SEA-FLOOR GAS SEEPS TRIGGERED BY A NORTHERN CALIFORNIA EARTHQUAKE

A series of marine surveys using high-resolution seismic-reflection and side-scan sonar profiling was conducted on the Klamath River delta from 1977 to 1985. In November 1980, near the middle of this 8-year time period, a major earthquake (magnitude 7) occurred in the area. The earthquake caused liquefaction of shelf deposits off the Klamath River, and while mapping the sediment failures, an inordinate number of gas vents and acoustic anomalies in the sediment (gas charging) and water column (gas clouds) was observed. A change in gas seepage occurred after the earthquake. The gas released may have been in part thermogenic in origin.