IGPP is pleased to invite you to join its Winter 2021 Virtual Seminar Series presentation featuring IGPP's Haoran Meng. Dr. Meng's talk, "Resolving finite-source attributes of the 2019 Ridgecrest earthquake sequence using second-moment method" will be available via Zoom on Tuesday, March 16, 2021, starting at 12:00pm. The seminar will be hosted on Zoom link here (password = ridgecrest).
Date: Tuesday, March 16, 2021
Time: 12:00 pm, Pacific Time
Note: This meeting will be recorded. Please make sure that you are comfortable with this before registering.
Abstract: Resolving earthquake rupture process is essential to understand earthquake physics and mitigate seismic hazards. Such processes of moderate and small seismic events are usually resolved using spectral fitting methods with pre-assumed physical rupture models. In this study, we apply a model-free method to estimate the second-degree seismic moments of 39 M 3.8 to 5.5 earthquakes in the 2019 Ridgecrest sequence using local broadband seismic networks. The second moments of an earthquake describe the finite source attributes including rupture length, width, duration, and directivity. Our observations show weak and moderate rupture directivities with propagation directions both parallel and perpendicular to the rupture strike of the Mw 7.1 mainshock. Interestingly, there is a lack of spatial clustering of rupture directivities in this previously unmapped fault system. With the resolved rupture lengths and widths, we also estimate the stress drops ranging from 2 to 200 MPa with a median of 47 MPa. This probably indicates these resolved earthquakes released a large portion of the shear stress on the faults considering the estimate on the order of 25-40 MPa in previous studies.