Lessons learned and need for instrumented liquefaction sites

Instrumented sites provide essential information for understanding and modeling of ground response and ground deformation. For example, significant new lessons were learned from responses at the Wildlife Liquefaction Array (WLA) including: (1) soil softening led to lengthening of period of transmitted ground motions; (2) soil softening also led to attenuation of short-period spectral accelerations (<0.7 s); (3) amplification of long period motions (>0.7 s) occurred due to liquefaction-induced ground oscillation; and (4) ground oscillation led to a continued rise of pore water pressures after strong ground shaking ceased. A new and expanded instrumented site is being developed 70 m downstream from the old WLA site as part of the NSF Network for Earthquake Engineering Simulation (NEES). The new site has more accelerometers, piezometers and ground deformation measurement devices and the data will be streamed to the NEES-grid in near real time.