The Loma Prieta, California, Earthquake of October 17, 1989—Hydrologic Disturbances

Seismic events have long been known to cause changes in the level of oceans, streams, lakes, and the water table. The great San Francisco earthquake of 1906 induced significant hydrologic changes that were qualitatively similar to those changes observed for the Loma Prieta earthquake. What is different is that the hydrologic data sets collected from the Loma Prieta event have enough detail to enable hypotheses on the causes for these changes to be tested. The papers in this chapter document changes in ocean level, stream morphology and flow, water table height, and ground-water flow rates in response to the earthquake. Although hydrologic disturbances may have occurred about 1 hour before the main shock, the papers in this chapter deal strictly with postevent hydrologic changes. The hydrologic responses reported here reflect changes that are not the result of surface rupture. They appear to be the result of landslides, the static displacements induced by the earthquake, and changes in the permeability of the near surface.

This publication consists of the following articles:

• Introduction, by Stuart Rojstaczer

• The origin of the tsunami excited by the earthquake-faulting or slumping, by Kuo-Fong Ma, Kenji Satake, and Hiroo Kanamori

• Stream-channel adjustment in Fern Canyon near Watsonville, California, after the earthquake, by Deborah R. Harden and Dennis Fox

• Effects of the earthquake on surface waters in Waddell Valley, by Robert O. Briggs

• Sources and magnitudes of increased streamflow in the Santa Cruz Mountains for the 1990 water year after the earthquake, by Robert R. Curry, Brett A. Emery, and Tom Gentry Kidwell

• Hydrologic changes associated with the earthquake in the San Lorenzo and Pescadero drainage basins, by Stuart Rojstaczer and Stephen Wolf

This publication is part of the set of four multi-chapter USGS Professional Papers on the Loma Prieta, California, Earthquake of October 17, 1989:

Professional Paper 1550, Earthquake Occurrence , Coordinators: William H. Bakun and William H. Prescott

Professional Paper 1551, Strong Ground Motion and Ground Failure, Coordinator: Thomas L. Holzer

Professional Paper 1552, Performance of the Built Environment, Coordinator, Thomas L. Holzer

Professional Paper 1553, Societal Response, Coordinator: Dennis S. Mileti