC value above 0.90. We then group repeating pairs into clusters using an Equivalency Class (EC) algorithm. Finally we extract differential times for P and S waves and use hypoDD program to relocate them in each cluster. Our next step is to recompute their stress drops and average slips, and use them to estimate the aseismic creep at depth. We also plan to use them to measure temporal changes of seismic velocity at depth. Updated results will be presented at the meeting.

Presenting Author: Zhigang Peng

Authors