Official Time of Earthquake
From "California Geology" January 1990

Most people in the vicinity of the earthquake epicenter felt strong ground shaking for about 10 to 15 seconds. People felt the effects of the P wave first, then the strong shaking associated with the S waves. P waves travel at speeds of about 3.1 - 3.7 miles per second through average crustal materials, whereas S waves travel more slowly, about 2.0 miles per second. Therefore, people in San Francisco (56 miles) felt the earthquake about 23 seconds later than the people in Santa Cruz (10 miles) and people in Sacramento (100 miles) felt it about 22 seconds later."

Strong Motion recorder at Corralitos - Eureka Canyon Road, near the epicenter, recorded the earthquake beginning at 5:04:21 p.m.

The first quake wave arrived one second later at the Fire Station in Capitola.

The first wave began to shake the water tank at Gavilan College in Gilroy at 5:04:24 p.m.

Strong motion instruments at the Pulgas Water Temple at Upper Crystal Springs Reservoir recorded the quake beginning at 5:04:31 p.m.

Sierra Point Freeway overpass monitor, nearest to Candlestick Park, recorded the quake at 5:04:34 p.m.

The quake wave arrived at the Presidio of San Francisco, nearest the Marina District, at 5:04:37 with the heaviest shaking recorded at 5:04:47 p.m.

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