Mapping the macroseismic effects of the MW 6.8 Thabeikkyin earthquake in 2012, upper Myanmar

Abstract:

In 2012, the Mw 6.8 Thabeikkyin earthquake along the northern Sagaing fault devastated residential and public structures in the Myanmar. The earthquake killed 26 people, and left 12 missing and 231 injured in the epicentral region. In addition, 201 houses, 25 schools, 13 hospitals, 35 monasteries, and 45 pagodas totally collapsed or were partially damaged in upper Myanmar. The USGS’s instrumental epicenter was near the Male fault, a western splay of the major Sagaing fault, with a shallow focal depth of ~9.8 km. Our post-earthquake field survey documented a ~45 km long surface rupture with ~1.02 m maximum dextral offset on the main fault, between Singu town in the south, passing through Thabeikkyin town, and terminating in Sabenago village in the north. The present study clarifies the macroseismic felt intensity of the Thabeikkyin earthquake in the EMS-98 scale, emphasizing the damage pattern and macroseimic effects in Myanmar and surrounding regions, based on press reports, digital news, and post-earthquake field survey data. In the epicentral region, the macroseismic intensity reached EMS 7-8, corresponding to grade 3 to grade 4 damage along the surface rupture. Light to moderate damage, corresponding to EMS 5-6 was distributed between the latitudes of Tagaung and Myittha towns in central Myanmar. Ground shaking during the Thabeikkyin earthquake was also reported from Yangon and Bhamo cities in Myanmar and light shaking was widely felt in the Assam region of India, in Kunming in western China and, in Chaing Mai and Bangkok in Thailand. High macroseismic intensities extend more widespread in the NE-SW direction than the NW-SE direction. Our study suggests that the peak distribution of felt intensity corresponds to the dilation fields of the USGS mainshock focal mechanism.