Structure of the crust and uppermost mantle of the Yanshan Belt and adjacent regions at the northeastern boundary of the North China Craton from Rayleigh Wave Dispersion Analysis

<p>The territory of Myanmar, situated at the eastern flank of the India-Asia collision zone, is characterized by complex tectonic structure and high seismicity. From west to east, this region consists of three nearly NS-trending tectonic units: the Indo-Burma Ranges, the Central Basin and the Shan Plateau. Detailed structure of the crust and uppermost mantle beneath Myanmar can provide crucial constraints on regional tectonics, subduction dynamics as well as seismic hazard assessment. Yet seismic velocity structure beneath this region is poorly determined due to sparse regional seismic networks.</p><p>In this study, we utilize seismic data recorded at 80 broadband stations in Myanmar, among which 70 stations were deployed in 2016 under the project of China-Myanmar Geophysical Survey in the Myanmar Orogen (CMGSMO), 9 stations are operated by IRIS and the remaining one is from GEOFON. We measured the Rayleigh-wave phase velocity dispersion from the ambient noise cross-correlations at periods between 5 s and 40 s by using the automatic frequency-time analysis (AFTAN). A fast marching surface wave tomography (FMST) approach was then adopted to invert the 2-D phase velocity maps in the study region. Our preliminary results show variable crustal structure across central Myanmar, with a strong low-velocity zone north of 22&#176;N in the Indo-Burma Ranges. Since Rayleigh-wave dispersion is more sensitive to absolute velocity speed than to velocity contrasts, the ongoing study jointly inverts the dispersion data with P-wave receiver functions to better determine the velocity discontinuities and thus provides tighter constraints on the shear-velocity structure beneath central Myanmar.</p>

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1-D velocity model for the North Korean Peninsula from Rayleigh wave dispersion of ambient noise cross-correlations

Journal of Seismology ◽

10.1007/s10950-019-09891-6 ◽

2019 ◽

Vol 24 (1) ◽

pp. 121-131 ◽

Cited By ~ 2

Author(s):

Sang-Jun Lee ◽

Junkee Rhie ◽

Seongryong Kim ◽

Tae-Seob Kang ◽

Chang Soo Cho

Keyword(s):

Rayleigh Wave ◽

Korean Peninsula ◽

Ambient Noise ◽

Goodness Of Fit ◽

Seismic Velocity ◽

Wave Dispersion ◽

Velocity Models ◽

The North ◽

Cross Correlations ◽

Rayleigh Wave Dispersion

AbstractMonitoring seismic activity in the north Korean Peninsula (NKP) is important not only for understanding the characteristics of tectonic earthquakes but also for monitoring anthropogenic seismic events. To more effectively investigate seismic properties, reliable seismic velocity models are essential. However, the seismic velocity structures of the region have not been well constrained due to a lack of available seismic data. This study presents 1-D velocity models for both the inland and offshore (western East Sea) of the NKP. We constrained the models based on the results of a Bayesian inversion process using Rayleigh wave dispersion data, which were measured from ambient noise cross-correlations between stations in the southern Korean Peninsula and northeast China. The proposed models were evaluated by performing full moment tensor inversion for the 2013 Democratic People’s Republic of Korea (DPRK) nuclear test. Using the composite model consisting of both inland and offshore models resulted in consistently higher goodness of fit to observed waveforms than previous models. This indicates that seismic monitoring can be improved by using the proposed models, which resolve propagation effects along different paths in the NKP region.

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