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Revisiting Seismic Hazard in Iran: Role of Stress Drop in Peak Ground Acceleration in a Zone of Immature Faulting

The continental collision between the Arabian shield and Eurasia has resulted in an average of ~15,000 earthquakes in Iran every year, having led to more than $3 billion of economic loss over the past decade. The existing seismic hazard models for the country do not consider rupture kinematics on the complex, immature fault zones in the region. Here, we use the source slowness parameter, Θ, obtained from teleseismic data, to evaluate the frequency content of dip-slip CMT events during 1999-2022 in Iran for which strong motion data is available from the Iranian network. The advantage of Θ algorithm is its robustness with sparse network coverage and the use of only the first several seconds of body waves train. We then compare the anomalies in rupture velocity and consequently the stress drop to the locally recorded PGA values by the Iranian strong motion network, as well as to spectral variations predicted by attenuation equations between 2–5 Hz, considering various site properties. Our results reveal a strong correlation between earthquake source slowness parameter (with ∼0.2 logarithmic unit standard deviation) and the anomalies in the observed PGA. This result reaffirms the notion that slowness parameter is a good measure of observed ground shaking and as such can be used as an identifier for the seismic hazard in the near-field. We also find that our spectral dataset deviates from existing seismotectonic zonings of Iran and thus we propose modifications to the current hazard models for the country.

Session: Opportunities and Challenges in Source Modeling for Seismic Hazard Analysis

Type: Oral

Room: 208A

Date: 4/20/2023

Presentation Time: 11:00 AM (local time)

Presenting Author: Amir Salaree

Student Presenter: No

Additional Authors