Abstract
AbstractOn January 11, 2018 (18:26 UTC), a Mw 6.0 earthquake occurred approximately 30 km west of the Sagaing Fault in the Bago‐Yoma Range (BYR). Using a local broadband seismic network and regional seismic stations, we refine the locations and moment tensors of the earthquake sequence. We relocate 98 earthquake epicenters and determine the focal mechanism and centroid depth of the mainshock and 20 aftershocks with Mw > 4. The relocated epicenters cluster in a NW‐SE direction that is consistent with the strike of the mainshock fault plane solution and the slip distribution derived from ALOS‐2 interferometric synthetic aperture radar observations. Most of the aftershocks have a pure thrust focal mechanism similar to the mainshock, except for four strike‐slip aftershocks. The refined locations and moment tensors of the thrust events clearly delineate a fault dipping ∼40° to the southwest at a depth range of 3–7 km, indicating that the earthquake sequence ruptured a previously unmapped, active fault. We interpret the earthquake sequence to be associated with pre‐existing faults within the BYR anticlinorium. This earthquake sequence and historical seismicity indicate that the upper crust of the BYR is highly stressed, resulting in ongoing distributed deformation between the oblique Rakhine megathrust and the dextral Sagaing Fault. The seismic hazard posed by these active faults has been increasing with the development of infrastructure such as dams within the BYR. Our study highlights the need for high‐resolution earthquake source parameter and strong ground motion attenuation studies for further understanding of the neotectonics of Myanmar and its related seismic hazard.
Highlights
Myanmar is situated within a region of active tectonic blocks with boundaries defined by a variety of tectonic settings (Figure 1a)
From the relocation of the earthquake sequence and waveform inversion for the focal mechanism and centroid depth of the mainshock and 20 Mw > 4 afterhocks, we propose that the mainshock ruptured a SW-dipping thrust fault at depth of 3–7 km and possibly triggered a cluster of strike-slip aftershocks at
We suggest that the 2018 Mw 6.0 earthquake is a result of the NESW shortening being partly accommodated by a shallow thrust fault within the Bago-Yoma Range (BYR), while the remaining deformation should be distributed on other secondary faults, such as the West Bago Yoma Fault, Paungde Fault and other unmapped faults, the slip-rate of these faults are not yet known
Summary
Myanmar is situated within a region of active tectonic blocks with boundaries defined by a variety of tectonic settings (Figure 1a). The Burma sliver plate is characterized by the highly oblique convergence of the Indian plate (∼18 mm/yr) at its western boundary while the ∼N–S striking right-lateral Sagaing Fault (∼20 mm/ yr) defines its eastern boundary bordering the Shan Plateau on the Sunda plate The seismicity in Myanmar is highly active, with most of the historical seismicity distributed along the plate-boundary-type Sagaing Fault, the Rakhine subduction zone, and within the subducting Indian slab (Figure 1b). A majority of the seismological and geological studies in the region have been focused on active structures associated with the subduction zone and the Sagaing Fault P. Chen & Molnar, 1990; Le Dain et al, 1984; Ni et al, 1989; Shyu et al, 2018; Steckler et al, 2008; Y. Wang et al, 2013)
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