Preliminary Analysis of Sedimentary Deposits from the June 23, 2001 Peru Tsunami
A Cooperative Study by the USGS, la Dirección de Hidrografía y Navegación de la Marina de Guerra del Perú, Instituto Geofísico del Perú, Instituto Geologico, Minero y Metalurgico, University of California, Santa Cruz, University of Southern California, and University of San Agustin.
September 4 - September 18, 2001
On June 23, 2001 a deadly tsunami hit the southern coast of Peru, triggered by a massive earthquake of moment magnitude 8.4, the largest earthquake recorded worldwide in 35 years. The tsunami was observed in many coastal areas of the Pacific including Peru, Chilé, Hawaii, and Japan. Hardest hit was the region around Camaná, Peru, where more than 20 people died as a result of the tsunami and thousands of homes, hotels, and restaurants were destroyed. 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.
Preliminary modeling of the tsunami was done by Eric Geist of the USGS. The modeling results predict that the largest run-ups are centered around Camaná, even though the epicenter for the earthquake was approximately 100 km to the NW. This was because the largest slip values, which are directly linked to the initial tsunami amplitude, were centered beneath Camaná. Model results, including a tsunami animation, are available.
Visit the U.S. National Oceanic and Atmospheric Administration Pacific Marine Environmental Laboratory (NOAA/PMEL) for information on the Peru tsunami event of June 23, 2001. Previous tsunami sediment surveys include a survey of sediments deposited by the 1998 Papua/New Guinea Tsunami.
Participants in the Peru Tsunami Sediment Survey
USGS: Bruce Jaffe, Guy Gelfenbaum, Roberto Anima, David Rubin
UCSC: Robert Peters
USC: Matt Swensson
DHN: Daniel Olcese, Luis Bernales Anticona
IGP: Juan Carlos Gomez, Leonidas Ocala, Porfirio Huaco, Oswaldo Velasqez Cahuas, Hector Alamain
INGEMMET: Antonio Guzman Martinez, German Valenzuela
USA: Percy Colque Riega
The Importance of Studying Tsunami Sediments
Tsunamis often leave a layer of sediments that may be preserved in the geologic record. The geologic record may then be used to help assess tsunami hazard. In some cases, this record may be the only evidence that a region may be at risk from a tsunami. Where more than one tsunami deposit is preserved in a stratigraphic sequence, the record may help determine how often a tsunami is likely to occur. Tsunami sediments may also record important information about the wave that deposited them. By examining the thickness and grain size distribution of tsunami deposits, scientists may be able to deduce the wave height and flow velocity of the wave. Wave height and flow velocity are among the most important properties of a tsunami that determine how destructive the wave is. By studying sediments from recent tsunamis, we may be better able identify and interpret tsunami sediments in the geologic record.
Survey and Methods
USGS and Peruvian scientists measured tsunami sediment thickness, run-up, inundation distance, and topographic profiles for six shore-normal transects along 50 km of coastline in the vicinity of Camaná, Peru. More than 120 samples were collected for laboratory analyses for grain size distribution, microfossils, mineralogy, and chemistry. Sedimentary characteristics of the tsunami deposits and underlying material were logged and photo-documented. Box cores and sediment peels were taken at several sites to preserve the stratigraphy of the sediments. Erosion, flow-direction indicators, water marks on buildings, and damage to structures were also documented. Local residents were interviewed for their observations of the tsunami and local conditions before and after the tsunami. In addition to participating in the field survey, our Peruvian colleagues provided maps, supplied photographs taken before and shortly after the tsunami, and were invaluable for their knowledge of the area.
Damage to Structures
Tsunami Runup
Sedimentary Deposits
Sedimentary deposits from the tsunami were found in most places where significant inundation occurred. Where the deposits were overlying a known preexisting surface that was texturally distinct, such as farm soils (La Quinta, Playa Jahuay), identification was fairly simple. Where the underlying material was beach sand that was similar both texturally and visually, identification was more difficult. Identification of tsunami deposits was based on several criteria, including differences in grain-size and color. In tsunami deposits, grain size generally fines upwards and rip-up clasts (pieces of material from the underlying sediment entrained by the tsunami) may be present. The base of the deposit erodes underlying structures and a heavy mineral layer may be present at the base. Underlying sands were often trampled while tsunami sands were relatively undisturbed. Many of the deposits had multiple layers. Many of the elements found in tsunami deposits from Papua New Guinea, such as rip-up clasts, multiple layers, and fining upwards sequences, were also found in Peru.
Results
- Sediment deposits were found at all sites.
- Sediment deposit thickness is variable, effected by distance from the shoreline, local topography, and change in slope.
- Only a few sites had easily identifiable deposits.
- Some deposits were normally graded, some were inversely graded, and some had no visible grading.
- Flow indicators suggest significant onshore flow and weaker, but significant offshore flow.
The deposits from the tsunami exhibited a wide variety of forms throughout the study area. Thickness varied both with distance inland and with site. The thickest deposits measured were at Amecosupe. While sedimentary structures were usually absent, many deposits contained 2-4 internal layers. Each layer is believed to represent deposition from a single wave within the tsunami wave train. Eye-witness accounts report that the tsunami consisted of 3-4 waves, with the second and third waves being the largest. The greatest run-up measured (from mid-swash, uncorrected for tides) was 8.2 meters at Playa la Chira. The greatest inundation distance measured (from mid-swash, uncorrected for tides) was 760 meters at La Quinta. The 1st ITST measured inundation distances of up to 1 km at some locations.
Acknowledgments
Funding for the participation of the USGS in the 2001 Peru Tsunami Sediment Survey came from the USGS Coastal and Marine Geology Program, Dr. John Haines, Program Coordinator. We would like to thank Admiral Hector Soldi Soldi, Director de Hidrografia y Navagacion, Peruvian Navy, for inviting the USGS to participate in this survey, for DHN's assistance with logistics, and for the support of DHN scientists who participated in this survey. We thank Rómulo Mucho, Chairman of the Board of Directors of the INGEMMET, and Dr. Ronald Woodward, President IGP for the support of the IGP and INGEMMET scientists who participated in the survey. We thank Miguel Ypez, Foreign Service National, US Embassy, Lima for his help and Jean Weaver, USGS/GD International Programs Latin America leader for assisting in arranging for participation of the USGS personnel. We send our condolences for those lost in the tsunami. We thank the people of Camaná for their warm welcome and support, and wish them a rapid recovery in these difficult times.
Below are other science projects associated with this project.
Tsunami and Earthquake Research
Preliminary Analysis of the Tsunami Generated by the June 23, 2001 Peru Earthquake
A Cooperative Study by the USGS, la Dirección de Hidrografía y Navegación de la Marina de Guerra del Perú, Instituto Geofísico del Perú, Instituto Geologico, Minero y Metalurgico, University of California, Santa Cruz, University of Southern California, and University of San Agustin.
September 4 - September 18, 2001
On June 23, 2001 a deadly tsunami hit the southern coast of Peru, triggered by a massive earthquake of moment magnitude 8.4, the largest earthquake recorded worldwide in 35 years. The tsunami was observed in many coastal areas of the Pacific including Peru, Chilé, Hawaii, and Japan. Hardest hit was the region around Camaná, Peru, where more than 20 people died as a result of the tsunami and thousands of homes, hotels, and restaurants were destroyed. 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.
Preliminary modeling of the tsunami was done by Eric Geist of the USGS. The modeling results predict that the largest run-ups are centered around Camaná, even though the epicenter for the earthquake was approximately 100 km to the NW. This was because the largest slip values, which are directly linked to the initial tsunami amplitude, were centered beneath Camaná. Model results, including a tsunami animation, are available.
Visit the U.S. National Oceanic and Atmospheric Administration Pacific Marine Environmental Laboratory (NOAA/PMEL) for information on the Peru tsunami event of June 23, 2001. Previous tsunami sediment surveys include a survey of sediments deposited by the 1998 Papua/New Guinea Tsunami.
Participants in the Peru Tsunami Sediment Survey
USGS: Bruce Jaffe, Guy Gelfenbaum, Roberto Anima, David Rubin
UCSC: Robert Peters
USC: Matt Swensson
DHN: Daniel Olcese, Luis Bernales Anticona
IGP: Juan Carlos Gomez, Leonidas Ocala, Porfirio Huaco, Oswaldo Velasqez Cahuas, Hector Alamain
INGEMMET: Antonio Guzman Martinez, German Valenzuela
USA: Percy Colque Riega
The Importance of Studying Tsunami Sediments
Tsunamis often leave a layer of sediments that may be preserved in the geologic record. The geologic record may then be used to help assess tsunami hazard. In some cases, this record may be the only evidence that a region may be at risk from a tsunami. Where more than one tsunami deposit is preserved in a stratigraphic sequence, the record may help determine how often a tsunami is likely to occur. Tsunami sediments may also record important information about the wave that deposited them. By examining the thickness and grain size distribution of tsunami deposits, scientists may be able to deduce the wave height and flow velocity of the wave. Wave height and flow velocity are among the most important properties of a tsunami that determine how destructive the wave is. By studying sediments from recent tsunamis, we may be better able identify and interpret tsunami sediments in the geologic record.
Survey and Methods
USGS and Peruvian scientists measured tsunami sediment thickness, run-up, inundation distance, and topographic profiles for six shore-normal transects along 50 km of coastline in the vicinity of Camaná, Peru. More than 120 samples were collected for laboratory analyses for grain size distribution, microfossils, mineralogy, and chemistry. Sedimentary characteristics of the tsunami deposits and underlying material were logged and photo-documented. Box cores and sediment peels were taken at several sites to preserve the stratigraphy of the sediments. Erosion, flow-direction indicators, water marks on buildings, and damage to structures were also documented. Local residents were interviewed for their observations of the tsunami and local conditions before and after the tsunami. In addition to participating in the field survey, our Peruvian colleagues provided maps, supplied photographs taken before and shortly after the tsunami, and were invaluable for their knowledge of the area.
Damage to Structures
Tsunami Runup
Sedimentary Deposits
Sedimentary deposits from the tsunami were found in most places where significant inundation occurred. Where the deposits were overlying a known preexisting surface that was texturally distinct, such as farm soils (La Quinta, Playa Jahuay), identification was fairly simple. Where the underlying material was beach sand that was similar both texturally and visually, identification was more difficult. Identification of tsunami deposits was based on several criteria, including differences in grain-size and color. In tsunami deposits, grain size generally fines upwards and rip-up clasts (pieces of material from the underlying sediment entrained by the tsunami) may be present. The base of the deposit erodes underlying structures and a heavy mineral layer may be present at the base. Underlying sands were often trampled while tsunami sands were relatively undisturbed. Many of the deposits had multiple layers. Many of the elements found in tsunami deposits from Papua New Guinea, such as rip-up clasts, multiple layers, and fining upwards sequences, were also found in Peru.
Results
- Sediment deposits were found at all sites.
- Sediment deposit thickness is variable, effected by distance from the shoreline, local topography, and change in slope.
- Only a few sites had easily identifiable deposits.
- Some deposits were normally graded, some were inversely graded, and some had no visible grading.
- Flow indicators suggest significant onshore flow and weaker, but significant offshore flow.
The deposits from the tsunami exhibited a wide variety of forms throughout the study area. Thickness varied both with distance inland and with site. The thickest deposits measured were at Amecosupe. While sedimentary structures were usually absent, many deposits contained 2-4 internal layers. Each layer is believed to represent deposition from a single wave within the tsunami wave train. Eye-witness accounts report that the tsunami consisted of 3-4 waves, with the second and third waves being the largest. The greatest run-up measured (from mid-swash, uncorrected for tides) was 8.2 meters at Playa la Chira. The greatest inundation distance measured (from mid-swash, uncorrected for tides) was 760 meters at La Quinta. The 1st ITST measured inundation distances of up to 1 km at some locations.
Acknowledgments
Funding for the participation of the USGS in the 2001 Peru Tsunami Sediment Survey came from the USGS Coastal and Marine Geology Program, Dr. John Haines, Program Coordinator. We would like to thank Admiral Hector Soldi Soldi, Director de Hidrografia y Navagacion, Peruvian Navy, for inviting the USGS to participate in this survey, for DHN's assistance with logistics, and for the support of DHN scientists who participated in this survey. We thank Rómulo Mucho, Chairman of the Board of Directors of the INGEMMET, and Dr. Ronald Woodward, President IGP for the support of the IGP and INGEMMET scientists who participated in the survey. We thank Miguel Ypez, Foreign Service National, US Embassy, Lima for his help and Jean Weaver, USGS/GD International Programs Latin America leader for assisting in arranging for participation of the USGS personnel. We send our condolences for those lost in the tsunami. We thank the people of Camaná for their warm welcome and support, and wish them a rapid recovery in these difficult times.
Below are other science projects associated with this project.