NS acceleration at ground surface and 7.5 m depth
The Wildlife site (Imperial County, Calif) data recorded during the Superstition Hills earthquake [05:15 Pacific Standard Time (PST), November 24, 1987] are currently unique in the United States, if not worldwide. During this event, the site response was monitored by a surface and a downhole strong motion instrument, as well as by six pore-water pressure transducers. Field investigations after the earthquake provided evidence of liquefaction and minor permanent lateral ground displacement (Holzer et al. 1989).
Accelerations were recorded in the north-south (NS) and east-west (EW) directions at ground surface and 7.5 m depth. Excess pore-pressures were recorded by piezometers P1-P6. A recent in situ effort to calibrate the piezometers showed that the P5 pore-pressure transducer responded consistently similar to an employed reference transducer (Hushmand et al. 1991, 1992). More detailed discussions concerning instrumentation performance are reported by Hushmand et al. (1991, 1992) and Youd and Holzer (1993). The surface records displayed some peculiar acceleration spikes associated with simultaneous pore-pressure drops.
NS acceleration at ground surface and 7.5 m depth
Excess pore-water pressure measured by P5 (at 2.9 m depth)