Collecting Deep Seismic Data in Densely Populated Vietnam
 The Red River shear zone (RRSZ) is a large-scale strike-slip feature, similar to California's San Andreas Fault system, that extends from Tibet to the South China Sea. Many believe that this fault system allowed Southeast Asia to extrude from Asia as the Indian subcontinent collided with the continent [e.g., Tapponnier et al., 1982]. However, others believe that the collision resulted in crustal thickening and that strike-slip faults helped to accommodate this thickening. There have been many studies of the tectonics and structural geology of the RRSZ both supporting the extrusion hypotheses [e.g., Leloup et al., 1995; Gilley et al., 2003] and challenging them [e.g., Wang and Burchfiel, 1997; Jolivet et al., 2001]. Unfortunately, there have been no crustal reflection or refraction seismic studies of the RRSZ's deep subsurface, data from which might reveal geologic structures indicative of either thickening or extrusion, helping to settle this debate.
The experiment was accomplished with funding from the Vietnam Science Projects (KC.08.06/06-10 and 105.01.24.09) and with field instrument support from the Incorporated Research Institutions for Seismology (IRIS)/Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL), United States. We thank the following participants from Vietnam: Viet-Bac Trinh, Nang-Vu Pham, Van-Tuyen Doan, Hop-Phong Lai, Anh-Vu Tran, Thihong-Quang Nguyen, and other researchers at Vietnam's Institute of Geological Sciences.