Tsunami Hazards, Modeling, and the Sedimentary Record

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Basic research to develop the geologic record of paleotsunamis and improve the ability to interpret that record is needed to mitigate tsunami risk in the U.S.

Image: Tsunami Recovery in American Samoa

Vasily Titov (left) of the NOAA Pacific Marine Environmental Laboratory and USGS oceanographer Bruce Jaffe (right) standing next to a tsunami warning sign. Signs like this warn people living on the coast to go to higher ground after an earthquake. Photo credit: Bruce Jaffe, USGS

Sediment Studies after Tsunamis

Survey Team visits Samoa and American Samoa October-November 2009

On September 29, 2009, an M 8.1 earthquake in the Samoa Islands region of the South Pacific Ocean caused a tsunami that resulted in 100's of lost lives. A rapid-response team of USGS scientists traveled to the Samoa Islands in October-November 2009 to collect time-sensitive data that would have been quickly degraded or destroyed by recovery activity and natural processes.

Rubble lies in a layer of sand covering the ground of a village, and a wrecked boat transported by tsunami lies on its side.

Photo taken about 100 meters inland at Kalmunai on Sri Lanka's east coast. Photo credit: Bruce Jaffe, USGS

The December 26, 2004 Indian Ocean Tsunami: Initial Findings on Tsunami Sand Deposits, Damage, and Inundation in Sri Lanka
Based on Survey Conducted January 9-15, 2005

From January 9-15, a multi-national team of scientists visited Sri Lanka to document the effects of the tsunami and provide government officials a summary of preliminary results of the surveys. This was the third group that documented the tsunami in Sri Lanka.

The 26 December 2004 Indian Ocean Tsunami: Initial Findings from Sumatra
Based on Survey Conducted January 20-29, 2005

An International Tsunami Survey Team (ITST) studying the effects of the December 26 tsunami on Indonesia's island of Sumatra documented wave heights of 20 to 30 m (65 to 100 ft) at the island's northwest end and found evidence suggesting that wave heights may have ranged from 15 to 30 m (50 to 100 ft) along at least a 100-km (60 mi) stretch of the northwest coast.

View from above looking at a beach area with damaged structures, and waves breaking far off in the distance.

View of tsunami damage from highway to Camaná, following the June 23, 2001 Peru Tsunami. Photo credit: Bruce Jaffe, USGS

Preliminary Analysis of Sedimentary Deposits from the June 23, 2001 Peru Tsunami

Shortly after the tsunami, a multi-national team of scientists visited Peru to document the effects of the tsunami. This group is referred to as the first International Tsunami Survey Team (1st ITST). In early September, a second group of scientists from the United States and Peru cooperated in a study of sediment deposited by the tsunami. The group included researchers from the United States Geological Survey USGS), la Dirección de Hidrografía y Navegación de la Marina de Guerra del Perú (DHN), Instituto Geofísico del Perú (IGP), Instituto Geologico, Minero y Metalurgico (INGEMMET), University of California, Santa Cruz (UCSC), University of Southern California (USC) and University of San Agustin (UNSA). This report contains photographs from the September trip, as well as some prelimary results and conclusions.

Photograph of the side of a hole dug into wet sediment that shows a boundary between sand brought in by a tsunami and the soil.

Figure 4: Typical tsunami deposit from a transect in Papua New Guinea. The tsunami deposited a gray-colored sand, here about 5 cm thick, on a brown soil containing roots. Photo credit: Bruce Jaffe, USGS

Preliminary Analysis of Sedimentary Deposits from the July 17, 1998 Papua New Guinea Tsunami

On July 17, 1998 a magnitude 7.6 earthquake was followed by a series of catastrophic tsunami waves that devastated several villages on the north coast of Papua New Guinea (PNG). Within a few weeks of the devastating tsunami, a multi-national team of scientists and engineers from Japan, the United States, Australia, and New Zealand entered the region installing seismographs, measuring water levels, and interviewing eyewitnesses.

Soon after the first team returned, a second group of international scientists became organized to retrieve the seismographs, collect more water-level and velocity data, assess damage to buildings and structures, and to examine the sediments left behind by the tsunami. The 2nd ITST arrived in Aitape, Papua New Guinea on September 29, 1998 and included representatives from Japan, the United States, Korea, and Papua New Guinea. This web page describes the efforts of the USGS scientists who participated in the 2nd ITST.

April 2011 in waterfront area of Tohoku, Japan following the March 11, 2011 earthquake and tsunami.

April 2011 in waterfront area of Tohoku, Japan following the March 11 2011 earthquake and tsunami. Photo credit: Rob Kayen, USGS

Our Research

The 11 March 2011 Tohoku-oki tsunami underscores that the U.S. is at risk from a deadly, devastating tsunami. The extent of risk is not known. However, the 2009 Samoa tsunami, geologic evidence in the Pacific Northwest and to a lesser degree the Caribbean, historical records in Hawaii, and Alaska, and modeling studies for California and the U.S. East Coast, all indicate that there is significant risk to the US from tsunamis. The effect of a tsunami at a coast, and the resulting risk, is the result of processes that control its generation, propagation, and inundation. Although potential tsunami sources (e.g., underwater earthquakes, landslides) can be identified, it is difficult, if not impossible, to predict with any certainty the largest possible tsunami that will impact an area based solely on current knowledge of source character and tsunami generating capacity. This is borne out by the 11 March 2011 tsunami that was larger in many regions in Japan than the largest historical or predicted tsunami. However, the geologic record did portend that a mega-tsunami would hit eastern Japan. The geologic record revealed that on average every 1000 years a mega-tsunami similar to the one on 11 March hits northeastern Japan.

Basic research to develop the geologic record of paleotsunamis and improve the ability to interpret that record is needed to mitigate tsunami risk in the U.S.

Objectives

The objectives of this project are to improve understanding of tsunamis, to develop techniques to assess the threat they pose, and to develop the paleotsunami record using sedimentary deposits. See tasks for specific research objectives.

What could be more relevant than research that can save lives? This project does exactly that by increasing the understanding of tsunami hazard in the U.S. This understanding informs mitigation of tsunami hazard in numerous ways including allowing development and refinement of evacuation plans, coastal zoning, and tsunami education.

Approach

Our strategy is to apply knowledge and skill gained from past USGS tsunami projects to paleotsunami deposit studies in locations with a known, but not well defined, tsunami hazard. Because the ability to identify and interpret paleotsunami deposits is still an emerging science, by necessity our approach includes targeted studies that develop methods for utilizing tsunami deposits in hazard assessment. These studies increase the value of the location-based paleotsunami studies. The locations of the paleotsunami studies are driven primarily by tsunami hazard potential, but also partially by opportunities to collaborate with researchers both inside and outside of the USGS. This collaboration leverages USGS resources and expertise. Paleotsunami studies will be phased, with initial investigations and more detailed, focused investigations in areas where paleotsunamis deposits are found to assess tsunami hazard. Detailed studies may include tsunami generation, propagation, and inundation modeling and source evaluation components.