Tsunami and earthquake in Chile Part 2

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1 EUROPEAN COMMISSION DIRECTORATE GENERAL JRC JOINT RESEARCH CENTRE Institute for the Protection and Security of the Citizen Global Security and Crisis Management Unit CriTech Sunday, 28 February 2010 Executive Summary On 2/27/2010 6:34:17 AM UTC an earthquake of magnitude 8.3 and depth 59.4km has struck an moderately populated area in the Bio-Bio Province (population: 1.7 million) in Chile. GDACS estimates the likelihood for need of international humanitarian intervention to be high (Red alert). Tsunami and earthquake in Chile Part 2 TS CHL, EQ CHL Part 1 of this report indicated the main locations expected to be reached by the Tsunami. In this section we can report the real measured height and the comparison with further calculations performed today. Fig. 1 Location of main event and its aftershocks Current Situation (at 27/2/ :45 CET) The Tsunami hit Peru coast mostly between latitudes -40 and -26. The most damage was in front of the fault, which is currently estimated 400 km long, centered on latitude , longitude , thus just 5 km from the coast. 87 fatalities are currently reported by media. The Tsunami should have had an initial deformation of 8.5m but as it was relatively deep (36 km), the surface water elevation should have been in the order of 2.5-3m. This is why on the coast in front of the fault (Talcahuano) the maximum measured height is 2.34 m. GAUGE LOCATION LAT LON TIME AMPL PER QUEPOS CR 0.0N 9.4E 1418Z 0.24M / 0.8FT 44MIN BALTRA GALAPAGS EC 0.4S 90.3W 1313Z 0.25M / 0.8FT 36MIN EASTER CL 27.2S 109.5W 1205Z 0.35M / 1.1FT 52MIN ANCUD CL 41.9S 73.8W 0838Z 0.62M / 2.0FT 84MIN CALLAO LA-PUNTA PE 12.1S 77.2W 1029Z 0.36M / 1.2FT 30MIN ARICA CL 18.5S 70.3W 1008Z 0.94M / 3.1FT 42MIN IQUIQUE CL 20.2S 70.1W 0907Z 0.28M / 0.9FT 68MIN ANTOFAGASTA CL 23.2S 70.4W 0941Z 0.49M / 1.6FT 52MIN DART LIMA S 86.4W 0941Z 0.24M / 0.8FT 36MIN CALDERA CL 27.1S 70.8W 0843Z 0.45M / 1.5FT 20MIN TALCAHUANO CL 36.7S 73.4W 0653Z 2.34M / 7.7FT 88MIN Joint Research Centre, I Ispra (VA), Italy 1

2 COQUIMBO CL 30.0S 71.3W 0852Z 1.32M / 4.3FT 30MIN CORRAL CL 39.9S 73.4W 0739Z 0.90M / 2.9FT 16MIN SAN FELIX CL 26.3S 80.1W 0815Z 0.53M / 1.7FT 08MIN VALPARAISO CL 33.0S 71.6W 0708Z 1.29M / 4.2FT 20MIN The Tsunami in the meantime is travelling in the Pacific Ocean. It is expected to reach New Zealand in about 13 h but the maximum expected height is certainly lower than 1m, maybe less (Fig. 1). We are performing at the moment a Pacific wide calculation based on the current conditions. On Easter Island, that has been partly evacuated as being on the trajectory of the Tsunami, the maximum measured height was 35 cm. Fig. 2 - NOAA calculation of travel time and wave height Post Event Calculations performed today On the basis of the preliminary information provided by USGS it is possible to perform the following calculation suing the JRC-SWAN model. * EPICENTER * Lat= * degree Lon= * degree Mag= 8.8 * Richter Scale Date= 27/02/2010 6:34 * * Fault parameters * lenght= 398 * km width= 111 * km strike= 16 * degree (geog North=0) slip= 8.5 * m dip= 14 * degree rake= 90 * degree depth= 35 * km Joint Research Centre, I Ispra (VA), Italy 2

3 With these parameters the agreement with the measured quantities is rather good. The comparison is performed by analysing the locations 1 to 3 in the figure below. For point 4 the measurement failed Fig. 3 JRC calculation of Chilean tsunami The level in front of the fault [1] decreases just after the earthquake and then rises about 22 minutes after the event of about 2.5 m. The behavior in Valparaiso [3] is quite different because the level shows a sudden increase after the event and then increases only later, at 27 min. At point [2], below the fault and probably out of the deformation location, the level increases much later, 1h, without an initial increase. Other calculations are ongoing using the HYFLUX2 code in order to estimate the inundation on land close to the epicentre. The results of these calculations should be available in the next hours. Joint Research Centre, I Ispra (VA), Italy 3

4 Comparison of measured with calculated Chile Talcahuano, /-73.1 omparison of measured and calculated values in Valparaiso, / C Comparison of measured and calculated level in Corral, / Fig. 4 Comparison of measured and calculated parameters Joint Research Centre, I Ispra (VA), Italy 4

5 ANNEX 1 Tectonic setting and preliminary seismic parameters This earthquake occurred at the boundary between the Nazca and South American tectonic plates. The two plates are converging at a rate of 8.0 cm per year. The earthquake occurred as thrust-faulting on the interface between the two plates, with the Nazca plate moving down and landward below the South American plate (Fig. 1). Historic events This area is one of the most active regions in the world generating strong earthquakes. Since 1973, there have been 13 events of magnitude 7.0 or greater. The February 27 shock originated about 230 km north of the source region of the magnitude 9.5 earthquake of May, 1960 Figure A1. Peru-Chile subduction zone map. ( ile/background/geology/geology.html) the largest instrumentally recorded earthquake in the world. This magnitude 9.5 earthquake killed 1655 people in southern Chile and unleashed a tsunami that crossed the Pacific, killing 61 people in Hawaii, Japan, and the Philippines. Approximately 870 km to the north of the February 27 earthquake is the source region of the magnitude 8.5 earthquake of November, This great quake significantly impacted central Chile, killing several hundred people and causing severe property damage. The 1922 quake generated a 9- meter local tsunami that inundated the Chile coast near the town of Coquimbo; the tsunami also crossed the Pacific, washing away boats in Hilo harbor, Hawaii. The magnitude 8.8 earthquake of February 27, 2010 ruptured the portion of the South American subduction zone separating these two massive historical earthquakes. The table below reports the events greater than Mw6.0 that occurred between are shown. In addition another earthquake of 6.0 occurred 19 Decemeber 2008 in 2008 (see figure of historic moment tensor). Joint Research Centre, I Ispra (VA), Italy 5

6 Characteristic of events in Chile greater than Mw 6.0. From (NGDC). Joint Research Centre, I Ispra (VA), Italy 6