Abstract
Abstract. The devastating Mw 7.1 Haiti earthquake in 2010 was accompanied by local tsunamis that caused fatalities and damage to coastal infrastructure. Some were triggered by slope failures of river deltas in the close vicinity of the epicenter, while others, 30 to 50 km to the north across the Bay of Gonâve, are well explained by the reverse component of coseismic ground motion that accompanied this mostly strike-slip event. However, observations of run-up heights up to 2 m along the southern coast of the island at distances up to 100 km from the epicenter, as well as tide gauge and DART buoy records at distances up to 600 km from the epicenter, have not yet received an explanation. Here we demonstrate that these observations require a secondary source, most likely a submarine landslide. We identify a landslide scar 30 km from the epicenter off the southern coast of Haiti at a depth of 3500 m, where ground acceleration would have been sufficient to trigger slope failure in soft sediments. This candidate source, 2 km3 in volume, matches observations remarkably well assuming that the sediment collapse obeys a viscous flow with an initial apparent viscosity of 2×105 Pa s. Although that particular source cannot be proven to have been activated in 2010, our results add to a line of evidence that earthquake-triggered submarine landslides can cause significant tsunamis in areas of strike-slip tectonic regime.
Highlights
The devastating Mw 7.1 Haiti earthquake in 2010 occurred within the Caribbean–North America plate boundary, where oblique relative motion at 19 mm yr−1 is partitioned between shortening on the North Hispaniola fault to the north and strike-slip motion on the E–W-striking Septentrional and Enriquillo faults throughout the island (Fig. 1; Symithe et al, 2015)
The fact that the earthquake source approximately matches observed arrival times at the tide gauge and DART buoy is an indication that a possible landslide source should be located fairly close to the epicentral area, which is a requirement for seafloor acceleration to be sufficient to trigger slope failure
We have shown that observations of run-up heights up to 2 m along the southern coast of the Haiti at distances up to 100 km from the epicenter, as well as tide gauge and DART buoy records at distances up to 600 km from the 12 January 2010 epicenter, require a secondary source and can be explained by a submarine landslide
Summary
The devastating Mw 7.1 Haiti earthquake in 2010 occurred within the Caribbean–North America plate boundary, where oblique relative motion at 19 mm yr−1 is partitioned between shortening on the North Hispaniola fault to the north and strike-slip motion on the E–W-striking Septentrional and Enriquillo faults throughout the island (Fig. 1; Symithe et al, 2015). A similar ad hoc procedure was proposed by Newman et al (2011) for the 2010 Mentawai, Indonesia, earthquake in order to account for the discrepancy between coseismic slip inverted from teleseismic waves and actual slip derived from geodetic measurements This artificially lowered rigidity can account for slow ruptures at subductions – “tsunami earthquakes” (Kanamori, 1972) – such as in Mentawai in 2010 or in Java in 2006 (Hébert et al, 2012), but the Haiti earthquake fault ruptured at 2.6 km s−1, a regular rupture velocity (de Lépinay et al, 2011). We show that this latter hypothesis is very likely, in line with the growing set of evidence linking tsunamis along strike-slip faults to submarine landslides (e.g., Ma et al, 1991; Yalçıner et al, 2002; Rodriguez et al, 2017)
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