Long-term triggered seismicity on the Mosha fault by Damavand volcano, Iran: Implications on the seismic hazard of Tehran metropolis

The seismic history of the Mosha fault, largest and most active fault Eastern Tehran metropolis, its relation to Damavand volcano, highest mountain in Middle East, is investigated. We deduce that central Mosha, near Damavand, has a higher seismicity than either western or eastern segments. On 7 May 2020, an Mw 5.1 earthquake occurred on about 40 km east 10 southwest crest, it was felt intensely Tehran. Its rupture imaged located region presented relative quiescence compared parts, during last 14 years, suggesting partial locking heterogeneous distribution frictional strength this segment Mosha. significant directivity west confirmed by mainshock model, PGA distribution, early aftershocks. model suggests relatively small stress drop 2.6 bar, which consistent with comparatively high dimension 9 for earthquake, indicates easy expansion Volcano. experienced earthquakes 1930, 1955, 1983, as well microseismic activity 2020 sequence, all strongly point possible influence Volcano This corroborated observation hydrothermal zones extension sill-like young magma chamber until tomography studies. propose existing heat may increase pore pressure lowers effective normal stress, facilitates nucleation-expansion rupture, unclamps fault. could act fuse nucleate earthquakes, if extends toward west, have effect low-frequency waves reach without attenuation affect tall structures. In addition, site amplification frequencies up 16 Hz due deep sedimentary basin, mainly mid-city Tehran, will be remarkable short buildings.