Letters from the August 13, 2005, issue of Science News
By Science News
Bay listen
It was interesting to read of processing mundane noise to produce an ultrasound image of the geology of Los Angeles (“Seismic noise can yield maps of Earth’s crust,” SN: 6/11/05, p. 382). A big question in the state is the deep structure of San Francisco Bay. Clearly, the bay and the valleys extending to its northwest and southeast form a rift valley. But it’s difficult to observe faulting in the rocks because of the depth of sediment. Maybe the area could be probed ultrasonically.