Causative Mechanism of the January 2018 m 6.0 Bago Yoma Earthquake and a New Insight into the Nature of Bago Yoma Mountain Building in Myanmar

The 2000 km long, and approximately 200 km wide elongated tectonic zone in Myanmar has been wedged between the northward moving India plate on the west and southeasterly extruding Indochina plate on the east. The tectonic setting between these moving rigid plates and the highly oblique subduction of the India oceanic plate beneath the Burma continental plate has caused extension to occur on the ductile crust. In turn, this has caused the brittle continental crust to be pulled apart laterally, forming a rift zone. The Central Myanmar Basin has a classic continental rift structures that are arranged in basin-and-uplift configuration in N-S direction. The Bago Yoma is a prominent feature in the Central Myanmar Basin, developed by the basin inversion tectonics due to a change from the extensional regime to compressional regime in Pleistocene to Recent. The Bago Yoma is driven mainly by crustal shortening and uplift, squeezed upward between the Sagaing fault on the east and the Bago fault, Taikkyi fault and Shwepantaw fault on the west. It was formed when linkages among faults have cut through the Bago basin forming Bago Yoma by transpressional push-up and basin inversion in late Tertiary. A strong earthquake of 11th January 2018 occurred at 39 km WSW of Phyu. The magnitude of this earthquake is 6.0, with focal mechanism solution of oblique reverse faulting at the depth of 10 km (USGS). The epicentral location is at latitude 18.363°N- longitude 96.080°E, 39 km WSW of Phyu in the Bago Yoma mountains, Central Myanmar. The main shock was followed by at least six aftershocks with M 5.3, M 5.2, 5.0, 4.8, M 4.6, M 4.3 in the vicinity of epicentral location. The distribution of aftershocks defines a 70-km-wide WNW-ESE-trending weak zone across the Bago-Yoma.