Field Survey of the 27 February 2010 Chile Tsunami
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Pure Appl. Geophys. 168 (2011), 1989–2010 Ó 2011 Springer Basel AG DOI 10.1007/s00024-011-0283-5 Pure and Applied Geophysics Field Survey of the 27 February 2010 Chile Tsunami 1 2 3 4 5 HERMANN M. FRITZ, CATHERINE M. PETROFF, PATRICIO A. CATALA´ N, RODRIGO CIENFUEGOS, PATRICIO WINCKLER, 6 7 8 8 8 NIKOS KALLIGERIS, ROBERT WEISS, SERGIO E. BARRIENTOS, GIANINA MENESES, CAROLINA VALDERAS-BERMEJO, 9 6 10 4 4 CARL EBELING, ATHANASSIOS PAPADOPOULOS, MANUEL CONTRERAS, RAFAEL ALMAR, JUAN CARLOS DOMINGUEZ, 11,12 and COSTAS E. SYNOLAKIS Abstract—On 27 February 2010, a magnitude Mw = 8.8 Islands of Santa Marı´a, Mocha, Juan Ferna´ndez Archipelago, and earthquake occurred off the coast of Chile’s Maule region causing Rapa Nui (Easter). The collected survey data include more than substantial damage and loss of life. Ancestral tsunami knowledge 400 tsunami flow depth, runup and coastal uplift measurements. from the 1960 event combined with education and evacuation The tsunami peaked with a localized runup of 29 m on a coastal exercises prompted most coastal residents to spontaneously evac- bluff at Constitucio´n. The observed runup distributions exhibit uate after the earthquake. Many of the tsunami victims were significant variations on local and regional scales. Observations tourists in coastal campgrounds. The international tsunami survey from the 2010 and 1960 Chile tsunamis are compared. team (ITST) was deployed within days of the event and surveyed 800 km of coastline from Quintero to Mehuı´n and the Pacific Key words: Tsunami, wave runup, coastal uplift, Chile, South Pacific Ocean. 1 School of Civil and Environmental Engineering, Georgia Institute of Technology, Savannah, GA 31407, USA. E-mail: 1. Introduction [email protected] 2 LP4 Associates LLC, Mercer island, WA, USA. E-mail: On 27 February 2010 at 06:34:14 UTC (local time [email protected] 3 Departamento de Obras Civiles, Universidad Te´cnica 03:34:14 am), a magnitude Mw = 8.8 earthquake Federico Santa Marı´a, Valparaı´so, Chile. E-mail: patricio.catalan@ occurred off the coast of Chile’s Maule region about usm.cl 100 km north of Concepcio´n(LAY et al., 2010;DELOUIS 4 Departamento de Ingenierı´a Hidra´ulica y Ambiental et al., 2010). The earthquake and tsunami caused sub- Escuela de Ingenierı´a, Pontificia Universidad Cato´lica de Chile, Santiago, Chile. E-mail: [email protected]; [email protected]; stantial damage and loss of life along Chile’s [email protected] continental coast, in the Juan Ferna´ndez Archipelago, 5 School of Ocean Engineering, Universidad de Valparaı´so, and on Easter Island (Rapa Nui). The number of tsu- Valparaı´so, Chile. E-mail: [email protected] 6 Department of Environmental Engineering, Technical nami victims among the total death toll was University of Crete, 73100 Chania, Greece. E-mail: nkalligeris@ significantly overestimated in initial reports and later isc.tuc.gr; [email protected] reduced to a ratio of one tsunami victim to every four 7 Department of Geology and Geophysics, Texas A&M University, College Station, TX, USA. E-mail: [email protected] deaths. The majority of the 521 fatalities are attributed 8 Departamento de Geofı´sica, Universidad de Chile, Santiago, to the earthquake, while the tsunami accounts for 124 Chile. E-mail: [email protected]; gianinameneses.p@gmail. victims concentrated in the coastal regions of Maule com; [email protected] (69) and Biobı´o (33), Juan Ferna´ndez Archipelago’s 9 Department of Earth and Planetary Sciences, Northwestern University, Evanston, IL, USA. E-mail: [email protected]. Robinson Crusoe Island (18), and Mocha Island (4). edu The 2010 Chile tsunami represents South America’s 10 Departamento de Ingenierı´a Informa´tica, Facultad de deadliest tsunami since the 1979 great Tumaco earth- Ingenierı´a, Universidad de Playa Ancha, Valparaı´so, Chile. E-mail: [email protected] quake and tsunami off Colombia’s Pacific coast, which 11 Department of Civil and Environmental Engineering, washed away more than 220 coastal residents in San University of Southern California, Los Angeles, CA 90089, USA. Juan, Narin˜o alone (HERD et al., 1981). E-mail: [email protected] 12 Hellenic Center for Marine Research, 19013 Anavyssos, During the 2010 Chile tsunami, the Pacific Tsu- Greece. nami Warning Center (PTWC) responded and issued 1990 H. M. Fritz et al. Pure Appl. Geophys. warnings 5 min after the earthquake, but because the from Quintero to Mehuı´n, including Santa Marı´a tsunami arrived within 30 min at many locations, Island in the Gulf of Arauco, Easter Island and official evacuations and warnings by local authorities Robinson Crusoe Island in the Juan Ferna´ndez were often not in place prior to the arrival of the Archipelago. A follow-up survey from 21 to 23 May tsunami. Fortunately, most coastal residents in Chile 2010 focused on Mocha Island. Aerial reconnaissance were aware of the tsunami risk and evacuated to high flights were conducted between Pelluhue and the ground as a result of ancestral tsunami knowledge, Arauco peninsula as well as over Robinson Crusoe regular evacuation drills and education programs and Mocha Islands. The survey teams documented (MARI´N et al., 2010). Most of the tsunami victims tsunami runup, flow depth and inundation; wave were Chilean tourists enjoying a late summer week- induced deposition or erosion, structural damage and end and staying overnight in low-lying coastal interviewed eyewitnesses using established protocols campgrounds. (SYNOLAKIS and OKAL, 2005). The Chile survey data The 27 February 2010 Maule earthquake was at recorded 419 tsunami runup and flow depth mea- the time the fifth largest event instrumentally recorded surements shown in Fig. 1 and Appendix Table 1.At and filled the longest standing seismic gap in Chile. most locations, the tsunami arrived as sea levels The epicenter was located in the center of the Con- passed through low tide (Fig. 2). Measured data were cepcio´n–Constitucio´n area [35–37°S] in south-central corrected for tide level at the time of tsunami arrival Chile, identified as a mature seismic gap by RUEGG on the basis of tide predictions provided by the et al. (2009). Pre-event estimates of a potential United Kingdom Hydrographic Office (pers. comm.: earthquake of 8.0 \ Mw \ 8.5 based on the accumu- Christopher Jones, Head of Tides, UKHO). A sig- lated slip deficit over the past 175 years were nificant variation in tsunami impact was observed conservative. The last large subduction zone earth- along Chile’s mainland at both local and regional quake in this south-central Chile region occurred on scales (Fig. 3). 20 February 1835 (DARWIN, 1851) and was of a similar The tsunami impact peaked with a localized estimated magnitude, close to Mw & 8.5 (LOMNITZ, maximum runup of 29 m at Constitucio´n along a 1970;BECK et al., 1998). The rupture zone of the 2010 steep coastal bluff (Fig. 3a). To the north of Con- event was situated immediately to the north of the stitucio´n the runup distribution exhibited a decaying rupture zone associated with the great 1960 earth- trend with runup heights typically between 5 and quake with Mw = 9.5 (PLAFKER and SAVAGE, 1970; 10 m exceeded only by a high point of 14 m runup on KANAMORI, 1977;CIFUENTES, 1989) and south of the a coastal bluff within 70 m of the shoreline at Caleta rupture zones corresponding to the 1928 Talca de Mostazal (Fig. 3c), 35 km south of San Antonio. earthquake (BECK et al., 1998) and the 1906 and 1985 Further to the north, runup remained uniformly below Valparaiso earthquakes (BARRIENTOS, 1995). Part of 5 m with typical heights of 3 m in the greater Val- the region was affected by the 1939 Chilla´n earth- paraı´so area. Nevertheless, at Llolleo, a campground quake Mw = 7.9, which was a slab-pull event with on low-lying ground along a lagoon adjacent to the release of tensional stresses within the down-going south of Chile’s main container terminal at San slab (CAMPOS and KAUSEL, 1990;BECK et al., 1998). Antonio was washed away during the tsunami. Low- Further north, the Talca earthquake of 1 December lying coastal dunes stabilized by vegetation offered 1928, was interpreted as a shallow dipping thrust partial protection to some coastal communities such event (LOMNITZ, 1970;BECK et al., 1998). as Punta de Lobos. Variable runup heights within a 5–15 m range were observed between Constitucio´n and Punta Morguilla some 300 km to the south. In a 2. Post-Tsunami Reconnaissance few significant cases, however, runup heights decreased below 5 m along this stretch of coastline. The surveys took place using three integrated These included the epicentral area at Cobquecura as survey groups from 7 to 24 March 2010 covering an well as the east coasts inside the Bay of Concepcio´n 800 km stretch of south-central Chilean coastline and the Gulf of Arauco. Further to the south between Vol. 168, (2011) Field Survey of the 27 February 2010 Chile Tsunami 1991 Tsunami Height [m] 30 25 20 15 10 5 0 2010 EQ Valparaíso Robinson 1960 EQ 33 Crusoe Island San Antonio Santiago o elag Archip Juan Fernández Navidad 34 Pichilemu Iloca 35 Constitución n Pelluhue S) a Curanipe o e CHILE 36 c Cobquecura O Dichato Kilometers 050100 150 c i Santa Concepción/ f i Maria Talcahuano 0 25 50 75 c Miles Latitude ( a 37 P Arauco h Lebu t u o Punta Morguilla S 38 Tirúa Mocha Puerto Saavedra 39 Mehuín Flow Depth Runup 40 80 79 78 77 76 75 74 73 72 71 70 69 Figure 1 Tsunami flow depths and runup heights measured along 800 km of Chilean coastline from Quintero to Mehuı´n including the Islands of Santa Marı´a, Mocha, and Robinson Crusoe (Juan Ferna´ndez Archipelago) Punta Morguilla and Mehuı´n the runup remained observed and recorded on cell phone videos by eye- mostly below 5 m with exception of the greater Tiru´a witnesses on the south shores of the U-shaped and area.