SLOPE STABILITY AFTER THE 8TH OCTOBER 2005 EARTHQUAKE IN KASHMIR

The Mw=7.6 Kashmir Earthquake occurred 03:50:38UT on 8th October 2005 as a result of rupture on the NW-SE orientated Muzaffarabad Fault. The hypocenter was located at a depth of about 20 km about 19 km NE of Muzaffarabad in the Neelum River valley. The fault rupture extends for a total distance of about 200 km. The earthquake resulted in widespread destruction over 28,000 km2. The official death toll is 87,300, with landslides being responsible for about 20,000 fatalities. Field assessments conducted by the research team in 2006, demonstrated that although large numbers of landslides occurred, the total is substantially less than would be expected for an earthquake of this size based on the relationships of Keefer (1984, 2002). However, many other slopes have sustained high levels of strain, as indicated by extensive networks of tension cracks, arcuate back scarps and lateral scarps. Over the course of the last year increased evidence has been obtained that these damaged slopes have continued to move and a few have failed since the earthquake. In May, over 110 peoples were killed in two small landslides that partially buried two villages and on average ten people per week are being killed by landslides on the roads in the Neelum and Jhelum valleys. Many communities are reporting on-going damage to infrastructure from slope movements causing the authorities to seek to relocate them. During 2006 there were few major failures likely because of the exceptionally dry conditions that prevailed prior to the earthquake, as well as a light monsoon which led to low pore pressures. The situation in 2007 is very different due to a wet winter resulting in elevated pore pressures prior to onset of the monsoon. These conditions increase the risk of failure on many slopes. Using visible imaging to track markers placed on selected seismically disturbed slopes their behavior is being characterized and used to test a model progression from a metastable condition characterized by complex surface movement towards a stable condition characterized by reduced surface movement via a progressive reduction of elevation moderated by factors including compaction, rain infiltration, freeze-thaw cycles, and land use.