Triggered Tectonic Tremors in the Western Makran Subduction Zone Following Large Teleseismic Earthquakes

Abstract Large, distant earthquakes can trigger deep tectonic tremors in subduction zones and other seismically active regions. Although most documented cases occur along the Pacific Rim, only a few have been identified in the Alpine-Himalayan orogenic belt and the Sumatra-Java subduction zones. The Makran subduction zone (MSZ), off the coast of Iran and Pakistan, is an active subduction zone expected to generate similar tremors. However, no deep tectonic tremors have been reported in the MSZ to date. Using seismic data collected from a newly deployed seismic array from March 2017 to September 2018 in the western MSZ (WMSZ), we identified long-duration triggered tectonic tremor signals following the 2017 Mw 8.2 Chiapas, Mexico, earthquake and likely the 2017 Mw 7.3 Sarpol Zahāb earthquake near the Iran–Iraq border. Tremor sources triggered by the 2017 Mw 8.2 Chiapas mainshock were located near the border between the accretionary wedge and the Jaz Murian depression—an extensional forearc basin. Although it is not clear whether these tremors occurred on the WMSZ plate interface or the deep roots of other crustal faults such as the north-dipping Bashagard thrust fault, we confirmed that tectonic tremors exist in the WMSZ and can be triggered or modulated by transient dynamic stresses on the order of a few kilopascals. This study contributes to further understanding of the subduction process and slip behaviors of aseismic slip transients in the WMSZ.