Moho Interface Modeling Beneath the Himalayas, Tibet and Central Siberia Using GOCO02S and DTM2006.0

Robert Tenzer,Cheinway Hwang,Mohammad Bagherbandi,Emmy Tsui-Yu Chang

doi:10.3319/tao.2012.11.01.02(tibxs)

Abstract

We apply a newly developed method to estimate the Moho depths and density contrast beneath the Himalayas, Tibet and Central Siberia. This method utilizes the combined least-squares approach based on solving the inverse problem of isostasy and using the constraining information from the seismic global crustal model (CRUST2.0). The gravimetric forward modeling is applied to compute the isostatic gravity anomalies using the global geopotential model (GOCO02S) and the global topographic/ bathymetric model (DTM2006.0). The estimated Moho depths vary between 60 - 70 km beneath most of the Himalayas and Tibet and reach the maxima of ~79 km. The Moho depth under Central Siberia is typically 50 - 60 km. The Moho density contrast computed relative to the CRUST2.0 lower crustal densities has the maxima of ~300 kg m-3 under Central Tibet. It substantially decreases to 150 - 250 kg m-3 under Himalayas and north Tibet. The estimated Moho density contrast under central Siberia is within 100 - 200 kg m-3.

Highlights

Starting from the 1980s systematic studies of the lithospheric structure in the Himalayas and Tibet were carried out in the frame of the GGT, IRIS/1991-92PASSCAL and INDEPTH/GEDEPTH geophysical projects. Zhao et al (1993) analyzed the seismic reflection data collected at the profile INDEPTH-I across the Himalayas
The locations of large crustal thickness further extend under the Tibetan plateau with typical Moho depths of 70 - 75 km and the maxima found in northern Tibet
The convergent tectonic plate boundaries marked distinctively by the positive gravity anomalies along the orogens are coupled with the negative gravity anomalies along the sides of subducted crust

Summary

Introduction

Starting from the 1980s systematic studies of the lithospheric structure in the Himalayas and Tibet were carried out in the frame of the GGT, IRIS/1991-92PASSCAL and INDEPTH/GEDEPTH geophysical projects. Zhao et al (1993) analyzed the seismic reflection data collected at the profile INDEPTH-I across the Himalayas. Zhao et al (1993) analyzed the seismic reflection data collected at the profile INDEPTH-I across the Himalayas. He estimated that the largest Moho depths reach ~75 km. Bagherbandi (2012) applied and compared three different isostatic methods (based on solving the VeningMeinesz Moritz models and using Parker-Oldenburg’s algorithm) to estimate the Moho depths beneath Tibet and Himalayas. According to his results the maximum Moho depths reach 67 - 72 km depending on the method applied. The gravimetric results are compared with the seismic model from the global crustal model CRUST2.0 as well as more detailed regional studies

Methodology

Isostatic gravity anomalies

Moho parameters

Findings

Discussion

Conclusions