Ground Motions Due to Large Magnitude Subduction Zone Earthquakes

摘要

The notion that the Cascadia subduction zone (CSZ) has produced very large211u001eearthquakes in the past, and that it can be expected to produce very large 211u001eearthquakes again, is now widely accepted in the seismological and engineering 211u001ecommunities. Rock outcrop motions were sumulated for three CSZ earthquake 211u001escenarios: magnitude 8.0, 8.5, and 9.0 earthquakes. The magnitude 8.0 earthquake 211u001ewas assumed to result from rupture of the portion of the CSZ adjacent to the 211u001enorthern part of the state; the larger magnitude earthquakes were associated with 211u001erupture on a portion of the CSZ extending along the entire length of the state. 211u001eThirty different simulations of each earthquake scenario were analyzed. For each, 211u001erock outcrop motions were computed at each of 13 locations within Washington 211u001estate. Site response analyses were then performed for 15 soil profiles at the 13 211u001elocations. The rock outcrop motions showed amplitudes, frequency contents, and 211u001eduratons that were significantly different than the ground motions that civil 211u001estructures are commonly designed for in Washington state. The durations of CSZ 211u001eground motions are much longer than those of the uotions on which current design 211u001eprocedures are based.