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Hydrologic effects associated with the June 28, 1992 Landers, California, earthquake sequence

1995; United States Department of the Interior; Linguagem: Inglês

10.3133/ofr9542

2332-4899

Evelyn Roeloffs, Wesley R. Danskin, Christopher D. Farrar, Devin L. Galloway, S.N. Hamlin, E.G. Quilty, H.M. Quinn, D.H. Schaefer, M.L. Sorey, Douglas Woodcock,

Seismic Waves and Analysis

This report compiles hydrologic observations in southern California and elsewhere associated with the 1992 ML = 7.3 Landers, California earthquake sequence.In southern California, the largest ground-water-level changes were a rise of 3 meters at Lucerne Valley and a drop of 5 m at Pinon Flat.Most of the steplike water-level changes recorded in the hours following the Landers and Big Bear earthquakes agreed in direction with the sign of the calculated coseismic volume strain field.In the Pinon Flat area, however, two wells measured on June 28, after both these earthquakes, displayed water-level rises of 9 cm above the reading made two days before.A spring discharge increase in Millard Canyon was reported to have preceded the earthquake by several days.Outside of southern California, water-level changes were also observed, but are not consistent in sign or size with the static strain field of the earthquake sequence.At Parkfield, California, water-level changes took place in three wells at the time of the earthquake, and recovered over periods as long as 30 days.At Long Valley, California, observed water-level changes generally returned to normal after minutes to hours, consistent with their having been caused by the passage of surface waves.Water levels in one well at Long Valley and in a well near Grants Pass, Oregon, remained low for at least two days following the earthquake.Water-level oscillations took place in two wells in eastern Nevada.Phenomena accompanying the Landers earthquake that were of practical significance include the Tapo Canyon oil seep, which polluted part of the Santa Clara River; gas bubbles in San Bernardino city water supply wells, which clogged filters; and a coseismic discharge increase in Millard Creek, which added to the water supply.1. Includes response to Big Bear earthquake.