Inversion of seismic intensity data for the determination of three-dimensional attenuation structures in the central gap region of Himalayas

Abstract

The central gap region of Himalaya, which lies in the northern part of the Indian subcontinent, is exposed to great seismic hazard. A three-dimensional attenuation structure (Q) of this region is obtained using the intensity data of four earthquakes (M 4.3-7.0) in the central Himalayan gap region and the damped least square inversion scheme. The technique is based on that given by Hashida and Shimazaki (J Phys Earth 32:299-316, 1984). The obtained Q structure explains the spatial distribution of isoseismals of the stronger earthquakes, which occurred in the recent past. The study area covers the Tehri town, which is the locale of one of the biggest earth fill dams of height 260 m. The spatial distribution of Q suggests that the Tehri town area is surrounded by lower Q medium, and hence any large earthquake in Tehri will pose great seismic hazard.

Three-dimensional shear-wave quality factor, Qs(f), model for south-central Gulf of California, Mexico obtained from inversion of broadband data

“…The results of the inversion depend on the quality of input data (e.g. Joshi 2007). In the present work, the input data consists of the initial velocity model, the initial shear wave attenuation model, hypocenters distances and distribution of the selected events and the S-wave window chosen to calculate the spectral acceleration values.…”

Seismicity and structure of the Indian subcontin

“…It is one of the important parameters that not only describes velocity and thermal structure, volcanism and subduction zones, but characterizes earthquake source and path effects (intrinsic attenuation) ultimately defining the level of earthquake ground motions for hazard assessment. The frequency-dependent 3-D attenuation structure of the crust is obtained from inversion of the spectral acceleration using strongmotion (Joshi et al, 2010;) and seismic intensity data (Joshi 2007) in Kumaon Himalaya and central gap region of Himalayas, which can be used for prediction of ground motion and hence for hazard assessment of the region. Seismic wave attenuation has been investigated for different parts of India on local to regional scale using the high-frequency (>1Hz) direct body and the following coda waves; these waves in this frequency band resolves features of the crust and upper mantle with a scale length of the order of few kilometers in crust to few hundred kilometers in upper mantle.…”

Seismic Attenuation From Ambient Noise Across the North Sea Ekofisk Permanent Array

“…It can also be used to locate subsurface structures such as when investigating the presence of tunnels or mine workings, as tunnels and any subsurface void cause Q anomalies (Morton et al, 2016). Q is also used in Amplitude Versus Offset analysis to compensate for seismic wave attenuation (Dasgupta & Clark, 1998;Sain et al, 2009;Zhang & Ulrych, 2002) and in seismic hazard analysis and earthquake engineering to estimate ground acceleration due to earthquakes, as attenuation must be taken into account when predicting wave amplitudes (Allen et al, 2007;Joshi, 2007;McNamara et al, 2014;Parolai, 2014;Raghu Kanth & Iyengar, 2007). It can be used as an indicator of the presence of hydrocarbons (Carcione, 2000;Dasgupta & Clark, 1998;Dvorkin & Mavko, 2006) or for correcting seismic data to improve resolution when using standard imaging techniques (Zhang & Ulrych, 2002).…”