Fig. 5: Crustal event catalogue, GNSS rates and tectonic interpretation.
From: The Hindu Kush slab break-off as revealed by deep structure and crustal deformation
a Histograms of deep crustal seismicity (25–40 km depth, 2012–2019; this study), intermediate-depth seismicity related to break-off (160–300 km depth, 2012–2019; this study and ref. 20), and tomography results for P-wave velocity (vP) at 30 km and P-wave velocity anomaly (dvP) at 400 km depth along the longitudinal transect highlighted in (b). Positive dvP values east of 69.5°E indicate the presence of the stretched and tearing slab at depth. This longitudinal range is characterized by middle/lower crustal low-velocities. b Crustal event catalogue shallower than 40 km depth, scaled by event magnitude (see Supplementary Fig. 4 for details). Intermediate-depth seismicity (this study and ref. 20) is plotted for orientation. The depth from 40 to ~60 km is mostly aseismic. Compression(P)-axes and focal mechanisms of crustal earthquakes from single event solutions (small beach-balls) and strain inversion (large beach balls; see Supplementary Fig. 5 for details). GNSS rates with 95% confidence ellipses relative to Asia, re-evaluated based on refs. 23,59. GNSS1-2 highlight the locations of dense GNSS station profiles across the Hindu Kush. NE/NW/SE/SW-HK, north-east/north-west/south-east/south-west Hindu Kush. c Interpretation sketch illustrating the process of slab break-off and the crustal response. The slab experiences stretching and steepening during advancing break-off resulting in a greater penetration depth. Parts of the Indian crust are pulled to depth together with the slab and are buoyantly exhuming (white arrows) providing a heat input to the upper plate crust from below (wavy red arrows). Seismicity related to break-off is highlighted in pink; shallower intermediate-depth seismicity, possibly triggered by phase-transition reactions in the subducted crust, is in purple. The degree of crust-mantle coupling in the upper plate, the Hindu Kush orogen, decreases alongside the advance of slab break-off at depth. This is expressed in a change in crustal deformation style.
