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Source Stress Drop for Continental Collision Zones: Deviation From “Textbook” Earthquake Models

Continetal faults are known for more irregular distribution of slip compared to their subduction counterparts, as often exhibited in differenct source kinematics and the corresponding stress drop of earthquakes. Immature faulting, believed to be one of the main causes for this behavior, is a property of continental collision zones. In this context, we present the results of our study of earthquake slowness parameter, THETA, for the M_w>5.0 CMT events in Iran between 1990-2022 as a measure of stress drop. As the energy-to-moment ratio of ruptures, this quantity is obtained using only teleseismic body waves and is largely invariant of source mechanism. Statistical analysis of our dataset reveals an ~0.6 units increase in slowness values for the Iranian earthquakes, corresponding to four times higher stress drops in an active collision zone. We attribute the variations of SIGMA=0.3 logarithmic units in the calculated slowness to the seismotectonic zoning of Iran, revealing different slowness trends in various faulting regimes of the region. This conclusion is in agreement with the different rates of convergence along the deformation bands in the Iranian Plateau.

Session: Earthquake Source Parameters: Theory, Observations and Interpretations [Poster]

Type: Poster

Room: Ballroom

Date: 4/18/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Amir Salaree

Student Presenter: No

Additional Authors