Active tectonics at the piedmont of a growing mountain belt in relation to recent seismicity and orogeny: The example of Southern Taiwan
About the Event:
The piedmonts and foreland basins of active mountain belts commonly concentrate human population, fertile land and industries. They are also the location of seismogenic faults that expose the population and economic activities to significant seismic hazard that active tectonics studies aim at better quantifying.
This seminar will focus on the active geological structures of the foothills of southern Taiwan that host about 5 million inhabitants. The island of Taiwan lies on the circum-Pacific Ring of Fire, at the junction between the Ryukyu Trench and the Manilla Trench. The mountain belt results from the collision at a fast rate of 8 cm/yr between the Luzon volcanic arc on the Philippine Sea Plate and the Chinese passive continental margin on the Eurasian Plate. In southern Taiwan, about half the plate rate is consumed across the western piedmont and the Coastal Plain, yet the active structures that accommodate shortening remain poorly documented. A Mw6.4 earthquake stroke the area in 2016, causing over 110 casualties in buildings collapse and emphasizing the need for further active fault investigations in the area.
In this talk, I will show how we constrain the location, geometry and, when possible, the kinematics of the active faults and folds at the front of the mountain belt at the latitude of the 2016 earthquake. This study combines multidisciplinary tools: geodesy during the interseismic and coseismic periods, geomorphology, shallow and deep boreholes, seismic reflection profiles, balanced geological cross-sections, and chronological constraints based on published nannostratigraphy and magnetostratigraphy. These results will be discussed together with recent seismicity and orogeny thanks to tomography at the scale of the mountain belt.
About the Speaker:
Maryline Le Béon specialises in active tectonics in strike-slip and contractional settings in relation to seismic hazard assessment and in Quaternary geochronology. She received her Master degree in 2004 and her Ph.D. degree in 2008 from the Tectonics Laboratory of the Institut de Physique du Globe de Paris, France, working on paleoseismology and fault slip rates on the strike-slip Dead Sea Fault, in Lebanon and Jordan. In 2008, she moved to Taiwan as a post-doctoral researcher. She worked at National Taiwan University, Academia Sinica and National Central University where she still locates today. In Taiwan, Maryline gained experience with active folds and thrusts, connecting deformation at the land surface and active geological structures in the sub-surface. She also trained herself to Luminescence dating and started challenging Quaternary-dating techniques by applying different chronometers on the same sedimentary deposits. In 2015, Maryline obtained a 3-year research grant from the Taiwan Ministry of Science and Technology to work on active tectonics in southwestern Taiwan.