Tsunamis and Tsunami Sedimentology

Sugawara, Daisuke; Minoura, Koji; Imamura, Fumihiko

doi:10.1016/b978-0-444-51552-0.00003-5

Cited by 46 publications

(66 citation statements)

References 56 publications

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“…Este evento natural ha sido definido como un movimiento temporal de onda generado por la perturbación súbita o desplazamiento vertical de un gran volumen de agua, ya sea en el océano o en cuencas (semi-) cerradas (Sugawara et al, 2008). La onda generada por un tsunami se propaga concéntricamente en la cuenca, a velocidades de hasta 800 km/h, casi imperceptibles en alta mar (rara vez > 1 m de altura y períodos de kilómetros de distancia).…”

Section: La Importancia De La Evidencia Paleo-tsunamigénicaunclassified

“…Cuando un tsunami llega a la costa, su velocidad disminuye (aún siendo superior a las de olas generadas por el viento), pero su amplitud se incrementa dramáticamente ya que su energía de flujo (la cual depende de su velocidad y altura) se mantiene casi constante. Por consiguiente, al entrar en aguas costeras más someras, la altura del tsunami crece progresivamente debido a la reducción de la profundidad, produciendo una pared de agua de hasta decenas o centenares de metros de alto, proporcional al volumen de agua desplazado en el punto de origen, que tiene que acomodarse al contexto espacial de la cuenca costera, con todas sus restricciones geomorfológicas, batimétricas, topográficas y geográficas (Sugawara et al, 2008). La ola resultante penetra cientos de kilómetros tierra adentro, inundando temporalmente la zona costera (hasta decenas de metros de altura), generando evidencias tanto geomorfológicas como sedimentarias, provocando así tanto erosión severa, como depositación y cambios geográficos en la línea de costa, sumados al gran impacto, daño severo y destrucción de la región afectada.…”

Section: La Importancia De La Evidencia Paleo-tsunamigénicaunclassified

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Marco Conceptual Para Investigaciones Tsunamigénicas: Caso Litoral Pacífico Colombiano

Velasco

López

2016

revbol

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Forma de citar:Velasco, E.R., y López, G.I. 2016. Marco conceptual para investigaciones tsunamigénicas: caso litoral Pacífico colombiano. Boletín de Geología, 38(4): 79-106. RESUMENA nivel histórico, la Costa Pacífica Colombiana ha presenciado seis tsunamis en los últimos 130 años, de los cuales dos han ocasionado completa destrucción de algunos municipios y provocado víctimas humanas. El presente trabajo pretende dar las bases conceptuales necesarias para abordar investigaciones focalizadas a la caracterización de la amenaza por tsunami, verificar el estado del arte y determinar las necesidades investigativas futuras. Toda adecuada realización de investigaciones en paleo-tsunamis debe ser multi-disciplinaria, y compilar, obtener y analizar información geológica, geomorfológica, biológica, antropológica, arqueológica e histórica, lo más detallada posible. Hasta el momento en Colombia, los trabajos realizados en torno a tsunamis han estado enfocados a la cuantificación de la inundación en localidades como Tumaco y Buenaventura. No obstante, a lo largo de la Costa Pacífica Colombiana aún no se ha trabajado en la identificación y caracterización de las fuentes de tsunami, búsqueda y caracterización de evidencias físicas de eventos pasados (e.g. depósitos de paleo-tsunamis), microzonificación sísmica regional, cambios en patrones de vegetación por eventos extremos o el impacto a la dinámica de comunidades indígenas antiguas por tsunamis, entre otros. Para que la gestión del riesgo sea efectiva, deben generarse mapas de amenaza por tsunami que integren todas las herramientas y disciplinas que identifiquen y caractericen dicha amenaza. Por ende, aquí se proponen los pasos a seguir para adecuadas investigaciones tsunamigénicas.Palabras clave: paleo-tsunamis, depósitos de tsunamis, paleo-sismología, Pacífico Colombiano, Zona de Subducción de Nazca. CONCEPTUAL FRAMEWORK FOR TSUNAMIGENIC RESEARCH: COLOMBIAN PACIFIC COAST CASE STUDY ABSTRACTHistorically, the Colombian Pacific Coast has witnessed six tsunamis in the past 130 years, two of which have caused complete community destruction and human loss. The present paper aims to provide a conceptual framework needed to approach palaeo-tsunami research in the area, verifying the state of the art of tsunami hazard characterization and identifying any future investigations. Any acceptable palaeo-tsunami investigation should be multi-disciplinary, and compile, acquire and analyze in much detail, geological, geomorphological, biological, anthropological, archaeological and historical information. So far, the only research done related to tsunami hazard has been for the coastal cities of Tumaco and Buenaventura, and it has been focused on quantification of tsunami flooding. However, no research has yet been done on the identification and characterization of tsunami sources, exploration and characterization of the physical evidence of past events (e.g. palaeo-tsunami deposits), seismic micro-zonation, regional changes in vegetation patterns resulting from extreme events, or changes...

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Section: La Importancia De La Evidencia Paleo-tsunamigénicaunclassified

Marco Conceptual Para Investigaciones Tsunamigénicas: Caso Litoral Pacífico Colombiano

Velasco

López

2016

revbol

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“…In spite of that, we report land subsidence estimates from areas where this phenomena affected vast zones. Local measurements of tsunami heights were conducted in areas directly exposed to the open ocean (Sugawara et al, 2008). We observed the highest pervasive marks left by vegetation razed by the tsunami, traces of erosion on the beach and supralittoral zones, sand and boulder deposits, and destruction provoked by the tsunami (Fig.…”

Section: Coastal Uplift and Tsunami Heights Measurementsmentioning

confidence: 99%

Levantamiento cosismico e impacto del tsunami a lo largo de la costa de Chile central asociado al terremoto del Maule Mw8,8 de 2010.

Vargas¹,

Farías²,

Carretier³

et al. 2011

Andgeo

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ABSTrACT. On February 27, 2010 at 03:34:08 AM an Mw8.8 earthquake, with epicenter located off Cobquecura (73.24°W; 36.29°S), severely hit Central Chile. The tsunami waves that followed this event affected the coastal regions between the cities of Valparaíso and Valdivia, with minor effects as far as Coquimbo. The earthquake occurred along the subduction of the Nazca oceanic plate beneath the South American plate. Coseismic coastal uplift was estimated through observations of bleached lithothamnioids crustose coralline algae, which were exposed after the mainshock between 34.13°S and 38.34°S, suggesting the latitudinal distribution of the earthquake rupture. The measured coastal uplift values varied between 240±20 cm at sites closer to the trench along the western coast of the Arauco peninsula and 15±10 cm at sites located farther east. A maximum value of 260±50 cm was observed at the western coast of Santa María Island, which is similar to the reported uplift associated with the 1835 earthquake at Concepción. Land subsidence values on the order of 0.5 m to 1 m evidenced a change in polarity and position of the coseismic hinge at 110-120 km from the trench. In four sites along the coast we observed a close match between coastal uplift values deduced from bleached lithothamnioids algae and GPS measurements. According to field observations tsunami heights reached ca. 14 m in the coastal area of the Maule Region immediately north of the epicenter, and diminished progressively northwards to 4-2 m near Valparaíso. Along the coast of Cobquecura, tsunami height values were inferior to 2-4 m. More variable tsunami heights of 6-8 m were measured at Dichato-Talcahuano and Tirúa-Puerto Saavedra, in the Biobío and Arauco regions, respectively, to the south of the epicenter. According to eyewitnesses, the tsunami reached the coast between 12 to 20 and 30 to 45 minutes in areas located closer and faraway from the earthquake rupture zone, respectively. Destructive tsunami waves arrived also between 2.5 and 4.5 hours after the mainshock, especially along the coast of the Biobío and Arauco regions. The tsunami effects were highly variable along the coast, as a result of geomorphological and bathymetric local conditions, besides potential complexities induced by the main shock. ; 36,29°S), afectó severamente la zona centrosur de Chile. Posteriormente un tsunami afectó las costas comprendidas entre las regiones de Valdivia y Valparaíso, con efectos menores en la costa de Coquimbo. El terremoto ocurrió a lo largo de la subducción de la placa tectónica de Nazca bajo la placa Sudamericana. Se estimó el levantamiento cosísmico de la costa a partir de observaciones de la franja de algas coralina lithothamnioideas, expuesta como producto del terremoto. Evidencias de deformación vertical se observaron entre los 34,13°S y 38,34°S, sugiriendo la extensión latitudinal de la ruptura sísmica del evento principal. El levantamiento costero observado varió entre 240±20 cm, en la costa occidental de la península de Arauco, ubicada relativamente má...

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“…Moreover, none of the numerous post-tsunami surveys conducted during the last decade reported the deposition of similar, spatially confined ridges (e.g., Scoffin, 1993;Morton et al, 2008;Etienne et al, 2011;Goto et al, 2012). Considering the different hydrodynamic processes associated with storm and tsunami inundation a tsunamigenic emplacement of coarse-clast ridges is unlikely (e.g., Sugawara et al, 2008;Weiss, 2012). Hence, combining field evidence for recent storms and the related hydrodynamic aspects, coral-rubble ridges are most probably the result of storm wave action (e.g., Baines and McLean, 1976;Morton et al, 2006Morton et al, , 2008Spiske and Jaffe, 2009).…”

Section: Spiske and R B Halley: A Coral-rubble Ridge As Evidencementioning

confidence: 99%

A coral-rubble ridge as evidence for hurricane overwash, Anegada (British Virgin Islands)

Spiske¹,

Halley

2014

Adv. Geosci.

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Abstract.A coral-rubble ridge fringes part of the north shore of Anegada, a low-lying island in the northern Caribbean. Both historical reports and the geological record underline its vulnerability to tsunami and hurricanes. In this study we document the sedimentary characteristics of a coral-rubble ridge, which extends discontinuously along 1.5-1.8 km of chiefly north-facing shores at Soldier Wash. The ridge is less distinctive and appears only in patches along the west-facing shoreline at Windless Bight, where the wave regime is calmer. It is located ca. 8 m from the fair-weather shore, has a maximum width of 15 m and a maximum thickness of 0.8 m. The lower seaward-facing slope of the ridge is relatively flat, probably due to successive reworking, whereas the upper seaward slope is steep and partly displays avalanching faces. The landward flank is gently sloping and terminates abruptly. The ridge is mainly composed of well-rounded, encrusted and bored coral rubble (average diameter of 16 cm) that has been reworked in the shallow marine environment prior to transport. Only a few pieces of angular beach rock and karstified Pleistocene limestone are incorporated. The components build a clast-supported framework. No sand is present in the interstices. Imbrication of flat clasts indicates a deposition during landward bed load transport. The ridge morphology, composition and related hydrodynamic conditions during its emplacement are typical for coral-rubble ridges deposited by hurricane-induced storm surges. In comparison, nearby evidence for tsunami inundation is very different because the tsunami-transported coral boulders on Anegada are much bigger (2 m) than the biggest components in the ridge, they are deposited much farther inland (up to 1.5 km), and the corals seem to have been freshly broken out of the reef by the tsunami.The age of the ridge is difficult to estimate. The dark grey surface of the ridge is caused by bioweathering by endolithic organisms that takes tens of years and may give a very rough estimate of the minimum age of the ridge.Storms and related surges that built the ridge were likely stronger than 2010 hurricane Earl, which attained category 4 north of the island. Earl was able to slightly rework the lower seaward part of the ridge, but transported only few and smaller pieces of coral rubble and sand onshore. Therefore, the coral-rubble ridge found at the north shore of Anegada may imply that the island is vulnerable to hurricane-induced surges of greater impact (in relation to storm path and intensity) compared with the any of the recently documented storms which were only able to rework the ridge.

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Tsunamis and Tsunami Sedimentology

Cited by 46 publications

References 56 publications

Marco Conceptual Para Investigaciones Tsunamigénicas: Caso Litoral Pacífico Colombiano

Marco Conceptual Para Investigaciones Tsunamigénicas: Caso Litoral Pacífico Colombiano

Levantamiento cosismico e impacto del tsunami a lo largo de la costa de Chile central asociado al terremoto del Maule Mw8,8 de 2010.

A coral-rubble ridge as evidence for hurricane overwash, Anegada (British Virgin Islands)

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