Paleoearthquakes along Xaignabouli Fault Zone in Western Lao PDR
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Abstract
A paleoseismic investigation has been carried out to identify the faults at the Xaignabouli (XYB) area in western Lao PDR to determine if they are seismologically and geologically active. There have been earthquakes of intermediate magnitudes reported recently (5.4 and 3.9 ML in February and March 2011, respectively) suggesting that the area is seismologically active. Our remote-sensing data show that these two earthquakes may have been related to the northeast-southwest trending fault. Regionally, the fault commenced in the north from Dien Bien Phu (DBP) in Vietnam. Lineaments analysis using SRTM DEM image data together with epicentral distribution suggest that there are not only northeast-southwest trending lineaments but also those of the northwest-southeast and northsouth strikes. Our interpretation and synthesis using geological, present-day seismicity, seismotectonic, and paleoseismological data reveal that there are at least two active strike-slip fault zones with sinistral movement and these faults are branches of the DBP fault. The first fault zone passes the western part of the XYB and is oriented in the NE-SW direction and comprised of about 20 segments ranging from 10 km up to 110 km with a total length of about 450 km. The second is almost subparallel to first and has a total length of 350 km also consisting of shorter segments. Results of morphotectonic features and Quaternary age dating imply horizontal slip rate at ca. 0.8 mm/yr. The main northeast-southwest trending fault is estimated at about 16.8 km east of the XYB area. Our study reveals that the area has been subject to multiple tectonic phases of deformation, with the most essential episode occurring during late Cenozoic time. OSL dating result indicates that three earthquake faulting events ca. 3,000, 2,000, and 1,000 years ago support a recurrence interval of approximately 1,000 years. Surface rupture length indicates maximum credible earthquake magnitudes between 5.6 and 7.3 Richter.
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Copyright © 2008 Department of Geology, Faculty of Science, Chulalongkorn University. Parts of an article can be photocopied or reproduced without prior written permission from the author(s), but due acknowledgments should be stated or cited accordingly.
References
Charusiri, P., Daorerk, V., Archibald, D., Hisada, K. and Ampaiwan, T. 2002. Geotectonic evolution of Thailand: a new synthesis. Journal of the Geological Society of Thailand 1: pp.1-20.
Hutchison, C.S. 1989. Geological Evolution of South-East Asia, Oxford University Press, England, pp.368.
Pailoplee, S., Sugiyama, Y., and Charusiri, P. 2009. Deterministic and probabilistic seismic hazard analyses in Thailand and adjacent areas using active fault data. Earth, Planets and Space 61: 1313–1325.
Nguyen, V. H. and Hoang, Q.V. 2001. Moving characteristics of the Lai Chau–Dien Bien Fault zone during Cenozoic, Journal of Geology, Series B, No. 17–18, p. 65–77.
Peltzer G and P Tapponnier. 1988. Formation and evolution of strike-slip faults, rifts, and basins during the India-Asia Collision: an experimental approach. Journal of Geophysical Research 93: pp.15085-15117
Polachan, S., Pradidtan, S., Tongtaow, C., Janmaha, S., Intrawijitr, K., and Sangsuwan, C. 1991. Development of Cenozoic basins in Thailand. Marine and Petroleum Geology 8: pp.84–97.
Tapponnier, P., Peltzer, G., Armijo, R., Le Dain, A.-Y., and Cobbold, P., 1982 Propagating extrusion tectonics in Asia: New insights from simple experiments with plasticine. Geology 10, pp. 611–616.
Trinh, P.T., Lacassin, R., Tapponnier, P., Leloup, P.H., Yem, N.T., 1993. Evidence for active strike-slip movements in Northwestern Vietnam. Terra Abstracts, Suppl. 1 to Terra Nova 5, 265.
Trinh, P.T., et al., 1999. Active tectonics and seismic hazard in Son La hydropower dam (North Vietnam). J. Geol., Ser. B (Hanoi) 13– 14, 19– 32.
Tien, P.C., et al., 1991. Geological map of Cambodia, Laos, and Vietnam, 1:1,000,000. The Geological Survey of Vietnam, Hanoi.
Trieu, C.D., Xuan, N.T., Thang, N.C., Dung, L.V., Tuyen, N.H., 1999. Seismic hazard assessment in Tay Bac region, Vietnam. J. Geol., Ser. B (Hanoi) 13– 14, 163–173.
Wells, D.L., and Coppersmith, K.J. 1994. Updated empirical relationships among magnitude, rupture length, rupture area, and surface displacement. Bulletin of the Seismological Society of America 84: 974–1002.
Zuchiewicz, W., Cuong, N.Q., Bluszcz, A., Michalik, A., 2004. Quaternary sediments in the Dien Bien Phu fault zone, NW Vietnam: a record of young tectonic processes in the light of OSL-SAR dating results. Geomorphology 60; 269–302.