This paper describes geomorphologic evidence for the principal neotectonic features of Myanmar and its immediate surroundings. We combine this evidence with published structural, geodetic, and seismic data to present an overview of the active tectonic architecture of the region and its seismic potential. Three tectonic systems accommodate oblique collision of the Indian plate with Southeast Asia and extrusion of Asian territory around the eastern syntaxis of the Himalayan mountain range. Subduction and collision associated with the Sunda megathrust beneath and within the Indoburman range and Naga Hills accommodate most of the shortening across the transpressional plate boundary. The Sagaing fault system is the predominant locus of dextral motion associated with the northward translation of India. Left-lateral faults of the northern Shan Plateau, northern Laos, Thailand, and southern China facilitate extrusion of rocks around the eastern syntaxis of the Himalaya. All of these systems have produced major earthquakes within recorded history and continue to present major seismic hazards in the region.
Primate dental and postcranial remains from the Eocene Pondaung Formation (Myanmar) have been the subject of considerable confusion since their initial discoveries, and their anthropoid status has been widely debated. We report here a well preserved primate talus discovered in the Segyauk locality near Mogaung that displays derived anatomical features typical of haplorhines, notably anthropoids, and lacks strepsirhine synapomorphies. Linear discriminant and parsimony analyses indicate that the talus from Myanmar is more similar structurally to those of living and extinct anthropoids than to those of adapiforms, and its overall osteological characteristics further point to arboreal quadrupedalism. Regressions of talar dimensions versus body mass in living primates indicate that this foot bone might have belonged to Amphipithecus. This evidence supports hypotheses favoring anthropoid affinities for the large-bodied primates from Pondaung and runs contrary to the hypothesis that Pondaungia and Amphipithecus are strepsirhine adapiforms.talus ͉ anthropoid primates
The 1762 Arakan earthquake resulted from rupture of the northern Sunda megathrust and is one of those rare preinstrumental earthquakes for which early historical accounts document ground deformations. In order to obtain more comprehensive and detailed measurements of coseismic uplift, we conducted comprehensive field investigations and geochronological analyses of marine terraces on the two largest islands in western Myanmar. We confirm 3–4 m of coseismic coastal emergence along southwestern Cheduba Island, diminishing northeastward to less than 1 m. Farther northeast, uplift associated with the earthquake ranges from slightly more than 1 m to 5–6 m along the western coast of Ramree Island but is insignificant along the island's eastern coast. This double‐hump pattern of uplift coincides with the long‐term anticlinal growth of these two islands. Thus, we propose that the 1762 earthquake resulted from slip on splay faults under the islands, in addition to rupture of the megathrust. Elastic modeling implies that fault slip during the 1762 earthquake ranges from about 9 to 16 m beneath the islands and corresponds to a magnitude of Mw 8.5 if the rupture length of the megathrust is ~500 km. The island's uplift histories suggest recurrence intervals of such events of about 500–700 years. Additional detailed paleoseismological studies would add significant additional detail to the history of large earthquakes in this region.
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