Variations of the crustal thickness in Nepal Himalayas based on tomographic inversion of regional earthquake data

Abstract

Abstract. We estimate variations of the crustal thickness beneath the Nepal Himalayas based on tomographic inversion of regional earthquake data. We have obtained a low-velocity anomaly in the upper part of the model down to depths of 40 to 80 km and proposed that the lower limit of this anomaly represents variations of the Moho depth. This statement was supported by results of synthetic modeling. The obtained variations of crustal thickness match fairly well with the free-air gravity anomalies: thinner crust patterns correspond to lower gravity values and vice versa. There is also some correlation with magnetic field: higher magnetic values correspond to the major areas of thicker crust. We propose that elevated magnetic values can be associated with more rigid segments of the incoming Indian crust which cause more compression in the thrust zone and lead to stronger crustal thickening.

responses to reviewer 2

“…This result supports the passive nature of the extension, which is likely due to relative displacements of large lithospheric plates, namely, the African and Arabian plates. This looks consistent with the results of regional tomography work by Koulakov et al (2016) in which the Red Sea is associated with high-velocity anomalies in the upper mantle.…”

“…However, that area was on the margin of the model and thus had lower data density and poorer resolution. For the upper mantle, the P velocity model is similar to a recent tomography model of the entire Arabian region by Koulakov et al (2016), in which the southern part of the Gulf of Aqaba corresponds to the higher velocity anomaly at 100 and 200 km depths. Meanwhile, the large area corresponding to the Dead Sea and surrounding region coincides with the lower velocity anomaly.…”

Moho Beneath Tibet Based on a Joint Analysis of Gravity and Seismic Data

“…Seismic methods were extensively used to determine the Moho topography beneath the Tibetan Plateau, primarily including seismic reflection (e.g., Gao et al, 2013;Lu et al, 2009;Zhang & Klemperer, 2005; see Zhang et al (2013), for a review), deep seismic sounding profiles (e.g., Teng et al, 2013Teng et al, , 2014Wang et al, 2017), receiver function analysis (e.g., Kind et al, 2002;Lou et al, 2009;Singh et al, 2017;Tian et al, 2014; see Li et al (2014) for a review), and seismic tomography (e.g., Koulakov et al, 2015;Obrebski et al, 2012). Recently, some regional models for the China mainland (Li et al, 2014), Asia and adjacent areas (Stolk et al, 2013), and the global models (e.g., Szwillus et al, 2019) have been compiled by interpolating the ©2020.…”

Seismic structure beneath the Gulf of Aqaba and adjacent areas based on the tomographic inversion of regional earthquake data

“…In that study, they used synthetic tests to show the resolving capacity and limitations of such an approach. Here we use an approach similar to the one presented in Koulakov et al (2015) and show that recovery of the Moho depth variations is also possible in our case (Fig. 6).…”

“…At the same time, some authors claim that in cases of varied interfaces with sufficiently strong velocity contrasts, velocity heterogeneities at corresponding depths may give information about the relative depth variations of the interface. For example, Koulakov et al (2015), based on tomography work, have produced a map of the Moho depth variations beneath the central Himalayas. In that study, they used synthetic tests to show the resolving capacity and limitations of such an approach.…”