SPATIAL DISTRIBUTION OF SEISMIC LANDSLIDES AND THEIR EROSION THICKNESS IN SUBDUCTION ZONE ASSOCIATED WITH SHEAR-THRUST EARTHQUAKE FAULTING MODE

Many landslides were triggered by Haiti Earthquake(Mw 7.0) of January 12, 2010.Base on Geographic Information Systems(GIS) and remote sensing technologies, three detailed landslide inventories were constructed. The three inventories are respectively landslide polygons, landside centroid points, and landslide top points. It is indicated that 30, 828 landslides triggered by the Haiti earthquake throughout the site with area of 3, 192.85km2.These landslides cover a total area of 15.736km2.Correlations of landslide occurrence with seismic parameters, topographic conditions and distance from roads are analyzed using the three landslide inventories. Statistical analysis of these landslides spatial distribution is carried out with four indices. They are a) landslide centroid number density(LCND),defined as the number of landslide centroid per square kilometer, b)landslide top number density(LTND),defined as the number of landslide top point per square kilometer, c)landslide area percentage(LAP),defined as the percentage of the area affected by the landslides, and d) landslide erosion thickness(LET),defined as the landslide material thickness per square kilometer. It is to determine how the occurrence of landslides and their erosion thickness correlates with seismic parameters, topographic conditions and distance from roads. It is observed that values of four indices(LCND,LTND,LAP and LET)have generally positive correlations with slope angle and peak ground acceleration(PGA), and have generally negative correlations with distance from the Enriquillo-Plantain Garden fault, and distance from drainages. Statistical results of landslide and their erosion thickness with distance along the Enriquillo-Plantain Garden fault show that areas from 22 to 26km and 8 to 12km, western of the epicenter, and from 6 to 18km, eastern of the epicenter are landslide high susceptibility areas. It also represents more slope curvature close to zero, more difficult to earthquake triggered landslide occurrence. The highest values appear at range from 200m to 1200m in elevation. The landslides have preferred orientation dominated by the eastern. No apparent correlations were found in the LCND,LTND,LAP and LET values with distance from epicenter and distance from roads.