Abstract :
[en] Abstract. First analyses of landslide distribution and triggering factors
are presented for the region affected by the 14 August 2021 earthquake
(Mw=7.2) in the Nippes Department, Haiti. Landslide mapping was mainly
carried out by comparing pre- and post-event remote imagery (∼0.5–1 m resolution) available on Google Earth Pro® and
Sentinel-2 (10 m resolution) satellite images. The first covered about
50 % of the affected region (for post-event imagery and before completion
of the map in January 2022), and the latter were selected to cover the entire
potentially affected zone. On the basis of the completed landslide
inventory, comparisons are made with catalogs compiled by others both for
the August 2021 and the January 2010 seismic events, including one open
inventory (by the United States Geological Survey) that was also used for
further statistical analyses. Additionally, we studied the pre-2021
earthquake slope stability conditions. These comparisons show that the total
number of landslides mapped for the 2021 earthquake (7091) is larger than
the one recently published by another research team for the same event but
slightly smaller than the number of landslides mapped by a third research
team. It is also clearly smaller than the one observed by two other research
teams for the 2010 earthquake (e.g., 23 567, for the open inventory).
However, these apparently fewer landslides triggered in 2021 cover much
wider areas of slopes (>80 km2) than those induced by the
2010 event (∼25 km2 – considering the open inventory).
A simple statistical analysis indicates that the lower number of
2021 landslides can be explained by the missing detection of the smallest
landslides triggered in 2021, partly due to the lower-resolution imagery
available for most of the areas affected by the recent earthquake; this is
also confirmed by an inventory completeness analysis based on size–frequency
statistics. The much larger total area of landslides triggered in 2021,
compared to the 2010 earthquake, can be related to different physical
reasons: (a) the larger earthquake magnitude in 2021, (b) the more central
location of the fault segment that ruptured in 2021 with respect to coastal
zones, (c) and possible climatic preconditioning of slope instability in the
2021 affected area. These observations are supported by (1) a new pre-2021
earthquake landslide map; (2) rainfall distribution maps presented for
different periods (including October 2016 – when Hurricane Matthew had
crossed the western part of Haiti), covering both the 2010 and 2021 affected
zones; and (3) shaking intensity prediction maps.
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