Structure and Stress Field of the Lithosphere Between Pamir and Tarim

Abstract

The salient Pamir plateau is part of the India-Asia collision system. It is offset by ∼300 km to the north in relation to the adjacent Tibet plateau and protrudes between the Tajik basin in the west and the cratonic block of the Tarim basin in the east (e.g., Lu et al., 2008). The northern Pamir and the Kunlun of northwestern Tibet comprise subduction-accretion-arc complexes accreted to and built on Asian continental basement. The central and southern Pamir and the Karakorum and Hindu-Kush represent Gondwana-derived microcontinents and subduction-accretion-arc complexes (Figure 1; Burtman & Molnar, 1993;Schwab et al., 2004).Beneath the Pamir, a band of intermediate-depth (50-250 km) earthquakes, extending from the southwestern Pamir northeastward into the central Pamir, bends eastward, and shows diminished earthquake activity beneath the eastern Pamir (Figure 2; Pegler & Das, 1998; Sipp, Schurr, Yuan, et al., 2013). Receiver function images (Schneider et al., 2013) and the analysis of guided waves (Mechie et al., 2019) show that the earthquakes in the western and central Pamir reside in a 10-15 km thick, E-to S-dipping low velocity zone (LVZ) connected to the Asian lithosphere; seismic velocities indicate that the LVZ represents continental crust, which has-together with the underlying mantle lithosphere-been interpreted as the Asian slab (Mechie

Intracontinental deformation of the Tianshan Orogen in response to India-Asia collision

“…Squares denote seismic stations used in this study from the Middle AsiaN Active Source project (MANAS) and other networks (KR and XW). Green and blue circles show earthquakes at shallow 65 (≤70 km) and intermediate 66 , 67 (70–300 km) depths. The purple points with numbers denote the onset of rapid cooling derived from thermochronological studies 13 , 14 .…”

Two kinematic transformations of the Pamir salient since the Mid-Cenozoic: Constraints from multi-timescale deformation analysis

“…To the east of a seismicity gap between 74.4 °E and 74.9 °E, the southdipping slab abruptly overturns to the north. A slab tear may have occurred at the boundary, showing flipping of the slab dips (Bloch et al, 2021). Below the southern portion of the eastern Pamir, the observed double Moho structure, P-wave velocity structure, and seismicity distribution indicate that the Pamir slab has underthrusted eastward beneath the Tarim lithospheric mantle (Bloch et al, 2021;Xu Q. et al, 2021).…”

“…A slab tear may have occurred at the boundary, showing flipping of the slab dips (Bloch et al, 2021). Below the southern portion of the eastern Pamir, the observed double Moho structure, P-wave velocity structure, and seismicity distribution indicate that the Pamir slab has underthrusted eastward beneath the Tarim lithospheric mantle (Bloch et al, 2021;Xu Q. et al, 2021). South of the arcuate Pamir slab, the presence of a high-velocity anomaly was interpreted as the underthrusting cratonic Indian lithosphere (Sippl et al, 2013a;Li et al, 2018;Liang et al, 2020;Bloch et al, 2021).…”

“…Beneath the Pamir-Hindu Kush region, a ~500-km-long belt of intermediate-depth earthquakes extends from the Hindu Kush northeastward into the Central Pamir and then bends eastward into the eastern Pamir (Kufner et al, 2018;Bloch et al, 2021). Recent studies on the intermediate-depth earthquakes and teleseismic tomography have distinctly depicted the lithospheric configuration of the Pamir (e.g., Sippl et al, 2013b;Kufner et al, 2016;Schneider et al, 2019;Liang et al, 2020;Xu Q. et al, 2021).…”

“…Beneath the Pamir, receiver function images, local earthquake tomography, and observation of guided waves have revealed an arcuate Pamir slab (lower crust and upper mantle) with various dips (Sippl et al, 2013a;Sippl et al, 2013b;Schneider et al, 2013;Li et al, 2018;Mechie et al, 2019;Bloch et al, 2021;Xu Q. et al, 2021). The Pamir slab dips to the east under the western South Pamir and then bends south-dipping under the Central Pamir.…”