The Morgan Hill Earthquake of April 24, 1984—Investigation of Lifelines

Abstract

The overall response of all lifelines was good although there was some significant damage. In the power system there was significant damage to 500 kV circuit breakers at two substations, some other minor substation damage, and some damage to feeders in the distribution system. The substation damage did put a segment of one of the AC Pacific Interties out of service for a couple of days but the remaining intertie was able to carry the load. The loss of feeder lines caused local disruption of power for up to 5 hours. In water and sewage systems two 8 inch transit water lines broke in Morgan Hill and a break in an 8 inch pipe to a 350,000 gallon tank caused a large water loss. Five 6 inch water line couplings disengaged. There were numerous water service connection failures in the high damage area. There was no significant damage to communication systems but there was a significant downgrade in the quality of service due to system overload. Calls from outside the area were limited by AT&T. Damage to highway systems was limited to that caused by a rock slide which blocked E. Dunne Avenue near the Anderson Reservoir and damaged a nearby bridge over the reservoir. One bridge span moved one foot near an abutment and caused the adjacent pier to move out of plumb by almost one foot. The road surface on the crest of the Anderson Dam was cracked but there was no damage to the dam. In the natural gas system there was no damage to the utilities part of the system. A large fire in San Jose was caused by a gas leak in piping to a gas fired industrial heater. There was an explosion and fire in a mobile home and numerous leaks associated with toppled water heaters. There were numerous leaks beyond service connections to homes in the high damage area.