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

Abstract

Myanmar, one of the most active tectonic regions in the world, endures the risk of destructive earthquakes. Based on seismic data recorded at the recently deployed dense array of the China-Myanmar Geophysical Survey in the Myanmar Orogen (CMGSMO), we detect 854 and locate 599 shallow earthquakes with high precision and determine the focal mechanisms of 40 earthquakes. We identify two NW-SE trending fault zones accommodating dextral strike-slip earthquakes beneath the Central Basin, indicating potential seismic risk in the region. We also recognize a nearly N-S trending seismic zone in the overlying Indo-Burma Ranges (IBR) crust near the Kabaw Fault (KBF). The earthquakes within this seismic zone mostly show thrusting focal mechanisms. Our results suggest that strike-slip deformation dominates to the east of the KBF, while shortening is mainly confined to the west of the KBF in Central Myanmar.Plain Language Summary Myanmar in Southeast Asia suffers from disasters resulting from destructive earthquakes. However, the present knowledge on their causative faults is limited due to the deployment of few seismic observation stations in Myanmar. We deployed a seismic observation network containing 71 stations for 1.5 years and tried to identify unknown causative faults and their characteristics by studying the small earthquakes there. Our results suggest that larger areas than previously expected in Myanmar may encounter significant seismic hazards. More attention to mitigating hazards should be paid to the Central Basin and western mountain areas, where densely populated cities are located.

Mantle Transition Zone Structure Beneath Myanmar and Its Geodynamic Implications

“…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). 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.…”

“…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.…”

Sinking Slab Stress and Seismo‐Tectonics of the Indo‐Burmese Arc: A Reappraisal

“…Data used in this study are obtained from the ISC (Engdahl et al., 2020) (http://www.isc.ac.uk/isc%2Dehb/search/catalogue/), NEIC (Masse & Needham, 1989) (https://earthquake.usgs.gov/earthquakes/search/), GCMT (Ekström et al., 2012) (https://www.globalcmt.org/CMTsearch.html), and Mon et al. (2020). All the stress inversion model input data used in this study are presented as a supplementary text as well as available at the website (https://doi.org/10.5061/dryad.k3j9kd57q).…”

“…Depth-wise color-filled and magnitude-wise size-scaled circles are earthquake epicentral locations. Data span and sources are: 1900-1963 (NEIC) (Masse & Needham, 1989), 1964-2017Engdahl et al, 2020), 2017Masse & Needham, 1989(Mon et al, 2020. observations, it is counterargued that the Indian slab is a relict remnant of the previous subduction history and presently acts as a slip surface for the northward motion of the MP (Rangin, 2017).…”

The January 11, 2018, Mw 6.0 Bago‐Yoma, Myanmar Earthquake: A Shallow Thrust Event Within the Deforming Bago‐Yoma Range

“…The relative P-wave arrival times at station M011 and M012 between all five events in this cluster directly shows the sensitivity to the event location (Figures 7a-7c), where the event nearest to station M011 (20180207_1638) has the earliest P-arrival while the event furthest from M011 (20180205_1655) has the latest P-arrival and vice versa at station M012. These three events align nicely along the strike (98°) of one of the fault plane solutions (Figure 4d; Table 1), indicating it is more likely that the near E-W oriented strike-slip fault had ruptured during the sequence, which is almost perpendicular to the active faults that were recently found in northern Myanmar (Mon et al, 2020). The northernmost strikeslip event (Figure 5) suggests that the rupture occurred on another strike-slip fault that is probably parallel to the fault defined by the other three strike-slip events.…”