Coastal Impacts of the March 11th Tohoku, Japan Tsunami in the Galapagos Islands
On March 11, 2011 at 5:46:23 UTC (March 10 11:46:23 PM Galapagos Local Time), the Mw 9.0 Great East Japan Earthquake occurred near the Tohoku region off the east coast of Japan, spawning a Pacific-wide tsunami. Approximately 12,000 km away, the Galapagos Islands experienced moderate tsunami impacts, including flooding, structural damage, and strong currents. In this paper, we present observations and measurements of the tsunami effects in the Galapagos, focusing on the four largest islands in the archipelago; (from west to east) Isabela, Santiagio, Santa Cruz, and San Cristobal. Access to the tsunami affected areas was one of the largest challenges of the field survey. Aside from approximately ten sandy beaches open to tourists, all other shoreline locations are restricted to anyone without a research permit; open cooperation with the Galapagos National Park provided the survey team complete access to the Islands coastlines. Survey locations were guided by numerical simulations of the tsunami performed prior to the field work. This numerical guidance accurately predicted the regions of highest impact, as well as regions of relatively low impact. Tide-corrected maximum tsunami heights were generally in the range of 3–4 m with the highest runup of 6 m measured in a small pocket beach on Isla Isabela. Puerto Ayora, on Santa Cruz Island, the largest harbor in the Galapagos experienced significant flooding and damage to structures located at the shoreline. A current meter moored inside the harbor recorded relatively weak tsunami currents of less than 0.3 m/s (0.6 knot) during the event. Comparisons with detailed numerical simulations suggest that these low current speed observations are most likely the result of data averaging at 20-min intervals and that maximum instantaneous current speeds were considerably larger. Currents in the Canal de Itabaca, a natural waterway between Santa Cruz Island and a smaller island offshore, were strong enough to displace multiple 5.5-ton navigation buoys. Numerical simulations indicate that currents in the Canal de Itabaca exceeded 4 m/s (~8 knots), a very large flow speed for a navigational waterway.
- Abe, K. (1979). Size of great earthquakes of 1837–1979 inferred from tsunami data, J. Geophys. Res. 84, 1561–1568.Google Scholar
- Arcos, M., MacInnes, B., Arreaga, P., Rivera-Hernandez, F., Weiss, R., and Lynett, P., “A Meter-Thick Sedimentary Package Caused By the 2011 Tohoku Tsunami in El Garrapatero, Galapagos—A Record of Sedimentary Deposition Enabled by Tsunami Erosion,” in review for Quaternary Research, 2012.Google Scholar
- Bailey, K., 1976. Potassium-Argon Ages from the Galápagos Islands. Science 192, 465–467.Google Scholar
- Borrero, J., Rob Bell, Claudia Csato, Willem Delange, Derek Goring, S. Dougal Greer, Vernon Pickett, and William Power Observations, Effects and Real Time Assessment of the March 11, 2011 Tohoku-oki Tsunami in New Zealand, Pure Appl. Geophys. doi:10.1007/s00024-012-0492-6.
- Dominey-Howes, D., Dengler, L., Dunbar, P., Kong, L., Fritz, H., Imamura, F., McAdoo, B., Satake, K.,Yalciner, A., Yamamoto, M., Yulianto, E., Koshimura, S., and Borrero, J. (2012). International Tsunami Survey Team (ITST) Post-Tsunami Survey Field Guide. 2nd Edition. UNESCO-IOC, Paris.Google Scholar
- Kanamori, H., and K. McNally Variable rupture mode of the subduction zone along the Ecuador–Colombia coast, Bull. Seismol. Soc. Am., 72,. 1241–1253, 1982.Google Scholar
- Kanoglu, U. and Synolakis, C.E., 1998, Long wave runup on piecewise linear topographies, Journal of Fluid Mechanics, 374, 1-28.Google Scholar
- Kim, D.-H. and Lynett, P. (2011) “Turbulent Mixing and Scalar Transport in Shallow and Wavy Flows.” Physics of Fluids, v. 23 (1), doi:10.1063/1.3531716 (16 pages).
- Liu, P. L.-F., Y-S. Cho, M.J. Briggs, C.E. Synolakis, and U. Kanoglu Run-up of solitary waves on a circular island. J. Fluid Mech, 302:259–285, 1995.Google Scholar
- Lynett, P. (2007). “The Effect of a Shallow Water Obstruction on Long Wave Runup and Overland Flow Velocity.” Journal of Waterway, Port, Coastal, and Ocean Engineering (ASCE), v. 133(6), p. 455-462.Google Scholar
- Lynett, P., Borrero, J, Weiss, R., Son, S., Greer, D., and Renteria, W. “Observations and Modeling of Tsunami-Induced Currents in Ports and Harbors,” Earth and Planetary Science Letters, v. 327/328, pp. 68-74, doi:10.1016/j.epsl.2012.02.002, 2012.
- Mori, N., Takahashi, T., Yasuda, T. and Yanagisawa, H., (2011) Survey of the 2011 Tohku earthquake tsunami inundation and run-up. Geophys. Res. Lett. doi:10.1029/2011GL049210.
- Shiki, T., Tsuji, Y., Minoura, K., and Yamazaki, T. (eds) Tsunamiites – Features and Implication, 1st edition, (Elsevier Science, 2008).Google Scholar
- Son, S., Lynett, P., and Kim, D.-H. (2011) “Nested and Multi-Physics Modeling of Tsunami Evolution from Generation to Inundation.” Ocean Modelling, v. 38 (1-2), p. 96-113, doi: 10.1016/j.ocemod.2011.02.007.
- Synolakis, C. E. & Okal, E. A. 2005 1992–2002: perspective on a decade of post tsunami surveys. Adv. Nat. Technol. Hazards 23, 1–30.Google Scholar
- USGS, 2011. Finite Fault Model, Updated Result of the Mar 11, 2011 Mw 9.0 Earthquake Offshore Honshu, Japan. http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usc0001xgp/finite_fault.php.
- Werner, R., Hoernle, K., Barckhausen, U., Hauff, F., 2003. Geodynamic evolution of the Galápagos hot spot system (Central East Pacific) over the past 20 m.y.: Constraints from morphology, geochemistry, and magnetic anomalies. Geochem. Geophys. Geosyst. 4, 28 PP.Google Scholar
- Wessel, P. and W. H. F. Smith, (1991) Free software helps map and display data, EOS, Trans. AGU, 72, 441.Google Scholar
- Wilson, R., Admire, A., Borrero, J., Dengler, L., Legg, M., Lynett, P., Miller, K., Ritchie, A., Sterling, K., and Whitmore,P. (2012). Observations and Impacts from the 2010 Chilean and 2011 Japanese tsunamis in California. Pure Appl. Geophys. doi:10.1007/s00024-012-0527-z.