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The October 2023 Herat, Afghanistan Earthquake Quadruplet - Aftershock Locations and Moment Tensors

Description: 

A series of four magnitude M_w=6.3 earthquakes struck the Herat province in northwestern Afghanistan in October 2023 causing widespread destruction and killing almost 1,500 people (information from the World Health Organization). All four main events have thrust mechanisms. Rupture likely occurred on blind thrust faults as no surface ruptures have been reported precluding a clear interpretation of fault dip direction(s). Fault segmentation, which could cause delayed rupture on adjacent segments, cannot be addressed due to the low resolution of existing earthquake locations as the events occurred far from seismic networks. The distance from the epicentral area to the closest permanent seismic stations in northeastern Iran is about 150 km and to the closest station in the east, the IRIS station in Kabul, about 650 km. To improve understanding of spatial relations and faulting styles, we use data from the Iranian seismic networks and from other stations at regional distances to locate the sequence and to obtain moment tensor solutions. Our preliminary results from locating over 100 earthquakes from 7 October to 20 November 2023 reveals a roughly 50x20 km distribution elongated in the west-northwest direction that coincides well with the uplift region from InSAR data (from LiCSAR). Moment tensors of the main events and 10 aftershocks (M_w 4.1-5.8) indicate predominantly thrust faulting on roughly east-west oriented faults. The shallow centroids of ~3-5 km for the main events suggest ruptures may have reached close to the surface perhaps explaining the localized strong destruction. Our results are consistent with rupture on a blind fault structure north of the right-lateral Herat (or Hari Rud) fault and south of the Siakhubulak fault. The Herat fault system is the dominant physiographic feature that connects the Arabia-Eurasia and India-Eurasia collision zones and, combined with sub-parallel thrust faults such as the one(s) active in 2023, accommodates any remaining relative plate motions.

Session: Illuminating Complex, Multiplet Earthquake Sequences at Kahramanmaras (Turkiye), Herat (Afghanistan), and Beyond - I

Type: Oral

Date: 5/2/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Jochen

Student Presenter: No

Invited Presentation: 

Authors