LOS ANGELES is moving again—but this time earthquakes are not to blame.
Groundwater being pumped by the city authorities is causing deformations up to
five times as large as the seismic movements monitored by geologists.
Researchers from the US Geological Survey first identified the problem in a
network of 250 seismic stations it set up in the Los Angeles basin after the
1987 and 1994 earthquakes. Position data from some stations showed unexpected
movements.
To trace their origins, Gerald Bawden of USGS compared a series of elevation
profiles compiled by satellite-based radar at different times. He found that a…
