A 3‐D Shear Wave Velocity Model for Myanmar Region

Abstract

Myanmar is located at the eastern margin of the ongoing Indo-Eurasian collision system, has experienced a complex tectonic history and is threatened by a high level of seismic hazard. Here we develop a crustal scale 3-D seismic velocity model of Myanmar, which is not only critical for understanding the regional tectonic setting and its evolution but can also provide the foundation for a variety of seismological studies, including earthquake location determinations, earthquake focal mechanism inversions, and ground motion simulations. We use the newly deployed Earth Observatory of Singapore-Myanmar broadband seismic network and other seismic stations in and around Myanmar to study the station-based 1-D velocity structure through a joint inversion of receiver functions, H/V amplitude ratio of Rayleigh waves, and surface wave dispersion measurements. Our results reveal a highly variable crustal structure across Myanmar region, characterized by a series of N-S trending sedimentary basins, with thicknesses up to~15 km in central Myanmar and an~5-km step in the depth of the Moho across the Sagaing-Shan Scarp fault system. We interpolate our station-based 1-D velocity profiles to obtain an integrated 3-D velocity model from southern Bangladesh to Myanmar. Using three regional earthquakes located to the south, within, and north of the seismic network, we show that our proposed model performs systematically better than the CRUST 1.0 model for both Pnl waves and surface waves. Our study provides a preliminary community velocity model for the region, with further refinements and interpretations anticipated in the near future.

Mantle Transition Zone Structure Beneath Myanmar and Its Geodynamic Implications

“…The second model adopts the global P‐wave velocity model (UU‐P07, van der Meer et al., 2018) and a constant perturbation ratio of 1.73 for calculating S‐wave velocity. The shallow structure in these two models was replaced by Myanmar Hybrid version 1 (Wang et al., 2019), as applied to the preferred model. The results constructed with both P‐ and S‐velocity models are similar to those obtained with the 1‐D velocity model (Figure 6), but the D660 at the longitude range of 93°E‐96°E is deepening (Figure ).…”

“…Each station was equipped with a Güralp CMG‐3ESP or a Nanometrics Trillium 120PA seismometer and a Trimble Ref Tek 130 digitizer with sampling rate of 40 Hz. In addition to the CMGSMO seismic network, we included 34 stations operated by the Earth Observatory of Singapore since October 2016, with an average spacing of ∼150 km (Wang et al., 2019). The remaining nine stations belong to the Myanmar National Seismic Network and were requested from the Incorporated Research Institutions for Seismology Data Management Center.…”

“…A portable array of 71 stations with a spacing of 15-40 km were deployed in June 2016 under the China-Myanmar Geophysical Survey in the Myanmar Orogen (CMGSMO) project and acquired over 1 year of continuous seismic data (Mon et al, 2020 In addition to the CMGSMO seismic network, we included 34 stations operated by the Earth Observatory of Singapore since October 2016, with an average spacing of ∼150 km (Wang et al, 2019). The remaining nine stations belong to the Myanmar National Seismic Network and were requested from the Incorporated Research Institutions for Seismology Data Management Center.…”

Insight Into Major Active Faults in Central Myanmar and the Related Geodynamic Sources

“…Furthermore, the investigations were hampered by no obvious tectonic landform due to sedimentation and/or rapid erosion. Steckler et al, 2016;Searle et al, 2017;Mallick et al, 2019;Wang et al, 2019). The tectonic units are delimited by different colors.…”

Slab Models Beneath Central Myanmar Revealed by a Joint Inversion of Regional and Teleseismic Traveltime Data

“…We utilize P‐wave traveltime observations recorded by seismic stations in Myanmar, Bangladesh, and Thailand (Figures 1b and Figures S3 and S4). The Earth Observatory of Singapore (EOS) has been maintaining a seismic monitoring network comprising 30 broadband seismic stations throughout Myanmar, most of which have been in operation since July 2017 (X. Wang et al., 2019). In addition, EOS has deployed six broadband and 22 short‐period seismic stations in eastern Bangladesh since June–September 2016.…”