Historic Earthquakes

San Jacinto, California
1918 April 21 22:32:25 UTC
Magnitude 6.8

Major damage occurred in San Jacinto, about 120 km southeast of Los Angeles and at Hemet, about 3 km south of San Jacinto. Several residents were injured, and one was killed. An earthquake of similar intensity occurred in the same area on December 25, 1899.

In the business section of San Jacinto, a town of about 1,000 population, only one new concrete building and one frame building remained standing after the earthquake. Most of the ruined buildings were of poor construction, however. Property damage at Hemet was not as severe as in San Jacinto. No buildings were wrecked, and no buildings of good construction were damaged seriously. Total property loss in the two towns was estimated at $200,000.

Light damage to structures occurred in several towns within a 160-km radius of San Jacinto. Concrete irrigation canals were broken in several places in the Hemet-San Jacinto area.

Many lengthwise cracks were observed in the highway between San Jacinto and Hemet, but cracks were not observed at the sides of this highway. About 1.5 km from the center of San Jacinto, the concrete highway was buckled, and a section about 1 meter wide was torn up. Cracks in the ground were noted in four areas, but all were believed to be due to the shaking, not to the surface rupture along the San Jacinto fault. Many small sand craters were observed on a farm about 1.5 km northwest of San Jacinto. Felt from Taft (Kern County) in the north along the coast to San Diego (and probably into Mexico) and from Needles (San Bernardino County) in the east, south to Yuma, Arizona. Many aftershocks occurred, including a strong tremor on June 6, 1918. Two moderate shocks on April 22 (16 07 and 16 14 UTC) shook down loose bricks and tottering walls in Hemet and San Jacinto.

Abridged from Seismicity of the United States, 1568-1989 (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993.