Interpretation of landslide distribution triggered by the 2005 Northern Pakistan earthquake using SPOT 5 imagery

Abstract

The 2005 northern Pakistan earthquake (magnitude 7.6) of 8 October 2005 occurred in the northwestern part of the Himalayas. We interpreted landslides triggered by the earthquake using black-and-white 2.5-m-resolution System Pour l'Observation de la Terre 5 (SPOT 5) stereo images. As a result, the counts of 2,424 landslides were identified in the study area of 55 by 51 km. About 79% or 1,925 of the landslides were small (less than 0.5 ha in area), whereas 207 of the landslides (about 9%) were large (1 ha and more in area). Judging from our field survey, most of the small landslides are shallow rock falls and slides. However, the resolution and whitish image in the photos prevented interpreting the movement type and geomorphologic features of the landslide sites in detail. It is known that this earthquake took place along preexisting active reverse faults. The landslide distribution was mapped and superimposed on the crustal deformation detected by the environmental satellite/synthetic aperture radar (SAR) data, active faults map, geological map, and shuttle radar topography mission data. The landslide distribution showed the following characteristics: (1) Most of the landslides occurred on the hanging-wall side of the Balakot-Garhi fault; (2) greater than one third of the landslides occurred within 1 km from the active fault; (3) the greatest number of landslides (1,147 counts), landslide density (3.2 counts/km 2 ), and landslide area ratio (2.3 ha/km 2 ) was found within Miocene sandstone and siltstone, Precambrian schist and quartzite, and Eocene and Paleocene limestone and shale, respectively; (4) there was a slight trend that large landslides occurred on vertically convex slopes rather than on concave slopes; furthermore, large landslides occurred on steeper (30°and more) slopes than on gentler slopes; (5) many large landslides occurred on slopes facing S and SW directions, which is consistent with SAR-detected horizontal dominant direction of crustal deformation on the hanging wall.

Landslides and vegetation cover in the 2005 North Pakistan earthquake: a GIS and statistical quantitative approach

“…It also shows that below a slope of 30 • , landslides area may increase when located closer to active fault. This is in line with findings provided by Sato et al (2007).…”

“…Higher resolution DEM might improve the model. It may allow computation of concave and convex slopes as this was proven to be an improved explanatory factor in other study (Sato et al, 2007).…”

“…More than 30% of the victims were killed by landslides (Petley et al, 2006). More than 2400 landslides were identified by remote sensing techniques (Sato et al, 2007) following this earthquake. The biggest individual landslide triggered by the Kashmir Earthquake 2005 was the 68 millions m 3 Hattian Bala rock avalanche that killed about 1000 people (Dunning et al, 2007).…”

“…A remarkable study (Sato et al, 2007) used Synthetic Aperture Radar (SAR) images from ENVISAT revealing a maximum six-meter uplift north of Muzaffarabad. In the same study, landslide detection performed by comparing a pair of pre-and post-event SPOT-5 images plotted over a Digital Elevation Model (DEM).…”

Prediction of the area affected by earthquake-induced landsliding based on seismological parameters

“…These 83 cases have been harvested from published compilations (Keefer, 1984;Hancox et al, 1997;Rodriguez et al, 1999;Bommer and Rodriguez, 2002;Martino et al, 2014) and from recent landslide maps (Table 1). They include the 10 cases with comprehensive landslide inventories described separately below, 36 inventories for which we could access one or several maps with isolines of landslides density or point inventories to check the values reported in published compilations (Bonilla, 1960;Keefer et al, 1980;Harp et al, 1984;Harp and Keefer, 1990;Jibson et al, 1994;Tibaldi et al, 1995;Hancox et al, 1997;Keefer and Manson, 1998;Hancox et al, 2003Hancox et al, , 2004Jibson and Harp, 2006;Mahdavifar et al, 2006;Sato et al, 2007;Kamp et al, 2008;Mosquera-Machado et al, 2009;Alfaro et al, 2012;Collins et al, 2012;Jibson and Harp, 2012;Gorum et al, 2014;Martino et al, 2014;Xu et al, 2014aXu et al, , b, 2015Martha et al, 2016;Zhou et al, 2016), and a further 37 cases for which we could not access any raw data to evaluate the reported values (Table 1). For 10 earthquakes, detailed landslide inventories with comprehensive maps of the landslide as polygons are available, allowing an objective characterization of A d (as discussed below): the 1976 Guatemala, 1991Limon, 1993Finisterre, 1994Northridge, 1999Chi-Chi, 2004…”