Permanent upper plate deformation in western Myanmar during the great 1762 earthquake : implications for neotectonic behavior of the northern Sunda megathrust
Shyu, J. Bruce H.
Lin, Yu-nung Nina
Lin, Kyaw Kyaw
Tun, Soe Thura
Date of Issue2013
Earth Observatory of Singapore
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.
DRNTU::Science::Geology::Volcanoes and earthquakes
Journal of geophysical research : solid earth
© 2013 American Geophysical Union. This paper was published in Journal of Geophysical Research: Solid Earth and is made available as an electronic reprint (preprint) with permission of American Geophysical Union. The paper can be found at the following official DOI: [http://dx.doi.org/10.1002/jgrb.50121]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.