Joint Passive/Controlled Source Seismic Experiment Across Taiwan

Scientists who study Earth structures and interactions at tectonic plate boundaries illuminate the three‐dimensional (3‐D) subsurface primarily through passive or active source seismic studies. In passive source studies, natural earthquakes are observed through arrays of seismic stations, allowing seismologists to image structures at depth and infer physical properties of the Earth. In active (controlled) source studies, scientists provide an artificial seismic source to be recorded by seismic networks, allowing more detailed views of fine‐scale structures buried within plate boundaries. The use of “continuous” modes on large‐storage‐capacity seismic recording systems enables seismologists to blur traditional lines between active and passive source seismology in regions of high earthquake activity. In addition to generating seismograms from controlled sources, a deployed dense array can record local and teleseismic earthquakes with exceptionally coherent signals across its aperture. As a result of such joint recording, the scientific value of the collected data increases. Moreover, whether or not the seismic sources are natural or engineered becomes less of a factor for data storage, sorting, and analysis methods. Local earthquakes can supplement controlled sources, multichannel processing and imaging methods traditionally used in active seismic studies become amenable to dense sets of passive source data, and active source data with known source origin times and locations are easily incorporated into regional seismic 3‐D tomography and earthquake location studies.