The west coast of North America faces the risk of tsunamis generated by seismic rupture in three regions, namely, the Cascadia subduction zone extending from southwestern British Columbia to northern California, the southern Queen Charlotte margin in the Haida Gwaii area, and the Winona Basin just northeast of Vancouver Island. In this thesis, I construct tsunamigenic rupture models with a 3-D elastic half-space dislocation model for these three regions. The tsunami risk is the highest along the Cascadia coast, and many tsunami source models have been developed and used in the past. In efforts to improve the Cascadia tsunami hazard assessment, I use an updated Cascadia fault geometry to create 9 tsunami source models which include buried, splay-faulting, and trench-breaching rupture. Incorporated in these scenarios is a newly-proposed splay fault based on minor evidence found in seismic reflection images off Vancouver Island. To better understand potential rupture boundaries of the Cascadia megathrust rupture, I also model deformation caused by the 1700 C.E. great Cascadia earthquake that fit updated microfossil-based paleoseismic coastal subsidence estimates. These estimates validate the well-accepted along-strike heterogenic rupture of the 1700 earthquake but suggest greater variations in subsidence along the coast. It is recognized that the Winona Basin area just north of the Cascadia subduction zone may have the potential to host a tsunamigenic thrust earthquake, but it has not been formally included in tsunami hazard assessments. There is a high degree of uncertainty in the tectonics of the area, the presence of a subduction “megathrust”, fault geometry, and rupture boundaries. Assuming worst-case scenarios and considering the uncertainties, I construct a fault geometry using seismic images and generate six tsunami sources with buried and trench-breaching rupture in which downdip rupture extent is varied. The Mw 7.8 2012 Haida Gwaii earthquake and its large tsunami demonstrated the presence of a subduction megathrust and its capacity of hosting tsunamigenic rupture, but little has been done to include future potential thrust earthquakes in the Haida Gwaii region in tsunami hazard assessment. To fill this knowledge gap, I construct a new megathrust geometry using seismic reflection images and receiver-function results and produce nine tsunami sources for Haida Gwaii, which include buried and trench-breaching ruptures. In the strike direction, the scenarios include long ruptures from mid-way between Haida Gwaii and Vancouver Island to mid-way between Haida Gwaii and the southern tip of Alaskan Panhandle, and shorter rupture scenarios north and south of the main rupture of the 2012 earthquake. For all the tsunami source and paleoseismic scenarios, I also calculate stress drop along the fault. Comparison of the stress drop results with those of real megathrust earthquakes worldwide indicates that these models are mechanically realistic. / Graduate

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20323号 / 工博第4260号 / 新制||工||1660(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 間瀬 肇, 教授 平石 哲也, 准教授 森 信人 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Accurate prediction of tsunami waves requires complete boundary and initial condition data, coupled with the appropriate mathematical model. However, necessary data is often missing or inaccurate, and may not have sufficient resolution to capture the dynamics of such nonlinear waves accurately. In this thesis we demonstrate that variational data assimilation for the continuous shallow water equations (SWE) is a feasible approach for recovering both initial conditions and bathymetry data from sparse observations. Using a Sadourny finite-difference finite volume discretisation for our numerical implementation, we show that convergence to true initial conditions can be achieved for sparse observations arranged in multiple configurations, for both isotropic and anisotropic initial conditions, and with realistic bathymetry data in two dimensions. We demonstrate that for the 1-D SWE, convergence to exact bathymetry is improved by including a low-pass filter in the data assimilation algorithm designed to remove scale-scale noise, and with a larger number of observations. A necessary condition for a relative L2 error less than 10% in bathymetry reconstruction is that the amplitude of the initial conditions be less than 1% of the bathymetry height. We perform Second Order Adjoint Sensitivity Analysis and Global Sensitivity Analysis to comprehensively assess the sensitivity of the surface wave to errors in the bathymetry and perturbations in the observations. By demonstrating low sensitivity of the surface wave to the reconstruction error, we found that reconstructing the bathymetry with a relative error of about 10% is sufficiently accurate for surface wave modelling in most cases. These idealised results with simplified 2-D and 1-D geometry are intended to be a first step towards more physically realistic settings, and can be used in tsunami modelling to (i) maximise accuracy of tsunami prediction through sufficiently accurate reconstruction of the necessary data, (ii) attain a priori knowledge of how different bathymetry and initial conditions can affect the surface wave error, and (iii) provide insight on how these can be mitigated through optimal configuration of the observations. / Thesis / Candidate in Philosophy

This report focuses on using the Papathoma Tsunami Vulnerability Assessment Model (PTVA) to demonstrate the vulnerability of Cayucos to a 500-year tsunami, and using the results to inform specific planning recommendations. By modeling inundation with GIS and analyzing building attributes via the PTVA model, this study has gone beyond any previous vulnerability assessments of Cayucos. Findings include: delineation of the most vulnerable areas, estimates of numbers of lost civic buildings, commercial buildings and houses, as well as estimates of people displaced from tsunami damaged homes. The report goes on to discuss what mitigation measures are in place and what further specific steps could be taken to ensure the long term sustainability of the town and help reduce future tsunami losses. Cayucos is a small coastal town in San Luis Obispo County, California; popular with tourists and locals for its beach, pier, and downtown. Intense coastal development and low lying topography makes Cayucos among the most tsunami vulnerable communities in the county. Many civic and economically important buildings, as well as homes, are within the 500-year tsunami inundation area. In the absence of fully developed, and accessible assessment tools like FEMA’s HAZUS tsunami program; local planners have had only basic information to assess the community’s tsunami vulnerability. The Papathoma Tsunami Vulnerability Assessment Model (PTVA) is a method that uses available tsunami runup estimations and field data collection to produce a detailed assessment of individual building survivability and overall community vulnerability.

No / Digital content is increasingly pervasive. Communication technologies enable the creation and dissemination of content on a transnational basis. However, the relationship between communication technology and society is complex and is impacted both by the requirements of the communicator and also cultural and social norms associated with the context of the user. How does digital technology influence media communication? How far does media communication transcend technology? The boundaries between the various forms of formal communication and social communication are blurring and the user is no longer just a consumer or someone who interacts with information; they are also a creator of new information. Companies with commercial interests in these areas are seeking to exploit new forms of communication without alienating the user.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23852号 / 工博第4939号 / 新制||工||1771(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 森 信人, 教授 平石 哲也, 准教授 志村 智也 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Tsunamis and storms are the most devastating coastal hazards that can cause great loss of life and infrastructure damage. To assess tsunami and storm hazard, the magnitude and frequency of each type of event are needed. However, major tsunamis and storms are very infrequent, especially tsunamis, and the only reliable record is the deposits they leave behind. Tsunami and storm deposits can be used to calculate the magnitudes of the respective event, and to contribute to the hazard frequency where there is no historical records. Therefore, for locations where both events could occur, it is crucial to differentiate between the two types of events. Existing studies on the similarities and differences between the two types of deposits all suffer from paucity of the number of events and field data, and a wide range of initial conditions, and thus an unequivocal set of distinguishing deposit characteristics has not been identified yet. In this study, we aim to tackle the problem with the MEso-SCAle Particle Transport model (MESCAPT) that combines the advantages of concentration-based Eulerian methods and particle-based method. The advantage of the former is efficiency and the latter is detailed sediment transport and deposit information. Instead of modeling individual particles, we assume that a group of sediment grains travel and deposit together, which is called a meso-scale particle. This allows simulation domains that are large enough for tsunami and storm wave propagation and inundation. The sediment transport model is coupled with a hydrodynamic model based on the shallow water equations. Simulation results of a case study show good agreements with field measurements of deposits left behind by the 2004 Indian Ocean Tsunami. Idealized tsunami and storm case studies demonstrate the model's capabilities of reproducing morphological changes, as well as microscopic grain-size trends. / Ph. D.

Yes / Around 8150 BP, the Storegga tsunami struck North-west Europe. The size of this wave has led many to assume that it had a devastating impact upon contemporaneous Mesolithic communities, including the final inundation of Doggerland, the now submerged Mesolithic North Sea landscape. Here, the authors present the first evidence of the tsunami from the southern North Sea, and suggest that traditional notions of a catastrophically destructive event may need rethinking. In providing a more nuanced interpretation by incorporating the role of local topographic variation within the study of the Storegga event, we are better placed to understand the impact of such dramatic occurrences and their larger significance in settlement studies. / The study was supported by European Research Council funding through the European Union's Horizon 2020 research and innovation programme (project 670518 LOST FRONTIERS, https://erc.europa.eu/ https://lostfrontiers.teamapp.com/) and the Estonian Research Council grant (https://www.etag.ee; project PUTJD829).

På Kanarieön La Palma finns sprickzonen och vulkanen Cumbre Vieja. Under ett vulkanutbrott år 1949 bildades ett förkastningssystem längs vulkanens västra sida som skulle kunna vara ett förstadium till en framtida kollaps av vulkanen. Denna kollaps skulle kunna leda till bildandet av en tsunami när kollapsmaterial rasar ner i havet likt ett jordskred. Tsunamin kan komma att spridas över stora delar av Atlanten och i olika grad påverka de omkringliggande kontinenterna. Det finns olika teorier om hur stort jordskredet kommer att bli och om det kommer att ske successivt eller kollapsa som en enda enhet. I detta arbete studeras fyra kollapsscenarier med volymer av 20 km3, 40 km3, 80 km3 och 450 km3 närmare. Utifrån dessa volymer skapas riskanalyskartor i GIS över ön Teneriffa och New Yorks storstadsområde som visar hur långt över land tsunamin når vid de olika kollapsscenarierna. Dessa kartor jämförs sedan med markanvändningskartor över Teneriffa och New Yorks storstadsområde. Trots att tsunamivågen kan bli mycket hög vid Teneriffas kust kommer stora delar av ön att undkomma tsunamin, vilket bl.a. beror på öns höga höjd över havet. Då de flesta byggnader är belägna vid kusten innebär det att många människor ändå riskerar att drabbas. New Yorks storstadsområde är istället lågt beläget, vilket bidrar till att många kustnära områden kommer att drabbas trots att våghöjden har avtagit väsentligt. Då detta område är mycket tätbefolkat kan en tsunami därför leda till en stor påverkan. / On the Canary Island La Palma there is a volcanic ridge called Cumbre Vieja. During an eruption in 1949 a fault system was formed along the western flank of the volcano that can be an early stage of a future flank collapse of Cumbre Vieja. During this collapse a large volume of rock material will fall into the ocean like a landslide, which could lead to the formation of a tsunami. The tsunami could spread over large parts of the Atlantic Ocean and to varying extent affect the surrounding continents. There are different theories of how big the landslide will be and if it will collapse gradually or as a coherent block. In this study four collapse scenarios with different volumes, 20 km3, 40 km3, 80 km3 and 450 km3, are studied more closely. Based on these volumes, vulnerability maps are created in GIS covering the island Tenerife and the New York metropolitan area. The maps show the land reach of the tsunami for each of the collapse scenarios. These maps are thereafter compared with land use maps over Tenerife and the New York metropolitan area. Despite the high amplitude of the tsunami wave at the coast of Tenerife, large parts of the island will remain unaffected by the tsunami. This is due to, among other things, the high altitude of the island. However, most buildings are located along the coast, which means that many people are at risk. The New York metropolitan area has, on the other hand, low altitude which is one explanation why many coastal areas will be affected despite the significant decrease in tsunami wave height. A tsunami would have a major impact due to these areas being densely populated.

Tsunami concerns have increased in the world after the 2004 Indian Ocean tsunami and the 2011 Tohoku tsunami. Consequently, tsunami models have been developed rapidly in the last few years. One of the advanced tsunami models is the GeoClaw tsunami model introduced by LeVeque (2011). This model is adaptive and consistent. Because of different sources of uncertainties in the model, observations are needed to improve model prediction through a data assimilation framework. Model inputs are earthquake parameters and topography. This thesis introduces a real-time tsunami forecasting method that combines tsunami model with observations using a hybrid ensemble Kalman filter and ensemble Kalman smoother. The filter is used for state prediction while the smoother operates smoothing to estimate the earthquake parameters. This method reduces the error produced by uncertain inputs. In addition, state-parameter EnKF is implemented to estimate earthquake parameters. Although number of observations is small, estimated parameters generates a better tsunami prediction than the model. Methods and results of prediction experiments in the Red Sea are presented and the prospect of developing an operational tsunami prediction system in the Red Sea is discussed.