Tsunamis are low amplitude, large wavelength waves that can significantly impact coastal regions. Although their destructive impacts are clear from recent events, the frequency with which tsunamis occur is less well constrained. To better understand the tsunami history and coastal impacts in Sri Lanka, this study compares sediments deposited by the December 26, 2004, tsunami to older lagoon sediments in search of evidence for paleotsunami deposits. Results from this study illustrate that the coastal lagoons in Sri Lanka preserve tsunami deposits and can provide the first steps towards constraining the paleotsunami history of the Indian Ocean. Because Sri Lanka is a far field location relative to the Sumatra-Andaman subduction zone, the preserved tsunami deposits are likely mega-tsunami events similar in size and destruction to the December 26, 2004, tsunami. The December 26, 2004, M 9.1?9.3 Sumatra-Andaman earthquake generated a massive tsunami that propagated throughout the Indian Ocean, causing extreme coastal inundation and destruction. The southeastern coastline of Sri Lanka was impacted by the 2004 tsunami where between one and three waves inundated coastal villages, lagoons, and lowlands, killing more than 35,000 people. Karagan Lagoon, located on the southeastern coast of Sri Lanka, was impacted by two waves from this tsunami. Although the lagoon commonly is dominated by organic-rich, siliciclastic clays, silts, and fine sands, the 2004 tsunami deposited a distinct layer of coarse quartz-dominated sand between 1 and 22 cm thick. The base of the 2004 deposit is sharp and erosional and some layers feature faint subparallel laminations. The 2004 tsunami deposit is generally continuous, fines landward, and is confined to the eastern portion of Karagan Lagoon, in the direction from which the tsunami arrived. Sri Lankan lore, in conjunction with reconstructed historical earthquake data, suggests that other tsunamis likely affected Sri Lanka in the past. To test this, twenty-two 1?4 m sediment cores were collected from Karagan Lagoon, providing key information for unraveling the pre-2004 tsunami history of southeastern Sri Lanka. At depth, sixteen cores from Karagan Lagoon contain as many as ten distinct sand layers, including the deposit from the 2004 tsunami. These cores feature siliciclastic clays, silts, and fine sands that dominate the background lagoonal sedimentation that are punctuated by coarse sand layers. These sand-rich layers feature sharp, erosional bases, coarsen and fine upwards, vary in thickness from 1 to 22 cm, and include varying percentages of fine to very coarse sand, with a low-abundance of silt and clay. In the best constrained interval, three coarse sand layers include composition, grain size, grading, and sedimentary structures similar to the sediments deposited by the December 26, 2004, tsunami. The layers are identified in five of the twenty-two cores, although the thicknesses vary. Six additional less well constrained sand layers are present in four of the twenty-two cores. Cores located closer to the lagoon mouth and the eastern coastline (the direction from which the 2004 tsunami arrived) contain more sand layers than cores farther away from the tsunami wave entry point. On the basis of their sedimentary structures, geometry, and extent, these sandy layers are interpreted to represent paleotsunami deposits. AMS radiocarbon dating was used to date the bulk organic sediment from above, between, and below the ten paleotsunami layers in sediment cores from Karagan Lagoon to constrain the timing of events in southeastern Sri Lanka. Material from within the deposit was not dated because it was likely transported from various sources during the event and thus does not represent the age of the tsunami. AMS radiocarbon dates from above and below the paleotsunami layers were calibrated from radiocarbon years before present to calendar years before present (Cal YBP) using OxCal v. 4.0 (Bronk Ramsey, 1995; Bronk Ramsey, 2001) with calibration curve IntCal04 (Reimer et al., 2004). The constraining time intervals of tsunami deposits II?VI were averaged to yield deposits of ages 226, 1641, 4198, 4457, 4924 Cal YBP. Tsunamis VII?X only had sediment dated immediately below the deposit and therefore were deposited prior to 6249, 6455, 6665, and 6840 Cal YBP. In total, ten tsunami deposits, including the 2004 event, are preserved in Karagan Lagoon on the southeastern coast of Sri Lanka. The Karagan Lagoon paleotsunami deposits provide constraints on the recurrence interval of tsunamis similar in magnitude to the 2004 event. The uppermost paleotsunami units were deposited 226, 1641, 4198, 4457, and 4924 Cal YBP, based on AMS radiocarbon dating. Thus, including the 2004 event, six tsunamis affected Karagan Lagoon in the past 5500 years, yielding a recurrence interval of approximately 916 years. Three of the six events, however, occur between ~4000 and 5500 years yielding a recurrence interval of approximately 500 years for this 1500 year period. Four additional older paleotsunami deposits occur in the deeper sections of the cores and were deposited prior to 6249, 6455, 6665, and 6840 Cal YBP, yielding a recurrence interval of approximately 200 years for this time period. Assuming that Karagan Lagoon contains a complete record of tsunami events, the recurrence of tsunamis similar in magnitude to the December 26, 2004, event can occur as often as 200 years. This ?recurrence interval? is illustrated by our data for the time period with increased tsunami activity from ~4000 to 7000 Cal YBP. Tsunamis may potentially affect Sri Lanka at relatively high frequency during certain time intervals though the overall recurrence pattern of these events displays a highly irregular distribution. This extreme variability needs to be taken into consideration when such events are related to earthquake recurrence intervals. Prior to the December 26, 2004, tsunami, paleotsunami deposits in the Indian Ocean were largely unstudied and consequently, Holocene tsunami chronology was incompletely understood for the Indian Ocean. The results from this study represents the first geologic evidence of paleotsunami deposits in Sri Lanka generated by tsunamis during the past 7000 years. The identification of these paleotsunami deposits illustrates that the 2004 tsunami was not a ?one-time event,? but in fact has ancient counterparts.

Thesis (D.P.H.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references (leaves 290-305). / Microfiche. / xix, 305 leaves, bound ill., maps 29 cm

Thesis (M.A. (Health Social Science))--Mahidol University, 2006. / LICL has E-Thesis 0012 ; please contact computer services.

Thesis (M. P.H.M. (Primary Health Care Management))--Mahidol University, 2007. / LICL has E-Thesis 0024 ; please contact computer services.

Memoria (geógrafo) / El riesgo es una condición latente que se ve intensificada por la existencia de población humana, producción e infraestructura, la cual se conjuga con el nivel de vulnerabilidad que estos términos puedan poseer. Por ende, la construcción social del riesgo se produce de manera distinta en función del nivel socioeconómico, cultural y educacional de un determinado grupo social. Si se pretende tipificar la forma en cómo se crea el riesgo por parte de la acción humana, entre las causas más importantes y recurrentes se encuentran: población pobre expulsada de sectores rurales que se ven obligadas a asentarse en sectores inseguros y vulnerables de la ciudad (principalmente zonas periféricas); población de ingresos medios o medios bajos ocupando viviendas regulares situadas en sectores de peligrosidad, que no poseen los sistemas adecuados de mitigación y protección; población de altos recursos que se asientan en áreas de gran valor estético, que teniendo conocimiento del grado de peligrosidad que poseen, las ocupan debido al estatus social y los beneficios en cuanto a paisaje que éstas implican. El estudio de la construcción social el riesgo debe estar destinado a la solución del paradigma conocido como “Gestión de Desastres” el cual debe abordar los esquemas de prevención, respuesta y recuperación de manera integral y debe tener la capacidad de adaptarse a los cambios de la sociedad y a los nuevos desafíos que ésta le impone, como lo es la aparición de nuevas amenazas (LAVELL, 1996). A través de una gestión integral se logra abordar tanto las causas como consecuencias de los desastres socio-naturales, permitiendo con esto la disminución de la vulnerabilidad dado que éste es un factor posible de reducir y modificar. Si bien el Plan Nacional de Emergencia ya lleva más de nueve años de implementación, aún surgen inconvenientes en las etapas de prevención y mitigación, debido al cambio cultural que esto implica, ya que, el nuevo plan asume una labor más exhaustiva en el desarrollo de actividades destinadas a la prevención, preparación y educación de la población para así reducir y aminorar los costos sociales, económicos y de infraestructura que conllevan los escenarios de desastres; cosa muy distinta a la que ocurría con el antiguo programa de protección civil (Plan Nacional de Emergencias de 1977) el cual se centraba sólo en la etapa de post-desastre. El presente estudio busca ahondar y evaluar la construcción social del riesgo al interior de la ciudad de Caldera con el fin de visualizar la capacidad de acción tanto de las autoridades como de la población ordinaria ante un posible evento de tsunami. Además, lo anterior contribuirá a vislumbrar el escenario social y cultural del área de estudio que es, en definitiva, la base de la construcción social del riesgo. / Proyecto Fondecyt 1100223/2010

Strong evidence suggests that the Cascadia subduction zone, off the west coast of Canada and the United States, is strongly seismically-coupled and that a possible megathrust earthquake might occur in that area in the near future. A study of tsunami hazards along the Canadian west coast associated with such a hypothetical earthquake is presented in this report. Numerical simulations of tsunami generation and propagation have been carried out using three models based on shallow water wave theory. Three cases of ground motion representing the ruptures of different crustal segments in the area have been examined. Computed results provide information on tsunami arrival times and a general view of the wave height distribution. The outer coast of Vancouver Island was found to be the most strongly affected area. At the head of Alberni Inlet, wave amplitudes reached up to three times the source magnitude. Inside the Strait of Georgia, the wave heights are significant enough to receive closer attention, especially in low-lying areas. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Magíster en Ciencias, Mención Geofísica / En esta tesis se propone una solución analítica de la ecuación de ondas de agua poco profunda inhomogénea aplicado a problema de deslizamientos de tierra, donde el problema tiene condiciones iniciales nulas. Se desarrollaron tres modelos matemáticos como representantes del movimiento del fondo marino; el primero consiste en una función de variable separable que depende del espacio físico (x) y del tiempo (t), donde la función del tipo gaussiana depende de x y la función tipo caja depende de t. El segundo modelo consiste en una función del tipo caja, esta función mantiene la forma en el tiempo, y se mueve a una velocidad constante sobre un plano inclinado. Este segundo modelo fue la base teórica para desarrollar el tercer y definitivo modelo matemático propuesto por este trabajo, y consiste en una función forzante del tipo parabólica invertida, la cual se mueve a una velocidad constante sobre un plano inclinado. Este tercer modelo mantiene su forma en el tiempo, independiente si se mueve indefinidamente. La solución analítica proveniente de este tercer modelo corresponde a la altura de runup de un tsunami provocado por un deslizamiento de tierra. Esta solución analítica fue comparada con soluciones obtenidas por el método de diferencias finitas y con otros estudios. Todos estos métodos fueron aplicados a los tsunamis generados por deslizamientos de tierra subaéreos en Aguas Calientes y frente a Isla Mentirosa (ambos ocurridos en el Fiordo de Aysén en el año 2007), y también el tsunami provocado por un deslizamiento de tierra submarino ocurrido en Papua Nueva Guinea en el año 1998. Para los eventos del Fiordo de Aysén, se obtuvieron resultados dispares, ya que para el deslizamiento frente a Isla Mentirosa, se sobreestimaron las alturas máximas de runup; y para el deslizamiento de tierra subaéreo de Aguas Calientes se subestimó la altura de runup medida insitu. Sin embargo, debido a la falta de datos y mediciones de campo en el fiordo de Aysén, ambos resultados sirven como valores de referencia para investigaciones futuras. Para el evento de Papua Nueva Guinea, se modelaron dos casos, el primero correspondiente al modelo de playa inclinada de pendiente constante, cuyo ángulo de la pendiente fue tomado de la literatura, el cual es igual a 12°. El segundo modelo también corresponde a un modelo de playa inclinada, donde los datos batimétricos fueron obtenidos de General Bathymetric Chart of the Oceans. La forma de calcular la pendiente fue mediante el método de mínimos cuadrados, cuyo resultado fue de 4,81°. Para ambos modelos se predijeron las alturas de runup medidos insitu, no sin ligeras modificaciones de los parámetros, tales como: el espesor, la velocidad y el largo del deslizamiento de tierra. En este trabajo de tesis se propone que la teoría de los tsunamis generados por impactos de meteoritos sea la base de estudio para investigaciones futuras sobre el fenómeno de los deslizamientos de tierra subaéreos.

El Perú se encuentra ubicado dentro del Cinturón Sísmico del Pacífico, por lo que es una de las zonas sísmicas más activas del mundo. De acuerdo a la teoría de los gaps sísmicos, es muy probable la ocurrencia de un sismo tsunamigenico en la región central del Perú. En esta investigación se propone desarrollar una metodología para obtener la distribución de la fuente sísmica para sismos tsunamigenico a partir de la inversión de formas de onda de tsunami y datos geodésicos. Se plantea las aplicaciones a eventos sísmicos y tsunamis que han afectado el litoral costero peruano. Por ejemplo, el sismo y tsunami de Lima de 1940 (8.0 Mw), el sismo y tsunami de Huacho de 1966 (8.1 Mw), a partir de la inversión de 3 registros mareograficos. El sismo y maremoto de Camaná de 2001 (8.4 Mw) a partir de la inversión combinada de datos mareogr´aficos y geodésicos. El sismo y maremoto de Pisco 2007 (8.0 Mw), a partir de la inversión de datos mareogr´aficos. El sismo y maremoto de Chile 2014 (8.1 Mw) a partir de la inversión combinada de datos mareograficos y geodésicos. Se enfatiza la aplicación de la prueba de confiabilidad para evaluar la resolución y el rango de aplicación de los métodos sísmicos, mareograficos y geodésico. Se ha implementado un procedimiento numérico para el pronóstico de parámetros del tsunami (máxima altura y tiempo de arribo) a partir de una base de datos de fuentes sísmicas unitarias pre-simuladas. Los resultados de esta investigación permitirán obtener la distribución de las asperezas (zonas de mayor liberación de energía sísmica), lo cual permitirá desarrollar planes de prevención, previsión y mitigación de desastres por fenómenos naturales. / Tesis

Seismic hazard analysis is concerned with estimating risk to human populations due to earthquakes and the other natural disasters that they cause. In many parts of the world, earthquake-generated tsunamis are especially dangerous. Assessing the risk for seismic disasters relies on historical data that indicate which fault zones are capable of supporting significant earthquakes. Due to the nature of geologic time scales, the era of seismological data collection with modern instruments has captured only a part of the Earth's seismic hot zones. However, non-instrumental records, such as anecdotal accounts in newspapers, personal journals, or oral tradition, provide limited information on earthquakes that occurred before the modern era. Here, we introduce a method for reconstructing the source earthquakes of historical tsunamis based on anecdotal accounts. We frame the reconstruction task as a Bayesian inference problem by making a probabilistic interpretation of the anecdotal records. Utilizing robust models for simulating earthquakes and tsunamis provided by the software package GeoClaw, we implement a Metropolis-Hastings sampler for the posterior distribution on source earthquake parameters. In this work, we present our analysis of the 1852 Banda Arc earthquake and tsunami as a case study for the method. Our method is implemented as a Python package, which we call tsunamibayes. It is available, open-source, on GitHub: https://github.com/jwp37/tsunamibayes.

Numerous observations suggest that the elastic description of the subduction earthquake cycles is incomplete. Micro-seismicity is recorded in active margins that are believed to be locked, while peculiar extensional earthquakes occur in convergent plate boundaries following tsunami earthquakes. The morphology of active margins, which evolves on time scales of 100s of kyr, shows similarities to ongoing deformation documented over 10–100 yrs and the coastal domains of Cascadia, Chile, and other subduction zones record long-term uplift. Lastly, the very threshold where faults break and earthquake nucleate has been vigorously debated for years. In this thesis, I combine various geophysical tools to study short- and long-term processes and learn how their interplay can shape the deformation field imparted by earthquake cycles, mainly in the upper plate of subduction zones. In the first chapter, I analyze surface heat flow measurements taken in the proximity of the southern Dead Sea fault to demonstrate its friction is 0.27±0.17. In the second chapter, I compute an updated horizontal and vertical GNSS velocity field for Bangladesh, Myanmar, and adjacent regions. I show that the Kabaw fault, which lies east of the primary thrust system, is accommodating shortening that was initially attributed to the main thrust and demonstrate that the Indo-Burma subduction is locked, converging, and capable of hosting great megathrust events. In the third chapter, I use thermomechanical models to show that reducing the dip angle of a subducting slab, on a timescale of millions of years, can result in extensional fault failure above a megathrust earthquake on timescales of seconds to months. In the fourth chapter, I demonstrate how the buildup of interseismic elastic stresses brings sections of the forearc into compressional failure, which yields irreversible uplift of the coastal domain per evidence from Chile. Finally, I argue that combining short- and long-term processes into subduction zone models can better mitigate tsunami and earthquake hazards. I show how long-term reduction of slab dip angle could culminate in devastating tsunamis. I argue that the collection of long-term uplift records of upper plates or volcanic arc migration can constrain slab dip changes and so may identify areas with increased tsunami potential. In addition, upper plate irreversible deformation should be introduced to earthquake rupture models as these may hold significant implications for understanding and mitigating earthquake hazards.