According to the US Geological Survey,
"Liquefaction takes place when loosely packed,
water-logged sediments at or near the ground surface lose their strength in
response to strong ground shaking. Liquefaction occurring beneath buildings and
other structures can cause major damage during earthquakes."
This map visualizes areas of Long
Beach that have either experienced the effects of liquefaction in the past or
where geographic and geological factors "indicate a potential for
permanent ground displacements."