Crustal structure of central Myanmar (Burma) By surface wave dispersion

Digital records of seismic waves observed at Seismic Research Observatory, Cheng Mai. Thailand have been analysed for two earthquakes in western Nepal. Digital data are processed by the floating filter and phase equalization methods to obtain surface waves free from noise. Group velocities of Love and Rayleigh waves are obtained by frequency time analysis of these noise free surface waves. The period of group velocities ranges from 17 to 62 sec for fundamental mode Rayleigh waves and from 17 to 66 sec for fundamental mode Love waves. The wave paths cross both central Myanmar (Burma) and the Indo-Gangetic plain. The group velocity data of surface waves across central Myanmar (Burma) have been obtained after correction of the data for the path across the Indo-Gangetic plain. Inversion of data gives the average crustal and subcrustal structure of central Myanmar (Burma). The modelled structure shows two separate sedimentary layers each of 8 km thick, The lower sedimentary layer forms the low velocity zone of the crust. The total thickness of central Myanmar (Burma) crust is found to be 55 km

Similarity of lithospheric structure of central and northwestern part of the Indian Peninsula inferred from observed surface wave forms

Observed surface wave forms across the central part of the Indian Peninsula and across northwestern part of the Peninsula have been considered. In a previous work, using group velocity of surface waves across former religion revealed model lithosphere IP 11. Observed surface wave forms across these two regions have been compared with synthetic seismograms using model IP 11. Observed wave forms are found to agree with synthetic one. This suggests that the average lithospheric structure of central and northwestern parts of the Indian Peninsula is similar and the Lithospheric model IP 11 is an approximation to it

Near-surface imaging from traffic-induced surface waves with dense linear arrays: an application in the urban area of Hangzhou, China

Accurate understanding of near-surface structures of the solid Earth is challenging, especially in urban areas where active source seismic surveys are constrained and difficult to perform. The analysis of anthropogenic seismic noise provides an alternative way to image the shallow subsurface in urban environments. We present an application of using traffic noise with seismic interferometry to investigate near-surface structures in Hangzhou City, eastern China. Noise data were recorded by dense linear arrays with approximately 5 m spacing deployed along two crossing roads. We analyze the characteristics of traffic-induced noise using 36 hr continuous recordings. Coherent Rayleigh surface waves between 2 and 20 Hz are retrieved based on crosscorrelations within 1 hr time windows. Robust phase-velocity dispersion curves are extracted from virtual shot gathers using multichannel analysis of surface waves and coincide with the results from active seismic data, noise beamforming analysis, and measurements with the spatial autocorrelation method (SPAC). Shear-wave velocity profiles are derived for the top 100 m of the subsurface at the array locations. The estimated shear-wave velocities from traffic noise correspond to the velocities estimated from logging data. The 2D shear-wave velocity maps reveal different soil deposits and bedrock structures in the estuarine sedimentary area. The results demonstrate the accuracy and efficiency of delineating near-surface structures from traffic-induced noise, which has great potential for monitoring subsurface changes in urban areas.