[SSS13-P18] The first research on seismic interferometry in the region of induced earthquakes of Song Tranh Dam, Vietnam
Keywords:Seismic Interferometry, Song Tranh Dam, Ambient Noise Tomography
Vietnam is located in South East Asia and bounded by the Pacific and Mediterranean-Himalaya seismic belts on its eastern, western and southern sides, respectively. The dynamic tectonic processes in this region cause the territory of Vietnam and adjacent areas to have intensive differential movement, making the regional tectonic structure very complicated. The tectonics have led this territory to have moderate seismic activity and complicated geological structures, such as the Lai Chau-Dien Bien fault zone, Red River fault zone, and others. Southern Vietnam was considered to be a region with low seismicity, compared to the North. However, the sequence of earthquakes that occurred at Song Tranh Dam during the last several years surprised many scientists because the southern region of Vietnam was not expected to have major tectonic activity. This region where many induced earthquakes are now occurring is associated with the filling of a new reservoir. There have been four M4 earthquakes (maximum earthquake was 4.7 in November, 2012), so it is one of the most active induced earthquakes examples in the world. It is important to determine the strong motion attenuation relations for this area since damaging earthquakes may be expected in the near future. We collect and process data from 10 seismic stations around Song Tranh dam, include 5 years continued data in Song Tranh dam.
Traditional methods of imaging the Earth’s subsurface using seismic waves require an identifiable, impulsive source of seismic energy, for example an earthquake or explosive source. Naturally occurring, ambient seismic waves form an ever-present source of energy that is conventionally regarded as unusable since it is not impulsive. As such it is generally removed from seismic data and subsequent analysis. A new method known as seismic interferometry can be used to extract useful information about the Earth’s subsurface from the ambient noise wavefield. Consequently, seismic interferometry is an important new tool for exploring areas which are otherwise seismically quiescent, such as the Song Tranh Dam region in which there are relatively thousands of induced earthquakes. Here we provide a review of seismic interferometry and show that the seismic interferometry method which have agreeable results within the Song Tranh dam region.
One of the possible applications of seismic interferometry is ambient noise tomography (ANT). ANT is a way of using interferometry to image subsurface seismic velocity variations using seismic (surface) waves extracted from the background ambient vibrations of the Earth. Today, ANT has been used successfully to image the Earth’s crust and upper-mantle on regional and continental scales in many locations and has the power to resolve major geological features such as sedimentary basins and igneous and metamorphic cores. In future study we will do some advance research on ANT in Song Tranh Dam region and make comparison between Northern and Southern of VietNam (especially Moho layer).
Traditional methods of imaging the Earth’s subsurface using seismic waves require an identifiable, impulsive source of seismic energy, for example an earthquake or explosive source. Naturally occurring, ambient seismic waves form an ever-present source of energy that is conventionally regarded as unusable since it is not impulsive. As such it is generally removed from seismic data and subsequent analysis. A new method known as seismic interferometry can be used to extract useful information about the Earth’s subsurface from the ambient noise wavefield. Consequently, seismic interferometry is an important new tool for exploring areas which are otherwise seismically quiescent, such as the Song Tranh Dam region in which there are relatively thousands of induced earthquakes. Here we provide a review of seismic interferometry and show that the seismic interferometry method which have agreeable results within the Song Tranh dam region.
One of the possible applications of seismic interferometry is ambient noise tomography (ANT). ANT is a way of using interferometry to image subsurface seismic velocity variations using seismic (surface) waves extracted from the background ambient vibrations of the Earth. Today, ANT has been used successfully to image the Earth’s crust and upper-mantle on regional and continental scales in many locations and has the power to resolve major geological features such as sedimentary basins and igneous and metamorphic cores. In future study we will do some advance research on ANT in Song Tranh Dam region and make comparison between Northern and Southern of VietNam (especially Moho layer).