M6.9 earthquake 27 km NNW of Tachilek, Myanmar

At least 74 people killed, 111 injured, 413 buildings damaged and one bridge collapsed in Shan. Landslides occurred in the area. Felt (VI) at Kengtung and (II) at Rangoon. Also felt at Mandalay and Taunggyi. One person killed in northern Thailand. Felt (VI) at Mae Sai; (IV) at Amnat Charoen, Chiang Rai, Lamphun, Mae Chan, Mae Rim, Nan, Nonthaburi, Phayao and Pong; (III) at Bangkok, Chiang Mai, Hang Dong, Lampang, Mae Hong Son, San Kamphaeng, San Pa Tong and San Sai. Twelve people injured, 9,496 people displaced and 9,691 houses, 136 reservoirs and 35 roads damaged in Yunnan, China. Felt (IV) at Jinghong, (III) at Nanning and (II) at Kunming. Felt (IV) at Louang Namtha and (II) at Louangphabang and Vientiane, Laos. Felt (III) at Hanoi, Vietnam. Also felt at Ho Chi Minh City. Felt widely in Laos, Myanmar, Thailand, Vietnam and southern China. Also felt at Phnom Penh, Cambodia and in Singapore. Felt at Dhaka, Bangladesh and at Aizawl, India.

Present-day deformation and earthquakes in Myanmar and adjacent parts of southeast Asia are driven by the northward movement of the Indian subcontinent as it collides with the Eurasian plate. Myanmar, on the eastern side of this collisional zone, lies east of the boundary between the Indian plate to the west, and the Sunda plate. At the latitude of the March 24 earthquake, the Indian plate moves north-northeast with respect to the Sunda plate at a rate of approximately 45 mm/yr. Most of the differential motion between these two plates in Myanmar is concentrated on the Sagaing fault, which is a major north-striking, right-lateral fault that has a slip rate of approximately 18 mm/yr based on GPS data, and lies almost 400 km west of the March 24 earthquake. Numerous large earthquakes have occurred on the Sagaing fault in the past century, including a M 6.9 event in February 1991, which caused 2 fatalities.

Additional deformation caused by the collision between the Indian and Sunda plates extends to the east across Myanmar and into neighboring Thailand and northern Laos. In northeastern Myanmar, the collision is causing internal deformation in the Shan plateau and the Shan-Thai block, which are cut by a series of northeast-striking, left-lateral faults. These include, from south to north, the Mae Chan, Nam Ma, Menxing, Menglian, Nantinghe, Wanding, and Longling faults. The March 24 M 6.8 earthquake occurred in a region of distributed deformation in the Shan-Thai block. The closest nearby large and damaging earthquake in recent history was an M 6.8 event ~170 km to the north-northeast in July 1995, which caused 11 fatalities.

The focal mechanism of this event, indicating potential left-lateral slip on a northeast-trending nodal plane, is similar to the slip indicated by historical focal mechanisms throughout northeastern Myanmar.