Abundant aftershock sequence of the 2015 Mw7.5 Hindu Kush intermediate-depth earthquake

Abstract

The 2015 M w 7.5 Hindu Kush earthquake occurred at a depth of 213 km beneath the Hindu Kush region of Afghanistan. While many early aftershocks were missing from the global earthquake catalogues, this sequence was recorded continuously by eight broad-band stations within 500 km. Here we use a waveform matching technique to systematically detect earthquakes around the main shock. More than 3000 events are detected within 35 d after the main shock, as compared with 42 listed in the Advanced National Seismic System catalogue (or 196 in the International Seismological Centre catalogue). The aftershock sequence generally follows the Omori's law with a decay constant p = 0.92. We also apply the recently developed double-pair double-difference technique to relocate all detected aftershocks. Most of them are located to the west of the hypocentre of the main shock, consistent with the westward propagation of the main-shock rupture. The aftershocks outline a nearly vertical southward dipping plane, which matches well with one of the nodal planes of the main shock. We conclude that the aftershock sequence of this intermediate-depth earthquake shares many similarities with those for shallow earthquakes and infer that there are some common mechanisms responsible for shallow and intermediate-depth earthquakes.

Evolution and Distribution of the Early Aftershocks Following the 2008 Mw 7.9 Wenchuan Earthquake in Sichuan, China

“…To further sharpen subsurface fault images as illuminated by these newly detected aftershocks require a systematic measurement of differential times and relocation (e.g., Shelly et al, ). We have tried to relocate the detected events by using the CC differential times and the hypoDD relocation method (Waldhauser & Ellsworth, ; Figures S11 and S12), as was done for several recent studies with the template matching method (e.g., C. Li et al, ; Shelly et al, ). However, because of the lack of adequate station coverage (especially in the NE direction of the mainshock ruptures) and reduced number of events after the relocation, we did not use this relocated catalog in this study.…”

Northern Chile intermediate-depth earthquakes controlled by plate hydration

“…Aftershocks activity has been related to fault properties as state of stress (Shebalien & Narteau, 2017), rupture processes (Poli et al, 2016), seismic coupling (Hainzl et al, 2019) and the thermal state of the slab, with colder slabs showing a greater number of aftershocks (Wiens & Gilbert, 1996). A main issue is to understand if this general decrease in the number of aftershocks is real, or it is due to the lack of near-field data (Li et al, 2018). It is thus fundamental to tackle this issue, to better assess the aftershock activity (Dascher-Cousineau et al, 2020) and get new insights about the mechanism(s) and physical conditions controlling the occurrence of IDEs.…”

The Indo–Eurasia convergent margin and earthquakes in and around Tibetan Plateau

“…The Sarez-Murghab Thrust System (SMTS) in Pamir dips towards Hindu-Kush and Himalayas, with increasingly deeper seismicity to southeast, interpreted as another intercontinental subduction zone (Schurr et al, 2014). The Pamir and Hindu Kush regions are unique in featuring intense Intermediate-depth earthquakes (IDEQs) to almost 300 km depth in an intracontinental setting (Zhan and Kanamori, 2016;Kufner et al, 2017;Li et al, 2018a), testifying to vigorous geodynamic processes in the mantle below.…”

“…5) and similar statistical behaviors, such as the Gutenberg-Richter b values and the Omori aftershock decay p values. These were used to argue that the common mechanisms responsible for shallow earthquakes may also apply for IDEQs (Li et al, 2018a).…”

“…Note bimodal distribution. (c) Map view of background seismicity (gray) and aftershocks of the 2015 M 7.5 mainshock(Li et al, 2018a). The color of aftershocks is their relative time to the mainshock.…”