What is liquefaction?

The Gold Rush and the 1906 Earthquake: How they combined to create the breakthrough discovery of modern seismic science

• Accidents of Gold Rush merchant marine navigation transformed a seismic disaster into a seminal discovery and led to San Francisco's extreme liquefaction vulnerability today.
• Just about everything that we love about the Bay area is

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Ground shaking triggered liquefaction in a subsurface layer of sand, producing differential lateral and vertical movement in a overlying carapace of unliquified sand and silt, which moved from right to left toward the Pajaro River. This mode of ground failure, termed "lateral spreading," is a principal cause of liquefaction-related earthquake damage.

"Sand boil" or sand volcano measuring 2 m (6.6 ft) in length erupted in median of Interstate Highway 80 west of the Bay Bridge toll plaza when ground shaking transformed loose water-saturated deposit of subsurface sand into a sand-water slurry (liquefaction). Vented sand contains-marine shell fragments.

Liquefaction in recent deposits of the Pajaro River formed sand volcanoes along a fissure 6-7 m (19.7-23 ft) long. Variation in grain size and partial erosion of the conical deposits of sand show that venting of the slurry of sand and water was a complex series of depositional and erosional events triggered by the main shock and renewed in some instances by principal

Liquefaction in recent deposits of the Pajaro River formed these sand volcanoes along extensional fissures in a field prepared for autumn planting near Pajaro, across the Pajaro River from Watsonville. Furrows are spaced about 1.2 m (4 ft) apart.

Liquefaction in recent deposits of San Lorenzo River caused cracking and differential settling of river levee southeast of Riverside Avenue Bridge. Bridge piers and the north abutment area were also damaged by liquefaction.