APPLICATIONS OF LIDAR IN THE SCIENTIFIC RESPONSE TO MAJOR EARTHQUAKES: LESSONS FROM HAITI AND MEXICO

The infrastructure now exists to rapidly collect and analyze massive terrain data sets in concert with traditional earthquake geology field response. Examples from recent earthquakes in Haiti and Baja California show the potential for new discoveries to be made with rapid post-event laser scanning. Within days of the 12 January M_W7.0 Haiti earthquake, over 850 sq. km of airborne lidar data were collected, including 60 km of the causative Enriquillo fault zone. Though no surface rupture from the 2010 event was detected, analysis of the lidar quickly revealed abundant evidence for prior, and likely larger surface-rupturing earthquakes. The smallest surface displacements of 6 to 8 meters that we could remotely resolve with the lidar data probably represent slip that accrued over multiple events. We both identified additional displaced landforms and increased measurement precision by evaluating the raw point-cloud data in concert with automatically generated bare-earth models. Offsets smaller than 6 meters may be resolvable from the lidar point clouds, but are most likely obscured by dense vegetation. Rapid post-event terrestrial laser-scanning of scarps formed by fault slip during the 4 April M_W7.2 El Mayor-Cucapah earthquake illuminate the fine structure of fault free-faces and reveals striae indicating differing slip directions in 2010 versus the penultimate event. These data also capture abundant near-fault warping and distributed deformation that will be quickly obscured by erosion. Airborne surveys of this earthquake rupture could not be acquired in time to be analyzed in concert with the field observation campaign. However, these data will form an important compliment to the field data by allowing independent evaluation of field-based displacement measurements and archiving the rupture for additional analysis. Ideally, following future major surface-rupturing earthquakes, airborne and terrestrial lidar data will be collected together immediately to capture the rupture in a pristine state, enable remote mapping, and guide fieldwork. Ultimately, precisely quantifying earthquake surface displacements should incorporate the full set of information available in lidar point clouds, and be closely coupled in real-time with field observations.