Using 3D Crustal Velocity Models and Multiazimuth Back Projection to Image Rupture Processes of Intermediate-sized Earthqukes
Description:
We have developed a multiazimuth backprojection method, which allows us to image intermediate-sized earthquake rupture processes by using regional networks, 3D crustal velocity models, and may achieve depth resolution. We applied this approach to two earthquakes occurred in 2019 and 2020. The time-integrated images for the Mw6.4 foreshock and Mw7.1 mainshock agree with the fault geometry delineated by the aftershock distributions. Backprojection images at different times illustrate the detailed rupture processes for these two events. For instance, the Mw6.4 foreshock initialized close to the hypocenter, then the rupture propagated along a northwest trending fault with an average velocity of 1.0 km/s, and finally jumped to a southwest trending fault and propagated about 20 km with a velocity about 1.5 km/s. In contrast, the Mw7.1 mainshock initialized near the hypocenter, then propagated to the northwest upon reaching the Coso volcanic field with an average velocity of 1.4 km/s, and later turned to the southeast and propagated along the main fault zone with a complex bilateral process and a velocity about 0.6 km/s.
For the 2020 Mw 6.5 Stanley earthquake, more than 35% nondouble-couple component in long-period point-source solutions indicate a more complex source than slip on a planar fault. Combining backprojection, finite fault inversion and InSAR analysis, we find that the Stanley earthquake ruptured a pair of opposing-dip faults offset by a 10-km-wide step, including an unmapped northern subfault with predominantly strike-slip faulting and a southern subfault subparallel to the Sawtooth fault with predominantly normal faulting. This study reveals that a composite rupture process with strike-slip and normal faulting is typical for earthquakes located near the northern boundary of the Centennial Tectonic Belt (CTB), which is distinct from the predominantly normal faulting in the central CTB.
Session: Advances in Reliable Earthquake Source Parameter Estimation - III
Type: Oral
Date: 4/16/2025
Presentation Time: 02:30 PM (local time)
Presenting Author: Hejun
Student Presenter: No
Invited Presentation:
Poster Number:
Authors
Hejun Zhu Presenting Author Corresponding Author zhuhj@sustech.edu.cn Southern University of Science and Technology |
Jidong Yang jidong.yang@upc.edu.cn China University of Petroleum (East China) |
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Using 3D Crustal Velocity Models and Multiazimuth Back Projection to Image Rupture Processes of Intermediate-sized Earthqukes
Category
Advances in Reliable Earthquake Source Parameter Estimation