Landslides and other ground damage caused by the M_W7.2 Fiordland earthquake of 22 August 2003

摘要

The M_W 7.2 Fiordland earthquake of 22 August 2003 was located -75 km northwest of Te Anau. It was the largest earthquake in New Zealand for 35 years, and involved thrusting on the subduction interface zone, not the Alpine Fault. Because of its location in an unpopulated area the earthquake caused only minor damage to buildings and infrastructure, but produced widespread superficial landsliding on steep slopes over more than 3000 km~2 west of Te Anau. More than 400 landslides with volumes up to -700,000 m~3 occurred during the earthquake, principally on very steep slopes within 25 km of the underlying earthquake fault plane where shaking intensity is estimated to have reached MM IX. Minor liquefaction effects (sand boils and lateral spreading) were observed in saturated sandy alluvium in many places. There were no very large bedrock failures similarto the very large (～10~7-10~9 m~3) prehistoric landslides previously identified in Fiordland.