POSTSEISMIC DEFORMATION FOLLOWING THE 2010 HAITI EARTHQUAKE: TIME-DEPENDENT SURFACE SUBSIDENCE INDUCED BY GROUNDWATER FLOW IN RESPONSE TO A SUDDEN UPLIFT

摘要

In this study we use Interferometric Synthetic Aperture Radar (InSAR) observations acquired by the TerraSARX (TSX) and the ALOS satellites to detect and characterize postseismic deformation induced by the 2010 Haiti earthquake. We obtained 8 TSX and 7 ALOS scenes covering the eastern portion of the earthquake rupture area, from before and after the earthquake. Interferometric data processing identified an elongated area of postseismic subsidence at the northeastern extent of the Leogane delta. The deformation is timedependent and occurred in the first 45 days after the earthquake. We suggest that the deformation occurred due to sediment compaction in the near-coast end of the delta in response to groundwater flow, as the groundwater table adjusted to new hydraulic conditions imposed by the sudden uplift of the delta by 60-80 cm with respect to unchanged sea level. These observations suggest a new mode of postseismic deformation: it occurs in the very shallow part of the crust (upper few meters) and is very different from the other three known postseismic deformation mechanisms (afterslip, viscoelastic relaxation and poroelastic response), which occur within deeper crustal levels (1-30 kilometers).