Summary

Kingston, Jamaica has a long history of natural disasters, including large earthquakes, landslides, and tsunamis The city is situated near the Enriquillo-Plantain Garden Fault Zone, which has made recent news as the fault responsible for the 12 January 2010 Haiti earthquake. Submarine slides and near-shore liquefaction may have triggered several tsunamis in Kingston Harbor. Here, we present preliminary results assessing the frequency, location, and pattern of sliding and liquefaction in the harbor. Ultimately, we will use these data to constrain the frequency of earthquake events, and to assess geological hazards across the region.

Introduction

The great Jamaican earthquakes of 1692 and 1907 both triggered severe ground liquefaction and massive landslides in and around Kingston Harbor (Tabor, 1920). Local tsunamis were generated near or within Kingston Harbor during these earthquakes. Submarine mass movements represent the most likely tsunami trigger source. We examine seafloor morphology and subsurface sedimentary structures, in addition to long-term patterns of erosion and deposition. We use these data to reconstruct submarine slide magnitude, sediment accumulation rate, the frequency of slides, and associated tsunami hazard these slides may pose. We will ultimately use these data to assess which areas around Kingston are at high risk for liquefaction, slope failure, and tsunamis.

Methods

We collected many 2D high-resolution CHIRP lines using a Knudson 320B Echosounder to constrain the location, size, and frequency of submarine slope failure in Kingston Harbor. Detailed nautical charts from 1747 to the present were digitized and gridded in ArcGIS We calculated change in seafloor depth over time, yielding spatial estimates of erosion and deposition for the past several hundred years.

Preliminary Conclusions

The town of Port Royal, situated on the southeastern end of the Harbor, sank vertically between 2 and 10m during the 1692 event, but no clear submarine slide deposit is seen in subsurface reflectors. This may be attributed to 1) the disruption of continuous reflectors due to liquefaction, 2) poor penetration of acoustic waves into the shallow sediments in the area of historic Port Royal, perhaps due to higher sand and gravel content, or 3) removal of sediment by underwater currents. Nonetheless, at least one well imaged slide exists in the northeast corner of the harbor. The slide’s position at the top of the sediment column indicates a recent origin. It is adjacent to the known tsunami location of the 1907 event. Preliminary analysis of other data in this area suggest multiple slide events may have occurred in this region. In addition, analysis of both old and new bathymetric images reveals significant (tens of meters) of sediment accumulation alone the southern half of the Palisadoes sand spit, and this region may be particularly prone to liquefaction. Preliminary slide-centered tsunami models are consistent with accounts of the 1907 event, but not the 1692 event. Future work will focus on refining the timing, size, and tsunami potential from liquefaction and sliding in the harbor. Core samples will be retrieved from submarine slide deposits for carbon dating and geotechnical analysis.

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