State Geologist Comments on Article

Your Feb. 20 article, “State’s Quake Threat Finding Criticized,” outlines some preliminary staff recommendations that are being prepared for my consideration regarding the recency of fault movement on the Malibu Coast Fault. As California state geologist, I am charged with the responsibility of issuing the final Alquist-Priolo special studies zones maps that are used by local governments to avoid approving locations of structures for human occupancy on active fault traces where they could be damaged.

The article quotes a number of people who disagree with the preliminary recommendations as they understand them. Several individuals suggest that the preliminary recommendations have been influenced by political pressure. I have three observations that I wish to share with your readers:

- There has been no political pressure brought to bear on me or my staff that would alter our geologic conclusions. The final mapping decisions will be made on the basis of geology, not politics.

- The people who were interviewed commented on the preliminary recommendations as they were outlined in the article. This account does not reflect the current status of our staff work on the Alquist-Priolo maps. There will be an opportunity for public commentary between the time that the preliminary maps are officially released and the time the final maps are issued.

- The Alquist-Priolo special studies maps delineate the hazards of ground rupture that relate to fault movements at the land surface. Some of those interviewed feel that the hazard maps should also address damage potential from earthquake shaking and the effects of special site conditions such as liquefaction. These hazards are beyond the authority of the Alquist-Priolo law, and it would be impractical to show them on the active fault maps. A new state earthquake hazards mapping program was authorized by legislation in 1990 and the Department of Conservation’s Division of Mines and Geology is beginning to address liquefaction, earthquake-induced landsliding and amplification of strong ground-motion hazards on a statewide basis. The rate that this new work can proceed will depend upon available funding.

JAMES F. DAVIS

State Geologist

Sacramento