Local variation of inundation, sedimentary characteristics, and mineral assemblages of the 2011 Tohoku-oki tsunami on the Misawa coast, Aomori, Japan

NASA Astrophysics Data System (ADS)

Nakamura, Yugo; Nishimura, Yuichi; Putra, Purna Sulastya

2012-12-01

The 2011 Tohoku-oki tsunami caused severe damage to the coastal regions of eastern Japan and left a sediment veneer over affected areas. We discuss differences in depositional characteristics of the 2011 Tohoku-oki tsunami from the viewpoint of the sediment source, coastal topography and flow height. The study area on the Misawa coast, northern Tohoku, includes a 20 km long coastline with sandy beaches, coastal dunes and a gently sloping lowland. This landscape assemblage provides an opportunity to examine the effects of topography on the characteristics of the tsunami deposit. During field surveys conducted from April 10 to May 2, 2011, we described the thickness, facies, and structure of the tsunami deposit. We also collected sand samples at approximately 20 m intervals along 13 shore-perpendicular transects extending up to 550 m inland, for grain size and mineral assemblage analysis. The tsunami flow height was estimated by measuring the elevation of debris found in trees, broken tree limbs, or water marks on buildings. The nature of the coastal lowland affected the flow height and inundation distance. In the southern part of the study area, where there is a narrow, 100 m wide low-lying coastal strip, the run-up height reached 10 m on the landward terrace slopes. To the north, the maximum inundation reached 550 m with a run-up height of 3.2 m on the wider, low-lying coastal topography. The average flow height was 4-5 m. The tsunami eroded coastal dunes and formed small scarps along the coast. Immediately landward of the coastal dunes the tsunami deposit was more than 20 cm thick, but thinned markedly inland from this point. Close to the dunes the deposit was composed largely of medium sand (1-2 Φ) with planar and parallel bedding, but with no apparent upward fining or coarsening. The grain size was similar to that of the coastal dune and we infer that the dunes were the local source material for the tsunami deposit at this point. The mineral assemblage of the tsunami deposit was dominated by orthopyroxene and clinopyroxene and was also similar to the dune and beach sand. At sites more than half the inundation distance inland, the thinner tsunami deposit consisted mainly of fine sand (2.375 Φ) with some upward fining. The difference in grain size and sedimentary characteristics was probably caused by differences in sediment transportation and depositional processes. We infer that the well-sorted, finer sediments were deposited out of suspension, whereas the relatively coarse sands were laid down from traction flows. The depositional characteristics of the 2011 Tohoku-oki tsunami deposit appeared to have been affected mainly by the coastal topography and the extent of erosion at any one point, as opposed to flow height.

Numerical simulation of tsunami generation by cold volcanic mass flows at Augustine Volcano, Alaska

USGS Publications Warehouse

Waythomas, C.F.; Watts, P.; Walder, J.S.

2006-01-01

Many of the world's active volcanoes are situated on or near coastlines. During eruptions, diverse geophysical mass flows, including pyroclastic flows, debris avalanches, and lahars, can deliver large volumes of unconsolidated debris to the ocean in a short period of time and thereby generate tsunamis. Deposits of both hot and cold volcanic mass flows produced by eruptions of Aleutian arc volcanoes are exposed at many locations along the coastlines of the Bering Sea, North Pacific Ocean, and Cook Inlet, indicating that the flows entered the sea and in some cases may have initiated tsunamis. We evaluate the process of tsunami generation by cold granular subaerial volcanic mass flows using examples from Augustine Volcano in southern Cook Inlet. Augustine Volcano is the most historically active volcano in the Cook Inlet region, and future eruptions, should they lead to debris-avalanche formation and tsunami generation, could be hazardous to some coastal areas. Geological investigations at Augustine Volcano suggest that as many as 12-14 debris avalanches have reached the sea in the last 2000 years, and a debris avalanche emplaced during an A.D. 1883 eruption may have initiated a tsunami that was observed about 80 km east of the volcano at the village of English Bay (Nanwalek) on the coast of the southern Kenai Peninsula. Numerical simulation of mass-flow motion, tsunami generation, propagation, and inundation for Augustine Volcano indicate only modest wave generation by volcanic mass flows and localized wave effects. However, for east-directed mass flows entering Cook Inlet, tsunamis are capable of reaching the more populated coastlines of the southwestern Kenai Peninsula, where maximum water amplitudes of several meters are possible.

2011 Tohoku tsunami runup hydrographs, ship tracks, upriver and overland flow velocities based on video, LiDAR and AIS measurements

NASA Astrophysics Data System (ADS)

Fritz, H. M.; Phillips, D. A.; Okayasu, A.; Shimozono, T.; Liu, H.; Takeda, S.; Mohammed, F.; Skanavis, V.; Synolakis, C.; Takahashi, T.

2014-12-01

The 2004 Indian Ocean tsunami marked the advent of survivor videos mainly from tourist areas in Thailand and basin-wide locations. Near-field video recordings on Sumatra's north tip at Banda Aceh were limited to inland areas a few kilometres off the beach (Fritz et al., 2006). The March 11, 2011, magnitude Mw 9.0 earthquake off the Tohoku coast of Japan caused catastrophic damage and loss of life resulting in the costliest natural disaster in recorded history. The mid-afternoon tsunami arrival combined with survivors equipped with cameras on top of vertical evacuation buildings provided numerous inundation recordings with unprecedented spatial and temporal resolution. High quality tsunami video recording sites at Yoriisohama, Kesennuma, Kamaishi and Miyako along Japan's Sanriku coast were surveyed, eyewitnesses interviewed and precise topographic data recorded using terrestrial laser scanning (TLS). The original video recordings were recovered from eyewitnesses and the Japanese Coast Guard (JCG). The analysis of the tsunami videos follows an adapted four step procedure (Fritz et al., 2012). Measured overland flow velocities during tsunami runup exceed 13 m/s at Yoriisohama. The runup hydrograph at Yoriisohama highlights the under sampling at the Onagawa Nuclear Power Plant (NPP) pressure gauge, which skips the shorter period second crest. Combined tsunami and runup hydrographs are derived from the videos based on water surface elevations at surface piercing objects and along slopes identified in the acquired topographic TLS data. Several hydrographs reveal a draw down to minus 10 m after a first wave crest exposing harbor bottoms at Yoriisohama and Kamaishi. In some cases ship moorings resist the main tsunami crest only to be broken by the extreme draw down. A multi-hour ship track for the Asia Symphony with the vessels complete tsunami drifting motion in Kamaishi Bay is recovered from the universal ship borne AIS (Automatic Identification System). Multiple hydrographs corroborate the tsunami propagation through Miyako Bay and up the Hei River. Tsunami outflow currents up to 11 m/s were measured in Kesennuma Bay making navigation impossible. Further we discuss the complex effects of coastal structures on inundation and outflow hydrographs as well as associated flow velocities.

Physical criteria for distinguishing sandy tsunami and storm deposits using modern examples

USGS Publications Warehouse

Morton, Robert A.; Gelfenbaum, Guy; Jaffe, Bruce E.

2007-01-01

Modern subaerial sand beds deposited by major tsunamis and hurricanes were compared at trench, transect, and sub-regional spatial scales to evaluate which attributes are most useful for distinguishing the two types of deposits. Physical criteria that may be diagnostic include: sediment composition, textures and grading, types and organization of stratification, thickness, geometry, and landscape conformity. Published reports of Pacific Ocean tsunami impacts and our field observations suggest that sandy tsunami deposits are generally 30 cm thick, generally extend The distinctions between tsunami and storm deposits are related to differences in the hydrodynamics and sediment-sorting processes during transport. Tsunami deposition results from a few high-velocity, long-period waves that entrain sediment from the shoreface, beach, and landward erosion zone. Tsunamis can have flow depths greater than 10 m, transport sediment primarily in suspension, and distribute the load over a broad region where sediment falls out of suspension when flow decelerates. In contrast, storm inundation generally is gradual and prolonged, consisting of many waves that erode beaches and dunes with no significant overland return flow until after the main flooding. Storm flow depths are commonly

NOAA Propagation Database Value in Tsunami Forecast Guidance

NASA Astrophysics Data System (ADS)

Eble, M. C.; Wright, L. M.

2016-02-01

The National Oceanic and Atmospheric Administration (NOAA) Center for Tsunami Research (NCTR) has developed a tsunami forecasting capability that combines a graphical user interface with data ingestion and numerical models to produce estimates of tsunami wave arrival times, amplitudes, current or water flow rates, and flooding at specific coastal communities. The capability integrates several key components: deep-ocean observations of tsunamis in real-time, a basin-wide pre-computed propagation database of water level and flow velocities based on potential pre-defined seismic unit sources, an inversion or fitting algorithm to refine the tsunami source based on the observations during an event, and tsunami forecast models. As tsunami waves propagate across the ocean, observations from the deep ocean are automatically ingested into the application in real-time to better define the source of the tsunami itself. Since passage of tsunami waves over a deep ocean reporting site is not immediate, we explore the value of the NOAA propagation database in providing placeholder forecasts in advance of deep ocean observations. The propagation database consists of water elevations and flow velocities pre-computed for 50 x 100 [km] unit sources in a continuous series along all known ocean subduction zones. The 2011 Japan Tohoku tsunami is presented as the case study

Tsunami Simulators in Physical Modelling - Concept to Practical Solutions

NASA Astrophysics Data System (ADS)

Chandler, Ian; Allsop, William; Robinson, David; Rossetto, Tiziana; McGovern, David; Todd, David

2017-04-01

Whilst many researchers have conducted simple 'tsunami impact' studies, few engineering tools are available to assess the onshore impacts of tsunami, with no agreed methods available to predict loadings on coastal defences, buildings or related infrastructure. Most previous impact studies have relied upon unrealistic waveforms (solitary or dam-break waves and bores) rather than full-duration tsunami waves, or have used simplified models of nearshore and over-land flows. Over the last 10+ years, pneumatic Tsunami Simulators for the hydraulic laboratory have been developed into an exciting and versatile technology, allowing the forces of real-world tsunami to be reproduced and measured in a laboratory environment for the first time. These devices have been used to model generic elevated and N-wave tsunamis up to and over simple shorelines, and at example coastal defences and infrastructure. They have also reproduced full-duration tsunamis including Mercator 2004 and Tohoku 2011, both at 1:50 scale. Engineering scale models of these tsunamis have measured wave run-up on simple slopes, forces on idealised sea defences, pressures / forces on buildings, and scour at idealised buildings. This presentation will describe how these Tsunami Simulators work, demonstrate how they have generated tsunami waves longer than the facilities within which they operate, and will present research results from three generations of Tsunami Simulators. Highlights of direct importance to natural hazard modellers and coastal engineers include measurements of wave run-up levels, forces on single and multiple buildings and comparison with previous theoretical predictions. Multiple buildings have two malign effects. The density of buildings to flow area (blockage ratio) increases water depths and flow velocities in the 'streets'. But the increased building densities themselves also increase the cost of flow per unit area (both personal and monetary). The most recent study with the Tsunami Simulators therefore focussed on the influence of multiple buildings (up to 4 rows) which showed (for instance) that the greatest forces can act on the landward (not seaward) rows of buildings. Studies in the 70m long, 4m wide main channel of the Fast Flow Facility on tsunami defence structures have also measured forces on buildings in the lee of a failed defence wall and tsunami induced scour. Supporting presentations at this conference: McGovern et al on tsunami induced scour at coastal structures and Foster et al on building loads.

Tsunami deposits associated with the 7.3 ka caldera-forming eruption of the Kikai Caldera, insights for tsunami generation during submarine caldera-forming eruptions

NASA Astrophysics Data System (ADS)

Geshi, Nobuo; Maeno, Fukashi; Nakagawa, Shojiro; Naruo, Hideto; Kobayashi, Tetsuo

2017-11-01

Timing and mechanism of volcanic tsunamis will be a key to understand the dynamics of large-scale submarine explosive volcanism. Tsunami deposits associated with the VEI 7 eruption of the Kikai Caldera at 7.3 ka are found in the Yakushima and Kuchinoerabujima Islands, 40 km south -southeast of the caldera rim. The tsunami deposits distribute along the rivers in their northern coast up to 4.5 km from the river exit and up to 50 m above the present sea level. The tsunami deposits in the Yakushima area consist of pumice-bearing gravels in the lower part of the section (Unit I) and pumiceous conglomerate in the upper part (Unit II). The presence of rounded pebbles of sedimentary rocks, which characterize the beach deposit, indicates a run-up current from the coastal area. The rip-up clasts of the underlying paleosol in Unit I show strong erosion during the invasion of tsunami. Compositional similarity between the pumices in the tsunami deposit and the juvenile materials erupted in the early phase of the Akahoya eruption indicates the formation of tsunami deposit during the early phase of the eruption, which produced the initial Plinian pumice fall and the lower half of the Koya pyroclastic flow. Presence of the dense volcanic components (obsidians and lava fragments) besides pumices in the tsunami deposit supports that they were carried by the Koya pyroclastic flow, and not the pumices floating on the sea surface. Sequential relationship between the Koya pyroclastic flow and the tsunami suggests that the emplacement of the pyroclastic flow into the sea surrounding the caldera is the most probable mechanism of the tsunami.

Shallow water models as tool for tsunami current predictions in ports and harbors. Validation with Tohoku 2011 field data

NASA Astrophysics Data System (ADS)

Gonzalez Vida, J. M., Sr.; Macias Sanchez, J.; Castro, M. J.; Ortega, S.

2015-12-01

Model ability to compute and predict tsunami flow velocities is of importance in risk assessment and hazard mitigation. Substantial damage can be produced by high velocity flows, particularly in harbors and bays, even when the wave height is small. Besides, an accurate simulation of tsunami flow velocities and accelerations is fundamental for advancing in the study of tsunami sediment transport. These considerations made the National Tsunami Hazard Mitigation Program (NTHMP) proposing a benchmark exercise focused on modeling and simulating tsunami currents. Until recently, few direct measurements of tsunami velocities were available to compare and to validate model results. After Tohoku 2011 many current meters measurement were made, mainly in harbors and channels. In this work we present a part of the contribution made by the EDANYA group from the University of Malaga to the NTHMP workshop organized at Portland (USA), 9-10 of February 2015. We have selected three out of the five proposed benchmark problems. Two of them consist in real observed data from the Tohoku 2011 event, one at Hilo Habour (Hawaii) and the other at Tauranga Bay (New Zealand). The third one consists in laboratory experimental data for the inundation of Seaside City in Oregon. For this model validation the Tsunami-HySEA model, developed by EDANYA group, was used. The overall conclusion that we could extract from this validation exercise was that the Tsunami-HySEA model performed well in all benchmark problems proposed. The greater spatial variability in tsunami velocity than wave height makes it more difficult its precise numerical representation. The larger variability in velocities is likely a result of the behaviour of the flow as it is channelized and as it flows around bathymetric highs and structures. In the other hand wave height do not respond as strongly to chanelized flow as current velocity.

Real-time tsunami inundation forecasting and damage mapping towards enhancing tsunami disaster resiliency

NASA Astrophysics Data System (ADS)

Koshimura, S.; Hino, R.; Ohta, Y.; Kobayashi, H.; Musa, A.; Murashima, Y.

2014-12-01

With use of modern computing power and advanced sensor networks, a project is underway to establish a new system of real-time tsunami inundation forecasting, damage estimation and mapping to enhance society's resilience in the aftermath of major tsunami disaster. The system consists of fusion of real-time crustal deformation monitoring/fault model estimation by Ohta et al. (2012), high-performance real-time tsunami propagation/inundation modeling with NEC's vector supercomputer SX-ACE, damage/loss estimation models (Koshimura et al., 2013), and geo-informatics. After a major (near field) earthquake is triggered, the first response of the system is to identify the tsunami source model by applying RAPiD Algorithm (Ohta et al., 2012) to observed RTK-GPS time series at GEONET sites in Japan. As performed in the data obtained during the 2011 Tohoku event, we assume less than 10 minutes as the acquisition time of the source model. Given the tsunami source, the system moves on to running tsunami propagation and inundation model which was optimized on the vector supercomputer SX-ACE to acquire the estimation of time series of tsunami at offshore/coastal tide gauges to determine tsunami travel and arrival time, extent of inundation zone, maximum flow depth distribution. The implemented tsunami numerical model is based on the non-linear shallow-water equations discretized by finite difference method. The merged bathymetry and topography grids are prepared with 10 m resolution to better estimate the tsunami inland penetration. Given the maximum flow depth distribution, the system performs GIS analysis to determine the numbers of exposed population and structures using census data, then estimates the numbers of potential death and damaged structures by applying tsunami fragility curve (Koshimura et al., 2013). Since the tsunami source model is determined, the model is supposed to complete the estimation within 10 minutes. The results are disseminated as mapping products to responders and stakeholders, e.g. national and regional municipalities, to be utilized for their emergency/response activities. In 2014, the system is verified through the case studies of 2011 Tohoku event and potential earthquake scenarios along Nankai Trough with regard to its capability and robustness.

Numerical experiment on tsunami deposit distribution process by using tsunami sediment transport model in historical tsunami event of megathrust Nankai trough earthquake

NASA Astrophysics Data System (ADS)

Imai, K.; Sugawara, D.; Takahashi, T.

2017-12-01

A large flow caused by tsunami transports sediments from beach and forms tsunami deposits in land and coastal lakes. A tsunami deposit has been found in their undisturbed on coastal lakes especially. Okamura & Matsuoka (2012) found some tsunami deposits in the field survey of coastal lakes facing to the Nankai trough, and tsunami deposits due to the past eight Nankai Trough megathrust earthquakes they identified. The environment in coastal lakes is stably calm and suitable for tsunami deposits preservation compared to other topographical conditions such as plains. Therefore, there is a possibility that the recurrence interval of megathrust earthquakes and tsunamis will be discussed with high resolution. In addition, it has been pointed out that small events that cannot be detected in plains could be separated finely (Sawai, 2012). Various aspects of past tsunami is expected to be elucidated, in consideration of topographical conditions of coastal lakes by using the relationship between the erosion-and-sedimentation process of the lake bottom and the external force of tsunami. In this research, numerical examination based on tsunami sediment transport model (Takahashi et al., 1999) was carried out on the site Ryujin-ike pond of Ohita, Japan where tsunami deposit was identified, and deposit migration analysis was conducted on the tsunami deposit distribution process of historical Nankai Trough earthquakes. Furthermore, examination of tsunami source conditions is possibly investigated by comparison studies of the observed data and the computation of tsunami deposit distribution. It is difficult to clarify details of tsunami source from indistinct information of paleogeographical conditions. However, this result shows that it can be used as a constraint condition of the tsunami source scale by combining tsunami deposit distribution in lakes with computation data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pudasaini, Shiva P.; Miller, Stephen A.

The general two-phase debris flow model proposed by Pudasaini is employed to study subaerial and submarine debris flows, and the tsunami generated by the debris impact at lakes and oceans. The model, which includes three fundamentally new and dominant physical aspects such as enhanced viscous stress, virtual mass, and generalized drag (in addition to buoyancy), constitutes the most generalized two-phase flow model to date. The advantage of this two-phase debris flow model over classical single-phase, or quasi-two-phase models, is that the initial mass can be divided into several parts by appropriately considering the solid volume fraction. These parts include amore » dry (landslide or rock slide), a fluid (water or muddy water; e.g., dams, rivers), and a general debris mixture material as needed in real flow simulations. This innovative formulation provides an opportunity, within a single framework, to simultaneously simulate the sliding debris (or landslide), the water lake or ocean, the debris impact at the lake or ocean, the tsunami generation and propagation, the mixing and separation between the solid and fluid phases, and the sediment transport and deposition process in the bathymetric surface. Applications of this model include (a) sediment transport on hill slopes, river streams, hydraulic channels (e.g., hydropower dams and plants); lakes, fjords, coastal lines, and aquatic ecology; and (b) submarine debris impact and the rupture of fiber optic, submarine cables and pipelines along the ocean floor, and damage to offshore drilling platforms. Numerical simulations reveal that the dynamics of debris impact induced tsunamis in mountain lakes or oceans are fundamentally different than the tsunami generated by pure rock avalanches and landslides. The analysis includes the generation, amplification and propagation of super tsunami waves and run-ups along coastlines, debris slide and deposition at the bottom floor, and debris shock waves. It is observed that the submarine debris speed can be faster than the tsunami speed. This information can be useful for early warning strategies in the coastal regions. These findings substantially increase our understanding of complex multi-phase systems and multi-physics and flows, and allows for the proper modeling of landslide and debris induced tsunami, the dynamics of turbidity currents and sediment transport, and the associated applications to hazard mitigation, geomorphology and sedimentology.« less

Pedestrian flow-path modeling to support tsunami-evacuation planning

NASA Astrophysics Data System (ADS)

Wood, N. J.; Jones, J. M.; Schmidtlein, M.

2015-12-01

Near-field tsunami hazards are credible threats to many coastal communities throughout the world. Along the U.S. Pacific Northwest coast, low-lying areas could be inundated by a series of catastrophic tsunamis potentially arriving in a matter of minutes following a Cascadia subduction zone (CSZ) earthquake. We developed a geospatial-modeling method for characterizing pedestrian-evacuation flow paths and evacuation basins to support evacuation and relief planning efforts for coastal communities in this region. We demonstrate this approach using the coastal communities of Aberdeen, Hoquiam, and Cosmopolis in southwestern Grays Harbor County, Washington (USA), where previous research suggests approximately 20,500 people (99% of the residents in tsunami-hazard zones) will likely have enough time to evacuate before tsunami-wave arrival. Geospatial, anisotropic, path distance models were developed to map the most efficient pedestrian paths to higher ground from locations within the tsunami-hazard zone. This information was then used to identify evacuation basins, outlining neighborhoods sharing a common evacuation pathway to safety. We then estimated the number of people traveling along designated evacuation pathways and arriving at pre-determined safe assembly areas, helping determine shelter demand and relief support (e.g., for elderly individuals or tourists). Finally, we assessed which paths may become inaccessible due to earthquake-induced ground failures, a factor which may impact an individual's success in reaching safe ground. The presentation will include a discussion of the implications of our analysis for developing more comprehensive coastal community tsunami-evacuation planning strategies worldwide.

Field Observations Of The 29 September Tsunami In American Samoa: Spatial Variability And Indications Of Strong Return Flow

NASA Astrophysics Data System (ADS)

Jaffe, B. E.; Richmond, B. M.; Gelfenbaum, G. R.; Watt, S.; Apotsos, A. A.; Buckley, M. L.; Dudley, W. C.; Peck, B.

2009-12-01

The 29 September 2009 tsunami caused 181 fatalities and displaced more than 5000 people on the islands of Samoa, American Samoa, and Tonga. This is the first tsunami to cause significant damage and fatalities on U.S. soil in more than 30 years. Scientists from around the world quickly mobilized to help document the tsunami water levels before this ephemeral data was forever lost as recovery activities and natural processes overtook the effected area. A USGS team collected data in American Samoa from October 6-22 and November 5-12, 2009. The tsunami was large, reaching elevations of greater than 15 m, however wave heights and devastation varied from village to village in American Samoa. Even within villages, some structures were completely destroyed, some flooded and left standing, and others barely touched. Wave heights, flow depths, runup heights, inundation distances, and flow directions were collected for use in ground-truthing inundation models. The team also collected nearshore bathymetry, topography and reef flat elevation, sediment samples, and documented the distribution and characteristics of both sand and boulder deposits. Eyewitness accounts of the tsunami were also videotaped. One striking aspect of this tsunami was the abundance of indicators of strong return flow. For example at Poloa in the northwest of Tutuila, where the runup was greater than 11 m along a 300-m stretch of coast and flow depths exceeded 4 m, the coral reef flat was strewn with debris including chairs, desks, and books from a school. On land, River channels were excavated and new channels formed as return flow scoured sediment and transported it offshore. Possible causes for the strong return flow and the relation between the stength of the return flow, inundation distance, and runup in American Samoa are presented. These relationships and others based on data collected by field survey teams will ultimately reduce loss of life and destruction from tsunamis in the Pacific and elsewhere.

How can coastal parks contain the destructive impact of a tsunami? A numerical approach to the understanding of tsunami-triggered waves in the presence of coastal hills

NASA Astrophysics Data System (ADS)

Marras, Simone; Suckale, Jenny; Lunghino, Brent; Giraldo, Francis X.; Constantinescu, Emil

2016-04-01

From the now common idea that vegetated shores may reduce the power of a destructive storm surge, an increasing number of coastal communities around the world are extending this thinking to the design of coastal parks as a way to limit the impact of a tsunami. Tsunamis and storm surges are significantly different in nature and behavior, and it is implausible that vegetation alone could act as a tsunami mitigation tool. A more comprehensive approach relies on the installation of vegetated, scattered mitigation hills in front of the shore to deviate the incoming tsunami wave instead. The analysis of how natural obstacles affect non-linear tsunami waves is still very limited and consists mostly of one-dimensional studies (e.g., [1, 2]). To that end, this work aims to extend the analysis of the interaction of waves of different shapes (solitary wave, N-wave), sizes (amplitude and wave length), and configurations with large obstacles to two-dimensional flows. The following metrics are used for a quantification of the results: 1) tsunami run-up and run-down and 2) a measure of channelization (via the flow kinetic energy and discharge). First, preliminary results show that the configuration of the obstacles is consequential as long as the amplitude of the incoming wave is large enough relative to the obstacles. In second instance, we also observed that the channelization of the flow between two neighboring obstacles may not be greatly affected solely by the distance between obstacles, but must be analyzed in relationship to the initial wave/wave train. This study is based on the numerical solution of the viscous shallow water equations via high order discontinuous finite elements method (DG) using a quadrilateral version of the model described in [3] and with fully implicit time integration [4]. Large and relatively massive hills appear to be a better solution than any offshore concrete walls, which have shown to possibly enhance the tsunami catastrophic power rather than reducing it. Nevertheless, without a thorough understanding of the behavior of non-linear waves when they approach coastal configurations such as hills, coastal parks may still be far from a safe reality. References [1] P. Lynett (2007) "Effect of shallow water obstruction on long wave run-up and overland flow velocity" J. Waterway, Port, Coastal, Ocean Engrg. 136:455-462 [2] G. F. Carrier, T. T. Wu, H. Yeh (2003) "Tsunami run-up and draw-down on a plane beach" J. Fluid Mech. 475:79-99. [3] F. X. Giraldo and M. Restelli (2010) "High-order semi- implicit time-integrators for a triangular discontinuous Galerkin oceanic shallow water model" Int. J. Numer. Methods Fluids, 63:1077-1102. [4] F X. Giraldo, J F.. Kelly, and E. Constantinescu. "Implicit-explicit formulations of a three-dimensional Nonhydrostatic Unified Model of the Atmosphere (NUMA)" SIAM J. Sci. Comput., 35:1162-1194, 2013.

Geomorphic impacts of the 2011 tsunami on the lower reaches of the R. Natori, northeast Japan

NASA Astrophysics Data System (ADS)

Shimazu, H.

2012-04-01

The tsunami caused by "the 2011 off the Pacific coast of Tohoku Earthquake" attacked Japan's east coast and inundated a large extent of the lowlands. The strong flood flow went upstream in the lower reaches of the rivers. The lower reaches of the rivers in Japan usually have unprotected dry riverbeds separated by dykes from floodplains where people live. The tsunami went upstream not only in the channels but also in the dry riverbeds. There is 1 kilometers wide unprotected dry riverbed in the lower reaches of the R. Natori, northeast Japan and they were used for vegetable farmlands. This study aims to discuss the geomorphic impacts of the tsunami on the dry riverbed in the lower reaches of the R. Natori. Surface sediments, micro-landforms and damages to agricultural facilities such as small poly tunnels, plastic mulches and support posts were examined to reconstruct the geomorphic impacts. Fieldworks were carried out at the beginning of May, 50 days after the tsunami disaster, and the end of August. Height of the tsunami near the river mouth was estimated over 3 meters. The flood flow went upstream to the sites at an elevation of 4 meters, 9 kilometers from the river mouth in the channel and 6.5 kilometers in the dry riverbed. Because the tsunami deposits are light colored sand and silt containing salinity, they could be distinguished from brown cultivated soil easily. The geomorphic impacts on the dry riverbed changed longitudinally. In the lowest 2.5 kilometers reaches strong flood flow and ebb flow caused strong erosion. It accounted for thin tsunami deposits with seashells and beach gravels, eroded scar, and dunes of downstream direction in the dry riverbed. In the next 1.5 kilometers reaches agricultural facilities were washed away or fell over upstream direction. Although the flood flow was still devastating, strength of the ebb flow gradually weakened. In this reaches dominant sedimentation process caused the tsunami deposits over 10 centimeters thick. In the reaches at about 5 kilometers from the river mouth, weakened and shallow tsunami flow went upstream through the relatively lower part. in the dry riverbed. Islands surrounded former channel courses were not damaged by the tsunami and vegetables in them grew as usual. The tsunami flooding at 6.5 kilometers from the river mouth inundated the dry riverbed and only thin deposits were left on it.

Power and Scour: Laboratory simulations of tsunami-induced scour

NASA Astrophysics Data System (ADS)

Todd, David; McGovern, David; Whitehouse, Richard; Harris, John; Rossetto, Tiziana

2017-04-01

The world's coastal regions are becoming increasingly urbanised and densely populated. Recent major tsunami events in regions such as Samoa (2007), Indonesia (2004, 2006, 2010), and Japan (2011) have starkly highlighted this effect, resulting in catastrophic loss of both life and property, with much of the damage to buildings being reported in EEFIT mission reports following each of these events. The URBANWAVES project, led by UCL in collaboration with HR Wallingford, brings the power of the tsunami to the laboratory for the first time. The Pneumatic Tsunami Simulator is capable of tsimulating both idealised and real-world tsunami traces at a scale of 1:50. Experiments undertaken in the Fast Flow Facility at HR Wallingford using square and rectangular buildings placed on a sediment bed have allow us to measure, for the first time under laboratory conditions, the variations in the flow field around buildings produced by tsunami waves as a result of the scour process. The results of these tests are presented, providing insight into the process of scour development under different types of tsunami, giving a glimpse into the power of tsunamis that have already occurred, and helping us to inform the designs of future buildings so that we can be better prepared to analyse and design against these failure modes in the future. Additional supporting abstracts include Foster et al., on tsunami induced building loads; Chandler et al., on the tsunami simulation concept and McGovern et al., on the simulation of tsunami-driven scour and flow fields.

Estimated damage from the Cascadia Subduction Zone tsunami: A model comparisons using fragility curves

NASA Astrophysics Data System (ADS)

Wiebe, D. M.; Cox, D. T.; Chen, Y.; Weber, B. A.; Chen, Y.

2012-12-01

Building damage from a hypothetical Cascadia Subduction Zone tsunami was estimated using two methods and applied at the community scale. The first method applies proposed guidelines for a new ASCE 7 standard to calculate the flow depth, flow velocity, and momentum flux from a known runup limit and estimate of the total tsunami energy at the shoreline. This procedure is based on a potential energy budget, uses the energy grade line, and accounts for frictional losses. The second method utilized numerical model results from previous studies to determine maximum flow depth, velocity, and momentum flux throughout the inundation zone. The towns of Seaside and Canon Beach, Oregon, were selected for analysis due to the availability of existing data from previously published works. Fragility curves, based on the hydrodynamic features of the tsunami flow (inundation depth, flow velocity, and momentum flux) and proposed design standards from ASCE 7 were used to estimate the probability of damage to structures located within the inundations zone. The analysis proceeded at the parcel level, using tax-lot data to identify construction type (wood, steel, and reinforced-concrete) and age, which was used as a performance measure when applying the fragility curves and design standards. The overall probability of damage to civil buildings was integrated for comparison between the two methods, and also analyzed spatially for damage patterns, which could be controlled by local bathymetric features. The two methods were compared to assess the sensitivity of the results to the uncertainty in the input hydrodynamic conditions and fragility curves, and the potential advantages of each method discussed. On-going work includes coupling the results of building damage and vulnerability to an economic input output model. This model assesses trade between business sectors located inside and outside the induction zone, and is used to measure the impact to the regional economy. Results highlight critical businesses sectors and infrastructure critical to the economic recovery effort, which could be retrofitted or relocated to survive the event. The results of this study improve community understanding of the tsunami hazard for civil buildings.

Tsunami: ocean dynamo generator.

PubMed

Sugioka, Hiroko; Hamano, Yozo; Baba, Kiyoshi; Kasaya, Takafumi; Tada, Noriko; Suetsugu, Daisuke

2014-01-08

Secondary magnetic fields are induced by the flow of electrically conducting seawater through the Earth's primary magnetic field ('ocean dynamo effect'), and hence it has long been speculated that tsunami flows should produce measurable magnetic field perturbations, although the signal-to-noise ratio would be small because of the influence of the solar magnetic fields. Here, we report on the detection of deep-seafloor electromagnetic perturbations of 10-micron-order induced by a tsunami, which propagated through a seafloor electromagnetometer array network. The observed data extracted tsunami characteristics, including the direction and velocity of propagation as well as sea-level change, first to verify the induction theory. Presently, offshore observation systems for the early forecasting of tsunami are based on the sea-level measurement by seafloor pressure gauges. In terms of tsunami forecasting accuracy, the integration of vectored electromagnetic measurements into existing scalar observation systems would represent a substantial improvement in the performance of tsunami early-warning systems.

Hydrodynamic modeling of tsunamis from the Currituck landslide

USGS Publications Warehouse

Geist, E.L.; Lynett, P.J.; Chaytor, J.D.

2009-01-01

Tsunami generation from the Currituck landslide offshore North Carolina and propagation of waves toward the U.S. coastline are modeled based on recent geotechnical analysis of slide movement. A long and intermediate wave modeling package (COULWAVE) based on the non-linear Boussinesq equations are used to simulate the tsunami. This model includes procedures to incorporate bottom friction, wave breaking, and overland flow during runup. Potential tsunamis generated from the Currituck landslide are analyzed using four approaches: (1) tsunami wave history is calculated from several different scenarios indicated by geotechnical stability and mobility analyses; (2) a sensitivity analysis is conducted to determine the effects of both landslide failure duration during generation and bottom friction along the continental shelf during propagation; (3) wave history is calculated over a regional area to determine the propagation of energy oblique to the slide axis; and (4) a high-resolution 1D model is developed to accurately model wave breaking and the combined influence of nonlinearity and dispersion during nearshore propagation and runup. The primary source parameter that affects tsunami severity for this case study is landslide volume, with failure duration having a secondary influence. Bottom friction during propagation across the continental shelf has a strong influence on the attenuation of the tsunami during propagation. The high-resolution 1D model also indicates that the tsunami undergoes nonlinear fission prior to wave breaking, generating independent, short-period waves. Wave breaking occurs approximately 40-50??km offshore where a tsunami bore is formed that persists during runup. These analyses illustrate the complex nature of landslide tsunamis, necessitating the use of detailed landslide stability/mobility models and higher-order hydrodynamic models to determine their hazard.

Errors in Tsunami Source Estimation from Tide Gauges

NASA Astrophysics Data System (ADS)

Arcas, D.

2012-12-01

Linearity of tsunami waves in deep water can be assessed as a comparison of flow speed, u to wave propagation speed √gh. In real tsunami scenarios this evaluation becomes impractical due to the absence of observational data of tsunami flow velocities in shallow water. Consequently the extent of validity of the linear regime in the ocean is unclear. Linearity is the fundamental assumption behind tsunami source inversion processes based on linear combinations of unit propagation runs from a deep water propagation database (Gica et al., 2008). The primary tsunami elevation data for such inversion is usually provided by National Oceanic and Atmospheric (NOAA) deep-water tsunami detection systems known as DART. The use of tide gauge data for such inversions is more controversial due to the uncertainty of wave linearity at the depth of the tide gauge site. This study demonstrates the inaccuracies incurred in source estimation using tide gauge data in conjunction with a linear combination procedure for tsunami source estimation.

Diatom assemblages as guides to flow conditions during the 2004 Indian Ocean tsunami at Phra Thong Island, Thailand

NASA Astrophysics Data System (ADS)

Sawai, Y.; Jankaew, K.; Martin, M. E.; Choowong, M.; Charoentitirat, T.; Prendergast, A.

2008-12-01

Diatom assemblages in the 2004 tsunami deposits of Phra Thong Island, Thailand represent flow conditions during the tsunami. The tsunami deposit consists of single or multiple graded beds. Diatom assemblages in the lowermost part of the deposit predominantly comprise beach and subtidal species. In the middle part of the deposit, the assemblages are dominated by marine plankton with increasing finer fractions. A mixed assemblage of freshwater, brackish, and marine species occupies the uppermost part of the deposit. Changes in flow conditions during the tsunami can explain these diatom assemblage variations. During fast current velocities, medium sand is deposited; only beach and subtidal diatoms that live attached to the sand can be incorporated into the tsunami deposit under these flow conditions. It is difficult for diatoms in suspension to settle out under fast current velocities. With decreasing current velocities, marine plankton can settle out of the water column .Finally, during the suspension stage (calm currents) between tsunami waves, the entrained freshwater, brackish, and marine species settle out with mud and plant trash. Fewer broken valves in the lowermost part of the deposit is probably a results of rapid entrainment, whilst selective breakage of marine plankton (Thalassionema nitzschioides, and Thalassiosira and Coscinodiscus spp.) in the middle part of the deposit probably results from abrasion by turbulent current before their deposition.

Recent Advances in Tsunami-Seabed-Structure Interaction from Geotechnical and Hydrodynamic Perspectives

NASA Astrophysics Data System (ADS)

Sassa, S.

2017-12-01

This presentation shows some recent research advances on tsunami-seabed-structure interaction following the 2011 Tohoku Earthquake Tsunami, Japan. It presents a concise summary and discussion of utilizing a geotechnical centrifuge and a large-scale hydro flume for the modelling of tsunami-seabed-structure interaction. I highlight here the role of tsunami-induced seepage in piping/boiling, erosion and bearing capacity decrease and failure of the rubble/seabed foundation. A comparison and discussion are made on the stability assessment for the design of tsunami-resistant structures on the basis of the results from both geo-centrifuge and large-scale hydrodynamic experiments. The concurrent processes of the instability involving the scour of the mound/sandy seabed, bearing capacity failure and flow of the foundation and the failure of caisson breakwaters under tsunami overflow and seepage coupling are made clear in this presentation. Three series of experiments were conducted under fifty gravities. The first series of experiments targeted the instability of the mounds themselves, and the second series of experiments clarified how the mound scour would affect the overall stability of the caissons. The third series of experiments examined the effect of a countermeasure on the basis of the results from the two series of experiments. The experimental results first demonstrated that the coupled overflow-seepage actions promoted the development of the mound scour significantly, and caused bearing capacity failure of the mound, resulting in the total failure of the caisson breakwater, which otherwise remained stable without the coupling effect. The velocity vectors obtained from the high-resolution image analysis illustrated the series of such concurrent scour/bearing-capacity-failure/flow processes leading to the instability of the breakwater. The stability of the breakwaters was significantly improved with decreasing hydraulic gradient underneath the caissons due to an embankment effect. These findings elucidate the crucial role of overflow/seepage coupling in tsunami-seabed-structure interaction from both geotechnical and hydrodynamic perspectives, as an interdisciplinary tsunami science, warranting an enhanced disaster resilience.

Severity and exposure associated to tsunami actions in urban waterfronts. The case of Lisbon, Portugal.

NASA Astrophysics Data System (ADS)

Conde, Daniel; Telhado, Maria J.; Viana Baptista, Maria A.; Antunes, Carlos M.; Ferreira, Rui M. L.

2014-05-01

The Tagus estuary is recognized as an exposed location to tsunami occurrences, given its proximity to tsunamigenic faults such as the Marquês de Pombal and the Horseshoe fault system. Lisbon, bordered by the Tagus estuary, is a critical point of Portugal's tsunami hazard map, having been affected by several tsunamis (Baptista and Miranda, 2009) including the notorious event of November 1st 1755, the last major natural disaster known to have inflicted massive destruction in Portugal. The main objective of this work, a joint initiative of CEHIDRO (IST - Universidade de Lisboa) and the Municipal Civil Protection Services of Lisbon, is to contribute to the quantification of severity and exposure of Lisbon waterfront to tsunami events. For that purpose, the propagation of a tsunami similar to that of the 1st November of 1755 in the Tagus estuary was numerically simulated. Several scenarios were considered, articulating the influence of tidal (low and high tides), atmospheric (increase in water level due to storm surges) and hydrological (flow discharge in Tagus river) conditions. Different initial and boundary conditions were defined for each modelling scenario but the magnitude of the tsunami remained what is believed to be an exceptional event. The extent of the inundation and relevant hydrodynamic quantities were registered for all scenarios. The employed simulation tool - STAV-2D - was developed at CEHIDRO (IST) and is based on a 2DH spatial (Eulerian) shallow-flow approach suited to complex and dynamic bottom boundaries. The discretization technique relies on a finite-volume scheme, based on a flux-splitting technique incorporating a reviewed version of the Roe Riemann solver (Canelas et al. 2013, Conde et al. 2013). STAV-2D features conservation equations for the finer solid phase of the flow and also a Lagrangian model for the advection of larger debris elements. The urban meshwork was thoroughly discretized with a mesh finer than average street width. This fine discretization allows for resolving flow resistance associated to obstacles: no ad hoc formulations are needed to express drag on buildings, which is a key innovation in regard to previous studies. Additionally, vehicle-like particles were virtually placed over the major traffic nodes and routes, resulting in over 5000 lagrangian particles along the riverfront. This allows for an assessment of debris deposition patterns on the aftermath of the tsunami inundation. Severity is herein assumed to depend on hydrodynamic features of the tsunami, namely its capacity to impart momentum. Exposure to tsunami actions depends on the extent of the inundation. Both severity and exposure thus vary with the tsunami scenario considered. The obtained results, obtained with a high detail of hydrodynamic behavior, allow for a street-by-street quantification of severity, expressed in terms of the product of the depth-averaged velocity by the flow depth (Karvonen et al., 2000), herein the q-parameter. This parameter is shown to be larger during run-up, particularly in streets and narrow sections. It was observed that the scenario with greater exposure is a combination of a high-tide, a storm surge and a discharge equivalent to a 100 year flood on the Tagus River. The work conducted allows for designing a methodology for exposure assessment due to tsunami propagating over urban meshes, where the influence of the existing infrastructures on the incoming inundation is highly relevant. Such methodology, here applied to Lisbon waterfront, is general since it is defined in terms of quantifiable hydrodynamic variables. Acknowledgements: Project RECI/ECM-HID/0371/2012, funded by the Portuguese Foundation for Science and Technology (FCT), has partially supported this work. References: Baptista, M.A., Miranda, J.M. (2009). Revision of the Portuguese catalog of tsunamis. Nat. Hazards Earth Syst. Sci., 9, 25 - 42. Canelas, R., Murillo, J. & Ferreira, R.M.L. (2013). Two-dimensional depth-averaged modelling of dam-break flows over mobile beds. Journal of Hydraulic Research, 51(4), 392-407. Conde, D., Baptista, M. A. V., Sousa Oliveira, C., and Ferreira, R. M. L. (2013). A shallow-flow model for the propagation of tsunamis over complex geometries and mobile beds, Nat. Hazards Earth Syst. Sci., 13, 2533-2542. Karvonen, R.A., Hepojoki, A., Huhta, H.K., and Louhio, A. (2000) The Use of Physical Models in Dam-Break Analysis. RESCDAM Final Report. Helsinki University of Technology, Helsinki, Finland.

Laboratory Experiments of Tsunami Inundation in Patchy Coastal Forest on a Steep Beach

NASA Astrophysics Data System (ADS)

Irish, J. L.; Weiss, R.; Yang, Y.; Zainali, A.; Marivela Colmenarejo, R.

2014-12-01

Tsunamis are a leading natural threat to coastal communities, and events such as the 2011 Japan and 2004 Indian Ocean tsunamis caused widespread, crippling damages to coastal infrastructure. Yet, these events also called attention to the role of coastal forest as sustainable mitigation against tsunami hazard. Here, we present large-scale experiments of tsunami runup and withdrawal on a steeply sloping beach in the presence of patchy forest. The forest is modeled using 1.2-m diameter macro-roughness patches of varying resistance were constructed from staggered arrays of 2.7-cm diameter rigid cylinders. Macro-roughness patches were affixed in a staggered arrangement with mean spacing of 3.2 m between patches (Fig. 1). The basin depth and wave height at the wavemaker were 0.73 m and 0.43 m, respectively, such that a broken roller formed offshore of the still-water line. Point measurements of velocity and flow depth were made at twenty locations using co-located acoustic Doppler velocimeters and sonic wave gauges, respectively, in order to construct a flow field in the vicinity of three macro-roughness patches. Simultaneous, high-resolution video was also collected in order to track the runup bore position in time. Analysis of mean flow conditions reveals that patchy roughness induces non-uniform changes in momentum flux throughout the patch array (Fig. 2). During runup, momentum flux is generally reduced in the lee of the patches. However, flow channelization between cross-shore rows of patches leads to an increase in momentum flux. During withdrawal, the strong gravity-driven flows that develop as a result of the steep 1:10 beach lead to an increase in momentum flux in areas behind the patches, which benefited from reduced momentum flux during runup. The experiment findings indicate that flow interactions with the natural environment are indeed complex and that care must be exercised when considering the use of coastal forest as a tsunami bioshield. Acknowledgements: This material is based upon work supported by the National Science Foundation under Grant Number CMMI-1206271. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

A Preliminary Tsunami vulnerability analysis for Bakirkoy district in Istanbul

NASA Astrophysics Data System (ADS)

Tufekci, Duygu; Lutfi Suzen, M.; Cevdet Yalciner, Ahmet; Zaytsev, Andrey

2016-04-01

Resilience of coastal utilities after earthquakes and tsunamis has major importance for efficient and proper rescue and recovery operations soon after the disasters. Vulnerability assessment of coastal areas under extreme events has major importance for preparedness and development of mitigation strategies. The Sea of Marmara has experienced numerous earthquakes as well as associated tsunamis. There are variety of coastal facilities such as ports, small craft harbors, and terminals for maritime transportation, water front roads and business centers mainly at North Coast of Marmara Sea in megacity Istanbul. A detailed vulnerability analysis for Yenikapi region and a detailed resilience analysis for Haydarpasa port in Istanbul have been studied in previously by Cankaya et al., (2015) and Aytore et al., (2015) in SATREPS project. In this study, the methodology of vulnerability analysis under tsunami attack given in Cankaya et al., (2015) is modified and applied to Bakirkoy district of Istanbul. Bakirkoy district is located at western part of Istanbul and faces to the North Coast of Marmara Sea from 28.77oE to 28.89oE. High resolution spatial dataset of Istanbul Metropolitan Municipality (IMM) is used and analyzed. The bathymetry and topography database and the spatial dataset containing all buildings/structures/infrastructures in the district are collated and utilized for tsunami numerical modeling and following vulnerability analysis. The tsunami parameters from deterministically defined worst case scenarios are computed from the simulations using tsunami numerical model NAMI DANCE. The vulnerability assessment parameters in the district according to vulnerability and resilience are defined; and scored by implementation of a GIS based TVA with appropriate MCDA methods. The risk level is computed using tsunami intensity (level of flow depth from simulations) and TVA results at every location in Bakirkoy district. The preliminary results are presented and discussed. Acknowledgements: Partial support by Japan-Turkey Joint Research Project by JICA on earthquakes and tsunamis in Marmara Region in (JICA SATREPS - MarDiM Project), 603839 ASTARTE Project of EU, UDAP-C-12-14 project of AFAD, Turkey, 108Y227, 113M556, 213M534 projects of TUBITAK Turkey, RAPSODI (CONCERT_Dis-021) of CONCERT-Japan Joint Call and Istanbul Metropolitan Municipality are acknowledged.

Source mechanisms of volcanic tsunamis.

PubMed

Paris, Raphaël

2015-10-28

Volcanic tsunamis are generated by a variety of mechanisms, including volcano-tectonic earthquakes, slope instabilities, pyroclastic flows, underwater explosions, shock waves and caldera collapse. In this review, we focus on the lessons that can be learnt from past events and address the influence of parameters such as volume flux of mass flows, explosion energy or duration of caldera collapse on tsunami generation. The diversity of waves in terms of amplitude, period, form, dispersion, etc. poses difficulties for integration and harmonization of sources to be used for numerical models and probabilistic tsunami hazard maps. In many cases, monitoring and warning of volcanic tsunamis remain challenging (further technical and scientific developments being necessary) and must be coupled with policies of population preparedness. © 2015 The Author(s).

Fusion of real-time simulation, sensing, and geo-informatics in assessing tsunami impact

NASA Astrophysics Data System (ADS)

Koshimura, S.; Inoue, T.; Hino, R.; Ohta, Y.; Kobayashi, H.; Musa, A.; Murashima, Y.; Gokon, H.

2015-12-01

Bringing together state-of-the-art high-performance computing, remote sensing and spatial information sciences, we establish a method of real-time tsunami inundation forecasting, damage estimation and mapping to enhance disaster response. Right after a major (near field) earthquake is triggered, we perform a real-time tsunami inundation forecasting with use of high-performance computing platform (Koshimura et al., 2014). Using Tohoku University's vector supercomputer, we accomplished "10-10-10 challenge", to complete tsunami source determination in 10 minutes, tsunami inundation modeling in 10 minutes with 10 m grid resolution. Given the maximum flow depth distribution, we perform quantitative estimation of exposed population using census data and mobile phone data, and the numbers of potential death and damaged structures by applying tsunami fragility curve. After the potential tsunami-affected areas are estimated, the analysis gets focused and moves on to the "detection" phase using remote sensing. Recent advances of remote sensing technologies expand capabilities of detecting spatial extent of tsunami affected area and structural damage. Especially, a semi-automated method to estimate building damage in tsunami affected areas is developed using pre- and post-event high-resolution SAR (Synthetic Aperture Radar) data. The method is verified through the case studies in the 2011 Tohoku and other potential tsunami scenarios, and the prototype system development is now underway in Kochi prefecture, one of at-risk coastal city against Nankai trough earthquake. In the trial operation, we verify the capability of the method as a new tsunami early warning and response system for stakeholders and responders.

Time-dependent onshore tsunami response

USGS Publications Warehouse

Apotsos, Alex; Gelfenbaum, Guy R.; Jaffe, Bruce E.

2012-01-01

While bulk measures of the onshore impact of a tsunami, including the maximum run-up elevation and inundation distance, are important for hazard planning, the temporal evolution of the onshore flow dynamics likely controls the extent of the onshore destruction and the erosion and deposition of sediment that occurs. However, the time-varying dynamics of actual tsunamis are even more difficult to measure in situ than the bulk parameters. Here, a numerical model based on the non-linear shallow water equations is used to examine the effects variations in the wave characteristics, bed slope, and bottom roughness have on the temporal evolution of the onshore flow. Model results indicate that the onshore flow dynamics vary significantly over the parameter space examined. For example, the flow dynamics over steep, smooth morphologies tend to be temporally symmetric, with similar magnitude velocities generated during the run-up and run-down phases of inundation. Conversely, on shallow, rough onshore topographies the flow dynamics tend to be temporally skewed toward the run-down phase of inundation, with the magnitude of the flow velocities during run-up and run-down being significantly different. Furthermore, for near-breaking tsunami waves inundating over steep topography, the flow velocity tends to accelerate almost instantaneously to a maximum and then decrease monotonically. Conversely, when very long waves inundate over shallow topography, the flow accelerates more slowly and can remain steady for a period of time before beginning to decelerate. These results indicate that a single set of assumptions concerning the onshore flow dynamics cannot be applied to all tsunamis, and site specific analyses may be required.

A Review of Methodologies on Vulnerability Assessment of Buildings to Tsunami Damage

NASA Astrophysics Data System (ADS)

Gunasekera, R.; Rosetto, T.; Tabuchi, S.; Suppasri, A.; Futami, T.; Scott, I.; Maegawa, H.

2012-04-01

The infrequency, suddenness and violence tsunamis has led to a lack of knowledge on tsunami and lack of data available for the calibration of numerical models particularly in relation to tsunami damage. Therefore, there are very few tsunami structural vulnerability studies available. Of the available literature, most of these started after the disastrous 2004 Indian Ocean event. Most of fragility curves have been developed in some areas struck by the 2004 tsunami, which are very different in architecture and engineering respect to the US, Japanese or European ones. This review aims to highlight the strengths and weaknesses of current knowledge on tsunami fragility by critically assessing several fragility curves based on post tsunami damage surveys in Chile, Japan (including initial findings of the March 2011 event), Samoa, Sri Lanka and Thailand. It is observed that there is no consensus on how to derive tsunami fragility curves. Most of the examined relationships are seen to relate to residential buildings, and, due to the location of recent tsunami occurrences, they mostly represent non-engineered buildings (i.e. all use data from Thailand, Sri Lanka, Samoa, or Sumatra), which limits their usefulness. In the absence of a good understanding of tsunami actions on buildings most existing fragility relationships adopt inundation depth as the hazard parameter in the vulnerability function, which does not account for the other components of onshore flow contributing to tsunami loads on buildings, such as flow velocity.

Tsunami Field Survey for the Solomon Islands Earthquake of April 1, 2007

NASA Astrophysics Data System (ADS)

Nishimura, Y.; Tanioka, Y.; Nakamura, Y.; Tsuji, Y.; Namegaya, Y.; Murata, M.; Woodward, S.

2007-12-01

Two weeks after the 2007 off-Solomon earthquake, an international tsunami survey team (ITST) of Japanese and US researchers performed a post tsunami survey in Ghizo and adjacent islands. Main purpose of the team was to provide information on the earthquake and tsunami to the national disaster council of the Solomon Islands, who was responsible for the disaster management at that time. The ITST had interview with the affected people and conducted reconnaissance mapping of the tsunami heights and flow directions. Tsunami flow heights at beach and inland were evaluated from watermarks on buildings and the position of broken branches and stuck materials on trees. These tsunami heights along the southern to western coasts of Ghizo Island were ca. 5m (a.s.l.). Tsunami run-up was traced by distribution of floating debris that carried up by the tsunami and deposited at their inundation limit. The maximum run-up was measured at Tapurai of Simbo Island to be ca. 9 m. Most of the inundation area was covered by 0-10 cm thick tsunami deposit that consists of beach sand, coral peaces and eroded soil. Coseismic uplift and subsidence were clearly identified by changes of the sea level before and after the earthquake, that were inferred by eyewitness accounts and evidences such as dried up coral reeves. These deformation patterns, as well as the tsunami height distribution, could constrain the earthquake fault geometry and motion. It is worthy of mention that the tsunami damage in villages in Ranongga Island has significantly reduced by 2-3 m uplift before the tsunami attack.

A consistent model for tsunami actions on buildings

NASA Astrophysics Data System (ADS)

Foster, A.; Rossetto, T.; Eames, I.; Chandler, I.; Allsop, W.

2016-12-01

The Japan (2011) and Indian Ocean (2004) tsunami resulted in significant loss of life, buildings, and critical infrastructure. The tsunami forces imposed upon structures in coastal regions are initially due to wave slamming, after which the quasi-steady flow of the sea water around buildings becomes important. An essential requirement in both design and loss assessment is a consistent model that can accurately predict these forces. A model suitable for predicting forces in the in the quasi-steady range has been established as part of a systematic programme of research by the UCL EPICentre to understand the fundamental physical processes of tsunami actions on buildings, and more generally their social and economic consequences. Using the pioneering tsunami generator at HR Wallingford, this study considers the influence of unsteady flow conditions on the forces acting upon a rectangular building occupying 10-80% of a channel for 20-240 second wave periods. A mathematical model based upon basic open-channel flow principles is proposed, which provides empirical estimates for drag and hydrostatic coefficients. A simple force prediction equation, requiring only basic flow velocity and wave height inputs is then developed, providing good agreement with the experimental results. The results of this study demonstrate that the unsteady forces from the very long waves encountered during tsunami events can be predicted with a level of accuracy and simplicity suitable for design and risk assessment.

Inter-model analysis of tsunami-induced coastal currents

NASA Astrophysics Data System (ADS)

Lynett, Patrick J.; Gately, Kara; Wilson, Rick; Montoya, Luis; Arcas, Diego; Aytore, Betul; Bai, Yefei; Bricker, Jeremy D.; Castro, Manuel J.; Cheung, Kwok Fai; David, C. Gabriel; Dogan, Gozde Guney; Escalante, Cipriano; González-Vida, José Manuel; Grilli, Stephan T.; Heitmann, Troy W.; Horrillo, Juan; Kânoğlu, Utku; Kian, Rozita; Kirby, James T.; Li, Wenwen; Macías, Jorge; Nicolsky, Dmitry J.; Ortega, Sergio; Pampell-Manis, Alyssa; Park, Yong Sung; Roeber, Volker; Sharghivand, Naeimeh; Shelby, Michael; Shi, Fengyan; Tehranirad, Babak; Tolkova, Elena; Thio, Hong Kie; Velioğlu, Deniz; Yalçıner, Ahmet Cevdet; Yamazaki, Yoshiki; Zaytsev, Andrey; Zhang, Y. J.

2017-06-01

To help produce accurate and consistent maritime hazard products, the National Tsunami Hazard Mitigation Program organized a benchmarking workshop to evaluate the numerical modeling of tsunami currents. Thirteen teams of international researchers, using a set of tsunami models currently utilized for hazard mitigation studies, presented results for a series of benchmarking problems; these results are summarized in this paper. Comparisons focus on physical situations where the currents are shear and separation driven, and are thus de-coupled from the incident tsunami waveform. In general, we find that models of increasing physical complexity provide better accuracy, and that low-order three-dimensional models are superior to high-order two-dimensional models. Inside separation zones and in areas strongly affected by eddies, the magnitude of both model-data errors and inter-model differences can be the same as the magnitude of the mean flow. Thus, we make arguments for the need of an ensemble modeling approach for areas affected by large-scale turbulent eddies, where deterministic simulation may be misleading. As a result of the analyses presented herein, we expect that tsunami modelers now have a better awareness of their ability to accurately capture the physics of tsunami currents, and therefore a better understanding of how to use these simulation tools for hazard assessment and mitigation efforts.

Geological effects and implications of the 2010 tsunami along the central coast of Chile

NASA Astrophysics Data System (ADS)

Morton, Robert A.; Gelfenbaum, Guy; Buckley, Mark L.; Richmond, Bruce M.

2011-12-01

Geological effects of the 2010 Chilean tsunami were quantified at five near-field sites along a 200 km segment of coast located between the two zones of predominant fault slip. Field measurements, including topography, flow depths, flow directions, scour depths, and deposit thicknesses, provide insights into the processes and morphological changes associated with tsunami inundation and return flow. The superposition of downed trees recorded multiple strong onshore and alongshore flows that arrived at different times and from different directions. The most likely explanation for the diverse directions and timing of coastal inundation combines (1) variable fault rupture and asymmetrical slip displacement of the seafloor away from the epicenter with (2) resonant amplification of coastal edge waves. Other possible contributing factors include local interaction of incoming flow and return flow and delayed wave reflection by the southern coast of Peru. Coastal embayments amplified the maximum inundation distances at two sites (2.4 and 2.6 km, respectively). Tsunami vertical erosion included scour and planation of the land surface, inundation scour around the bases of trees, and channel incision from return flow. Sheets and wedges of sand and gravel were deposited at all of the sites. Locally derived boulders up to 1 m in diameter were transported as much as 400 m inland and deposited as fields of dispersed clasts. The presence of lobate bedforms at one site indicates that at least some of the late-stage sediment transport was as bed load and not as suspended load. Most of the tsunami deposits were less than 25 cm thick. Exceptions were thick deposits near open-ocean river mouths where sediment supply was abundant. Human alterations of the land surface at most of the sites provided opportunities to examine some tsunami effects that otherwise would not have been possible, including flow histories, boulder dispersion, and vegetation controls on deposit thickness.

Geological effects and implications of the 2010 tsunami along the central coast of Chile

USGS Publications Warehouse

Morton, R.A.; Gelfenbaum, G.; Buckley, M.L.; Richmond, B.M.

2011-01-01

Geological effects of the 2010 Chilean tsunami were quantified at five near-field sites along a 200. km segment of coast located between the two zones of predominant fault slip. Field measurements, including topography, flow depths, flow directions, scour depths, and deposit thicknesses, provide insights into the processes and morphological changes associated with tsunami inundation and return flow. The superposition of downed trees recorded multiple strong onshore and alongshore flows that arrived at different times and from different directions. The most likely explanation for the diverse directions and timing of coastal inundation combines (1) variable fault rupture and asymmetrical slip displacement of the seafloor away from the epicenter with (2) resonant amplification of coastal edge waves. Other possible contributing factors include local interaction of incoming flow and return flow and delayed wave reflection by the southern coast of Peru. Coastal embayments amplified the maximum inundation distances at two sites (2.4 and 2.6. km, respectively). Tsunami vertical erosion included scour and planation of the land surface, inundation scour around the bases of trees, and channel incision from return flow. Sheets and wedges of sand and gravel were deposited at all of the sites. Locally derived boulders up to 1. m in diameter were transported as much as 400. m inland and deposited as fields of dispersed clasts. The presence of lobate bedforms at one site indicates that at least some of the late-stage sediment transport was as bed load and not as suspended load. Most of the tsunami deposits were less than 25. cm thick. Exceptions were thick deposits near open-ocean river mouths where sediment supply was abundant. Human alterations of the land surface at most of the sites provided opportunities to examine some tsunami effects that otherwise would not have been possible, including flow histories, boulder dispersion, and vegetation controls on deposit thickness. ?? 2011.

Geological impacts and implications of the 2010 tsunami along the central coast of Chile

USGS Publications Warehouse

Morton, Robert A.; Gelfenbaum, Guy; Buckley, Mark L.; Richmond, Bruce M.

2011-01-01

Geological effects of the 2010 Chilean tsunami were quantified at five near-field sites along a 200 km segment of coast located between the two zones of predominant fault slip. Field measurements, including topography, flow depths, flow directions, scour depths, and deposit thicknesses, provide insights into the processes and morphological changes associated with tsunami inundation and return flow. The superposition of downed trees recorded multiple strong onshore and alongshore flows that arrived at different times and from different directions. The most likely explanation for the diverse directions and timing of coastal inundation combines (1) variable fault rupture and asymmetrical slip displacement of the seafloor away from the epicenter with (2) resonant amplification of coastal edge waves. Other possible contributing factors include local interaction of incoming flow and return flow and delayed wave reflection by the southern coast of Peru. Coastal embayments amplified the maximum inundation distances at two sites (2.4 and 2.6 km, respectively). Tsunami vertical erosion included scour and planation of the land surface, inundation scour around the bases of trees, and channel incision from return flow. Sheets and wedges of sand and gravel were deposited at all of the sites. Locally derived boulders up to 1 m in diameter were transported as much as 400 m inland and deposited as fields of dispersed clasts. The presence of lobate bedforms at one site indicates that at least some of the late-stage sediment transport was as bed load and not as suspended load. Most of the tsunami deposits were less than 25 cm thick. Exceptions were thick deposits near open-ocean river mouths where sediment supply was abundant. Human alterations of the land surface at most of the sites provided opportunities to examine some tsunami effects that otherwise would not have been possible, including flow histories, boulder dispersion, and vegetation controls on deposit thickness.

Deposits, flow characteristics, and landscape change resulting from the September 2009 South Pacific tsunami in the Samoan islands

PubMed Central

Richmond, Bruce M.; Buckley, Mark; Etienne, Samuel; Chagué-Goff, Catherine; Clark, Kate; Goff, James; Dominey-Howes, Dale; Strotz, Luke

2011-01-01

The September 29th 2009 tsunami caused widespread coastal modification within the islands of Samoa and northern Tonga in the South Pacific. Preliminary measurements indicate maximum runup values of around 17 m (Okal et al., 2010) and shore-normal inundation distances of up to ~ 620 m (Jaffe et al., 2010). Geological field reconnaissance studies were conducted as part of an UNESCO-IOC International Tsunami Survey Team survey within three weeks of the event in order to document the erosion, transport, and deposition of sediment by the tsunami. Data collected included: a) general morphology and geological characteristics of the coast, b) evidence of tsunami flow (inundation, flow depth and direction, wave height and runup), c) surficial and subsurface sediment samples including deposit thickness and extent, d) topographic mapping, and e) boulder size and location measurements. Four main types of sedimentary deposits were identified: a) gravel fields consisting mostly of isolated cobbles and boulders, b) sand sheets from a few to ~ 25 cm thick, c) piles of organic (mostly vegetation) and man-made material forming debris ramparts, and d) surface mud deposits that settled from suspension from standing water in the tsunami aftermath. Tsunami deposits within the reef system were not widespread, however, surficial changes to the reefs were observed. PMID:27065478

Impacts of the 2004 Indian ocean tsunami on the southwest coasts of Sri Lanka

USGS Publications Warehouse

Morton, Robert A.; Goff, John A.; Nichol, Scott L.

2007-01-01

The 2004 Indian Ocean tsunami caused major landscape changes along the southwest coasts of Sri Lanka that were controlled by the flow, natural topography and bathymetry, and anthropogenic modifications of the terrain. Landscape changes included substantial beach erosion and scouring of return-flow channels near the beach, and deposition of sand sheets across the narrow coastal plain. In many areas tsunami deposits also included abundant building rubble due to the extensive destruction of homes and businesses in areas of dense development. Trim lines and flow directions confirmed that shoreline orientation and wave refraction from embayments and rock-anchored headlands locally focused the flow and amplified the inundation. Tsunami deposits were 1 to 36 cm thick but most were less than 25 cm thick. Deposit thickness depended partly on antecedent topography. The deposits were composed of coarse to medium sand organized into a few sets of plane parallel laminae that exhibited overall upward fining and landward thinning trends.

Pyroclastic Flow Generated Tsunami Waves Detected by CALIPSO Borehole Strainmeters at Soufriere Hills, Montserrat During Massive Dome Collapse: Numerical Simulations and Observations

NASA Astrophysics Data System (ADS)

van Boskirk, E. J.; Voight, B.; Watts, P.; Widiwijayanti, C.; Mattioli, G. S.; Elsworth, D.; Hidayat, D.; Linde, A.; Malin, P.; Neuberg, J.; Sacks, S.; Shalev, E.; Sparks, R. J.; Young, S. R.

2004-12-01

The July 12-13, 2003 eruption (dome collapse plus explosions) of Soufriere Hills Volcano in Montserrat, WI, is the largest historical lava dome collapse with ˜120 million cubic meters of the dome lost. Pyroclastic flows entered the sea at 18:00 AST 12 July at the Tar River Valley (TRV) and continued until the early hours of 13 July. Low-amplitude tsunamis were reported at Antigua and Guadaloupe soon after the dome collapse. At the time of eruption, four CALIPSO borehole-monitoring stations were in the process of being installed, and three very-broad-band Sacks-Evertson dilatometers were operational and recorded the event at 50 sps. The strongest strain signals were recorded at the Trants site, 5 km north of the TRV entry zone, suggesting tsunami waves >1 m high. Debris strandlines closer to TRV recorded runup heights as much as 8 m. We test the hypothesis that the strain signal is related to tsunami waves generated by successive pyroclastic flows induced during the dome collapse. Tsunami simulation models have been generated using GEOWAVE, which uses simple physics to recreate waves generated by idealized pyroclastic flows entering the sea at TRV. Each simulation run contains surface wave amplitude gauges located in key positions to the three borehole sites. These simulated wave amplitudes and periods are compared quantitatively with the data recorded by the dilatometers and with field observations of wave runup, to elucidate the dynamics of pyroclastic flow tsunami genesis and its propagation in shallow ocean water.

Tsunamis triggered by the 12 January 2010 Earthquake in Haiti

NASA Astrophysics Data System (ADS)

Fritz, H. M.; Hillaire, J. V.; Molière, E.; Mohammed, F.; Wei, Y.

2010-12-01

On 12 January 2010 a magnitude Mw 7.0 earthquake occurred 25 km west-southwest of Haiti’s Capital of Port-au-Prince, which resulted in more than 230,000 fatalities. In addition tsunami waves triggered by the earthquake caused at least 3 fatalities at Petit Paradis. Unfortunately, the people of Haiti had neither ancestral knowledge nor educational awareness of tsunami hazards despite the 1946 Dominican Republic tsunami at Hispaniola’s northeast coast. In sharp contrast Sri Lankan UN-soldiers on duty at Jacmel self-evacuated given the memory of the 2004 Indian Ocean tsunami. The International Tsunami Survey Team (ITST) documented flow depths, runup heights, inundation distances, sediment deposition, damage patterns at various scales, and performance of the man-made infrastructure and impact on the natural environment. The 31 January to 7 February 2010 ITST covered the greater Bay of Port-au-Prince and more than 100 km of Hispaniola’s south coast between Pedernales, Dominican Republic and Jacmel, Haiti. The Hispaniola survey data includes more than 20 runup and flow depth measurements. The tsunami impacts peaked with maximum flow depths exceeding 3 m both at Petit Paradis inside the Bay of Grand Goâve located 45 km west-southwest of Port-au-Prince and at Jacmel on Haiti’s south coast. A significant variation in tsunami impact was observed on Hispaniola and tsunami runup of more than 1 m was still observed at Pedernales in the Dominican Republic. Jacmel, which is near the center of the south coast, represents an unfortunate example of a village and harbor that was located for protection from storm waves but is vulnerable to tsunami waves with runup doubling from the entrance to the head of the bay. Inundation and damage was limited to less than 100 m inland at both Jacmel and Petit Paradis. Differences in wave period were documented between the tsunami waves at Petit Paradis and Jacmel. The Petit Paradis tsunami is attributed to a coastal submarine landslide. Field observations, video recordings, satellite imagery and numerical modelling are presented. The team interviewed numerous eyewitnesses and educated residents about the tsunami hazard. Community-based education and awareness programs are essential to save lives in locales at risk from locally generated tsunamis. Petit Paradis landslide scar with tree located 70m offshore

Assessment of tsunami resilience of Haydarpaşa Port in the Sea of Marmara by high-resolution numerical modeling

NASA Astrophysics Data System (ADS)

Aytore, Betul; Yalciner, Ahmet Cevdet; Zaytsev, Andrey; Cankaya, Zeynep Ceren; Suzen, Mehmet Lütfi

2016-08-01

Turkey is highly prone to earthquakes because of active fault zones in the region. The Marmara region located at the western extension of the North Anatolian Fault Zone (NAFZ) is one of the most tectonically active zones in Turkey. Numerous catastrophic events such as earthquakes or earthquake/landslide-induced tsunamis have occurred in the Marmara Sea basin. According to studies on the past tsunami records, the Marmara coasts have been hit by 35 different tsunami events in the last 2000 years. The recent occurrences of catastrophic tsunamis in the world's oceans have also raised awareness about tsunamis that might take place around the Marmara coasts. Similarly, comprehensive studies on tsunamis, such as preparation of tsunami databases, tsunami hazard analysis and assessments, risk evaluations for the potential tsunami-prone regions, and establishing warning systems have accelerated. However, a complete tsunami inundation analysis in high resolution will provide a better understanding of the effects of tsunamis on a specific critical structure located in the Marmara Sea. Ports are one of those critical structures that are susceptible to marine disasters. Resilience of ports and harbors against tsunamis are essential for proper, efficient, and successful rescue operations to reduce loss of life and property. Considering this, high-resolution simulations have been carried out in the Marmara Sea by focusing on Haydarpaşa Port of the megacity Istanbul. In the first stage of simulations, the most critical tsunami sources possibly effective for Haydarpaşa Port were inputted, and the computed tsunami parameters at the port were compared to determine the most critical tsunami scenario. In the second stage of simulations, the nested domains from 90 m gird size to 10 m grid size (in the port region) were used, and the most critical tsunami scenario was modeled. In the third stage of simulations, the topography of the port and its regions were used in the two nested domains in 3-m and 1-m resolutions and the water elevations computed from the previous simulations were inputted from the border of the large domain. A tsunami numerical code, NAMI DANCE, was used in the simulations. The tsunami parameters in the highest resolution were computed in and around the port. The effect of the data resolution on the computed results has been presented. The performance of the port structures and possible effects of tsunami on port operations have been discussed. Since the harbor protection structures have not been designed to withstand tsunamis, the breakwaters' stability becomes one of the major concerns for less agitation and inundation under tsunami in Haydarpaşa Port for resilience. The flow depth, momentum fluxes, and current pattern are the other concerns that cause unexpected circulations and uncontrolled movements of objects on land and vessels in the sea.

3D numerical investigation on landslide generated tsunamis around a conical island

NASA Astrophysics Data System (ADS)

Montagna, Francesca; Bellotti, Giorgio

2010-05-01

This paper presents numerical computations of tsunamis generated by subaerial and submerged landslides falling along the flank of a conical island. The study is inspired by the tsunamis that on 30th December 2002 attacked the coast of the volcanic island of Stromboli (South Tyrrhenian sea, Italy). In particular this paper analyzes the important feature of the lateral spreading of landside generated tsunamis and the associated flooding hazard. The numerical model used in this study is the full three dimensional commercial code FLOW-3D. The model has already been successfully used (Choi et al., 2007; 2008; Chopakatla et al, 2008) to study the interaction of waves and structures. In the simulations carried out in this work a particular feature of the code has been employed: the GMO (General Moving Object) algorithm. It allows to reproduce the interaction between moving objects, as a landslide, and the water. FLOW-3D has been firstly validated using available 3D experiments reproducing tsunamis generated by landslides at the flank of a conical island. The experiments have been carried out in the LIC laboratory of the Polytechnic of Bari, Italy (Di Risio et al., 2009). Numerical and experimental time series of run-up and sea level recorded at gauges located at the flanks of the island and offshore have been successfully compared. This analysis shows that the model can accurately represent the generation, the propagation and the inundation of landslide generated tsunamis and suggests the use of the numerical model as a tool for preparing inundation maps. At the conference we will present the validation of the model and parametric analyses aimed to investigate how wave properties depend on the landslide kinematic and on further parameters such as the landslide volume and shape, as well as the radius of the island. The expected final results of the research are precomputed inundation maps that depend on the characteristics of the landslide and of the island. Finally we will try to apply the code to a real life case i.e. the landslide tsunamis at the coast of the Stromboli island (Italy). SELECTED REFERENCES Choi, B.H. and D. C. Kim and E. Pelinovsky and S. B. Woo, 2007. Three dimensional simulation of tsunami run-up around conical island. Coastal Engineering 54,374 pp. 618-629. Chopakatla, S.C. and T.C. Lipmann and J.E. Richardson, 2008. Field verification of a computational fluid dynamics model for wave transformation and breaking in the surf zone. Journal of Waterway, Port, Coastal, and Ocean Engineering 134(2), pp. 71-80 Di Risio, M., P. De Girolamo, G. Bellotti, A. Panizzo, F. Aristodemo, M. G.Molfetta, and A. F. Petrillo (2009), Landslidegenerated tsunamis runup at the coast of a conical island: New physical model experiments. J. Geophys. Res., 114, C01009, doi:10.1029/2008JC004858 Flow Science, Inc, 2007. FLOW-3D User's Manual.

Erosion and sedimentation from the 17 July, 1998 Papua New Guinea tsunami

USGS Publications Warehouse

Gelfenbaum, G.; Jaffe, B.

2003-01-01

This paper describes erosion and sedimentation associated with the 17 July 1998 Papua New Guinea tsunami. Observed within two months of the tsunami, distinct deposits of a layer averaging 8-cm thick of gray sand rested on a brown muddy soil. In most cases the sand is normally graded, with more coarse sand near the base and fine sand at the top. In some cases the deposit contains rip-up clasts of muddy soil and in some locations it has a mud cap. Detailed measurements of coastal topography, tsunami flow height and direction indicators, and deposit thickness were made in the field, and samples of the deposit were collected for grain-size analysis in the laboratory. Four shore-normal transects were examined in detail to assess the shore-normal and along shore distribution of the tsunami deposit. Near the shoreline, the tsunami eroded approximately 10-25 cm of sand from the beach and berm. The sandy layer deposited by the tsunami began 50-150 m inland from the shoreline and extended across the coastal plain to within about 40 m of the limit of inundation; a total distance of up to 750 m from the beach. As much as 2/3 of the sand in the deposit originated from offshore. Across most of the coastal plain the deposit thickness and mean grain size varied little. In the along-shore direction the deposit thickness varied with the tsunami wave height; both largest near the entrance to Sissano Lagoon.

Development of a Probabilistic Tsunami Hazard Analysis in Japan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toshiaki Sakai; Tomoyoshi Takeda; Hiroshi Soraoka

2006-07-01

It is meaningful for tsunami assessment to evaluate phenomena beyond the design basis as well as seismic design. Because once we set the design basis tsunami height, we still have possibilities tsunami height may exceeds the determined design tsunami height due to uncertainties regarding the tsunami phenomena. Probabilistic tsunami risk assessment consists of estimating for tsunami hazard and fragility of structures and executing system analysis. In this report, we apply a method for probabilistic tsunami hazard analysis (PTHA). We introduce a logic tree approach to estimate tsunami hazard curves (relationships between tsunami height and probability of excess) and present anmore » example for Japan. Examples of tsunami hazard curves are illustrated, and uncertainty in the tsunami hazard is displayed by 5-, 16-, 50-, 84- and 95-percentile and mean hazard curves. The result of PTHA will be used for quantitative assessment of the tsunami risk for important facilities located on coastal area. Tsunami hazard curves are the reasonable input data for structures and system analysis. However the evaluation method for estimating fragility of structures and the procedure of system analysis is now being developed. (authors)« less

Pacific Basin tsunami hazards associated with mass flows in the Aleutian arc of Alaska

USGS Publications Warehouse

Waythomas, Christopher F.; Watts, Philip; Shi, Fengyan; Kirby, James T.

2009-01-01

We analyze mass-flow tsunami generation for selected areas within the Aleutian arc of Alaska using results from numerical simulation of hypothetical but plausible mass-flow sources such as submarine landslides and volcanic debris avalanches. The Aleutian arc consists of a chain of volcanic mountains, volcanic islands, and submarine canyons, surrounded by a low-relief continental shelf above about 1000–2000 m water depth. Parts of the arc are fragmented into a series of fault-bounded blocks, tens to hundreds of kilometers in length, and separated from one another by distinctive fault-controlled canyons that are roughly normal to the arc axis. The canyons are natural regions for the accumulation and conveyance of sediment derived from glacial and volcanic processes. The volcanic islands in the region include a number of historically active volcanoes and some possess geological evidence for large-scale sector collapse into the sea. Large scale mass-flow deposits have not been mapped on the seafloor south of the Aleutian Islands, in part because most of the area has never been examined at the resolution required to identify such features, and in part because of the complex nature of erosional and depositional processes. Extensive submarine landslide deposits and debris flows are known on the north side of the arc and are common in similar settings elsewhere and thus they likely exist on the trench slope south of the Aleutian Islands. Because the Aleutian arc is surrounded by deep, open ocean, mass flows of unconsolidated debris that originate either as submarine landslides or as volcanic debris avalanches entering the sea may be potential tsunami sources. To test this hypothesis we present a series of numerical simulations of submarine mass-flow initiated tsunamis from eight different source areas. We consider four submarine mass flows originating in submarine canyons and four flows that evolve from submarine landslides on the trench slope. The flows have lengths that range from 40 to 80 km, maximum thicknesses of 400–800 m, and maximum widths of 10–40 km. We also evaluate tsunami generation by volcanic debris avalanches associated with flank collapse, at four locations (Makushin, Cleveland, Seguam and Yunaska SW volcanoes), which represent large to moderate sized events in this region. We calculate tsunami sources using the numerical model TOPICS and simulate wave propagation across the Pacific using a spherical Boussinesq model, which is a modified version of the public domain code FUNWAVE. Our numerical simulations indicate that geologically plausible mass flows originating in the North Pacific near the Aleutian Islands can indeed generate large local tsunamis as well as large transoceanic tsunamis. These waves may be several meters in elevation at distal locations, such as Japan, Hawaii, and along the North and South American coastlines where they would constitute significant hazards.

A new GIS-based tsunami risk evaluation: MeTHuVA (METU tsunami human vulnerability assessment) at Yenikapı, Istanbul

NASA Astrophysics Data System (ADS)

Cankaya, Zeynep Ceren; Suzen, Mehmet Lutfi; Yalciner, Ahmet Cevdet; Kolat, Cagil; Zaytsev, Andrey; Aytore, Betul

2016-07-01

Istanbul is a mega city with various coastal utilities located on the northern coast of the Sea of Marmara. At Yenikapı, there are critical vulnerable coastal utilities, structures, and active metropolitan life. Fishery ports, commercial ports, small craft harbors, passenger terminals of intercity maritime transportation, waterfront commercial and/or recreational structures with residential/commercial areas and public utility areas are some examples of coastal utilization that are vulnerable to marine disasters. Therefore, the tsunami risk in the Yenikapı region is an important issue for Istanbul. In this study, a new methodology for tsunami vulnerability assessment for areas susceptible to tsunami is proposed, in which the Yenikapı region is chosen as a case study. Available datasets from the Istanbul Metropolitan Municipality and Turkish Navy are used as inputs for high-resolution GIS-based multi-criteria decision analysis (MCDA) evaluation of tsunami risk in Yenikapı. Bathymetry and topography database is used for high-resolution tsunami numerical modeling where the tsunami hazard, in terms of coastal inundation, is deterministically computed using the NAMI DANCE numerical code, considering earthquake worst case scenarios. In order to define the tsunami human vulnerability of the region, two different aspects, vulnerability at location and evacuation resilience maps were created using the analytical hierarchical process (AHP) method of MCDA. A vulnerability at location map is composed of metropolitan use, geology, elevation, and distance from shoreline layers, whereas an evacuation resilience map is formed by slope, distance within flat areas, distance to buildings, and distance to road networks layers. The tsunami risk map is then computed by the proposed new relationship which uses flow depth maps, vulnerability at location maps, and evacuation resilience maps.

Numerical study of breakwater failure due to tsunami-like undular bore impacts: The case of the port of Soma.

NASA Astrophysics Data System (ADS)

Martin-Medina, Manuel; Morichon, Denis; Abadie, Stephane; Le Roy, Sylvestre; Lemoine, Anne

2017-04-01

The Tohoku tsunami, that impacted the Japanese coast in 2011, caused great damages on many offshore vertical breakwaters ranging from the erosion of the rubble mound to the partial displacement or total collapse of caissons. The breakwater failure mechanisms were function of the tsunami wave types that vary along the Japanese coast according to the bathymetry features. The Iwate coast, characterized by deep water depths and steep slopes, was mainly impacted by tsunami overflow leading in particular to the failure of the world's deepest breakwater of Kamaishi. In the shallow waters of the Sendai bay, observations showed that breakwaters protecting harbor entrances were impacted by short waves train resembling to undular bore. This work aims to investigate this latter type of tsunami wave impacts that are less reported in the literature. We chose to focus on the highly damaged offshore breakwater of Soma, located in the south part of the Sendai bay. The hydrodynamics conditions during the tsunami impact are investigated using the VARANS Thetis code (Desombre et al., 2012), which allows to simulate both the free surface flow and the flow inside the rubble mound simulated by a porous medium. The model is forced at the offshore boundaries by the Funwave Boussinesq code that describes the transformation of the tsunami waves from the source to the generation of undular bores in shallow waters. The study includes the computation of forces acting on the caissons. We discuss the relevance of describing the hydrodynamics at the short wave scale to assess breakwater stability in the course of tsunami-like undular bore impact. References Desombre, J., Morichon, D., & Mory, M. (2012). SIMULTANEOUS SURFACE AND SUBSURFACE AIR AND WATER FLOWS MODELLING IN THE SWASH ZONE. Coastal Engineering Proceedings, 1(33), 56.

Tsunami-HySEA model validation for tsunami current predictions

NASA Astrophysics Data System (ADS)

Macías, Jorge; Castro, Manuel J.; González-Vida, José Manuel; Ortega, Sergio

2016-04-01

Model ability to compute and predict tsunami flow velocities is of importance in risk assessment and hazard mitigation. Substantial damage can be produced by high velocity flows, particularly in harbors and bays, even when the wave height is small. Besides, an accurate simulation of tsunami flow velocities and accelerations is fundamental for advancing in the study of tsunami sediment transport. These considerations made the National Tsunami Hazard Mitigation Program (NTHMP) proposing a benchmark exercise focussed on modeling and simulating tsunami currents. Until recently, few direct measurements of tsunami velocities were available to compare and to validate model results. After Tohoku 2011 many current meters measurement were made, mainly in harbors and channels. In this work we present a part of the contribution made by the EDANYA group from the University of Malaga to the NTHMP workshop organized at Portland (USA), 9-10 of February 2015. We have selected three out of the five proposed benchmark problems. Two of them consist in real observed data from the Tohoku 2011 event, one at Hilo Habour (Hawaii) and the other at Tauranga Bay (New Zealand). The third one consists in laboratory experimental data for the inundation of Seaside City in Oregon. Acknowledgements: This research has been partially supported by the Junta de Andalucía research project TESELA (P11-RNM7069) and the Spanish Government Research project DAIFLUID (MTM2012-38383-C02-01) and Universidad de Málaga, Campus de Excelencia Andalucía TECH. The GPU and multi-GPU computations were performed at the Unit of Numerical Methods (UNM) of the Research Support Central Services (SCAI) of the University of Malaga.

A Study of the Magnetic Fingerprint of Tsunami Induced Deposits in the Ixtapa-Zihuatanejo Area (Western Mexico)

NASA Astrophysics Data System (ADS)

Goguitchaichrili, A.; Ramirez-Herrera, M.; Calvo-Rathert, M.; Aguilar, B.; Carrancho, Alonso; Morales, J.; Caballero, C. I.; Bautista, F.

2013-05-01

The Pacific coast of Mexico has repeatedly been exposed to destructive tsunamis. Recent studies have shown that rock-magnetic methods can be a promising approach for identification of tsunami or storm induced deposits. We present new rock-magnetic and anisotropy of magnetic susceptibility results to try to distinguish tsunami deposits in the Ixtapa-Zihuatanejo area (Western Mexico). The sampled, 80 cm deep sequence is characterised by the presence of two anomalous sand beds within fine-grained coastal deposits. The first lower lying sand bed is probably associated with the 14th March 1979 Petatlán earthquake (MW = 7.6) while the second one was originated by the September 21st 1985 Mexico earthquake (MW = 8.1). Rock magnetic experiments have shown significant variations within the analysed sequence. Thermomagnetic curves reveal two types of behaviour: In the upper part of the sequence, after the occurrence of the first tsunami and in the lower part of the sequence, during that event and below. Analysis of hysteresis parameter ratios in a Day-plot also allows distinguishing two kinds of behaviour. The samples associated to the second tsunami plot in the PSD area, while specimens associated to the first tsunami and the time between both tsunamis display a very different trend which can be ascribed to the production of a considerable amount of superparamagnetic grains which might be due to pedogenic processes after the first tsunami. The studied profile is characterised by a sedimentary fabric with almost vertical minimum principal susceptibilities. The maximum susceptibility axis shows a declination angle D = 27, suggesting a NNE flow direction which is equal for both tsunamis and normal currents. The standard AMS parameters display a significant enhancement within the transitional zone between both tsunamis. The study of rock-magnetic parameters may represent a useful tool for the identification and understanding of tsunami deposits.

Detiding Tsunami Currents to Validate Velocities in Numerical Simulation Codes using Observations Near Hawaii from the 2011 Tohoku Tsunami

NASA Astrophysics Data System (ADS)

Adams, L. M.; LeVeque, R. J.

2015-12-01

The ability to measure, predict, and compute tsunami flow velocities is ofimportance in risk assessment and hazard mitigation. Until recently, fewdirect measurements of tsunami velocities existed to compare with modelresults. During the 11 March 2001 Tohoku Tsunami, 328 current meters werewere in place around the Hawaiian Islands, USA, that captured time seriesof water velocity in 18 locations, in both harbors and deep channels, ata series of depths. Arcos and LeVeque[1] compared these records againstnumerical simulations performed using the GeoClaw numerical tsunami modelwhich is based on the depth-averaged shallow water equations. They confirmedthat GeoClaw can accurately predict velocities at nearshore locations, andthat tsunami current velocity is more spatially variable than wave formor height and potentially more sensitive for model validation.We present a new approach to detiding this sensitive current data. Thisapproach can be used separately on data at each depth of a current gauge.When averaged across depths, the Geoclaw results in [1] are validated. Withoutaveraging, the results should be useful to researchers wishing to validate their3D codes. These results can be downloaded from the project website below.The approach decomposes the pre-tsunami component of the data into three parts:a tidal component, a fast component (noise), and a slow component (not matchedby the harmonic analysis). Each part is extended to the time when the tsunamiis present and subtracted from the current data then to give the ''tsunami current''that can be compared with 2D or 3D codes that do not model currents in thepre-tsunami regime. [1] "Validating Velocities in the GeoClaw Tsunami Model using Observations NearHawaii from the 2001 Tohoku Tsunami"M.E.M. Arcos and Randall J. LeVequearXiv:1410.2884v1 [physics.geo-py], 10 Oct. 2014.project website: http://faculty.washington.edu/lma3/research.html

A Preliminary Tsunami Vulnerability Analysis for Yenikapi Region in Istanbul

NASA Astrophysics Data System (ADS)

Ceren Cankaya, Zeynep; Suzen, Lutfi; Cevdet Yalciner, Ahmet; Kolat, Cagil; Aytore, Betul; Zaytsev, Andrey

2015-04-01

One of the main requirements during post disaster recovery operations is to maintain proper transportation and fluent communication at the disaster areas. Ports and harbors are the main transportation hubs which must work with proper performance at all times especially after the disasters. Resilience of coastal utilities after earthquakes and tsunamis have major importance for efficient and proper rescue and recovery operations soon after the disasters. Istanbul is a mega city with its various coastal utilities located at the north coast of the Sea of Marmara. At Yenikapi region of Istanbul, there are critical coastal utilities and vulnerable coastal structures and critical activities occur daily. Fishery ports, commercial ports, small craft harbors, passenger terminals of intercity maritime transportation, water front commercial and/or recreational structures are some of the examples of coastal utilization which are vulnerable against marine disasters. Therefore their vulnerability under tsunami or any other marine hazard to Yenikapi region of Istanbul is an important issue. In this study, a methodology of vulnerability analysis under tsunami attack is proposed with the applications to Yenikapi region. In the study, high resolution (1m) GIS database of Istanbul Metropolitan Municipality (IMM) is used and analyzed by using GIS implementation. The bathymetry and topography database and the vector dataset containing all buildings/structures/infrastructures in the study area are obtained for tsunami numerical modeling for the study area. GIS based tsunami vulnerability assessment is conducted by applying the Multi-criteria Decision Making Analysis (MCDA). The tsunami parameters from deterministically defined worst case scenarios are computed from the simulations using tsunami numerical model NAMI DANCE. The vulnerability parameters in the region due to two different classifications i) vulnerability of buildings/structures and ii) vulnerability of (human) evacuation are defined and scored. The risk level is computed using tsunami intensity (level of flow depth from simulations) and vulnerability (structural and human-based) at each node in Yenikapi. The results are presented at high resolution (1m) and discussed. Acknowledgements: Partial support by EU 603839 ASTARTE Project, UDAP-C-12-14 of AFAD of Turkey, 108Y227 and 113M556 of TUBITAK Turkey, RAPSODI (CONCERT_Dis-021) of CONCERT-Japan Joint Call, 2011K140210 of DPT, Istanbul Metropolitan Municipality, Japan-Turkey Joint Research Project by JICA on earthquakes and tsunamis in Marmara Region by SATREPS are acknowledged.

Modelling tsunami inundation for risk analysis at the Andaman Sea Coast of Thailand

NASA Astrophysics Data System (ADS)

Kaiser, G.; Kortenhaus, A.

2009-04-01

The mega-tsunami of Dec. 26, 2004 strongly impacted the Andaman Sea coast of Thailand and devastated coastal ecosystems as well as towns, settlements and tourism resorts. In addition to the tragic loss of many lives, the destruction or damage of life-supporting infrastructure, such as buildings, roads, water & power supply etc. caused high economic losses in the region. To mitigate future tsunami impacts there is a need to assess the tsunami hazard and vulnerability in flood prone areas at the Andaman Sea coast in order to determine the spatial distribution of risk and to develop risk management strategies. In the bilateral German-Thai project TRAIT research is performed on integrated risk assessment for the Provinces Phang Nga and Phuket in southern Thailand, including a hazard analysis, i.e. modelling tsunami propagation to the coast, tsunami wave breaking and inundation characteristics, as well as vulnerability analysis of the socio-economic and the ecological system in order to determine the scenario-based, specific risk for the region. In this presentation results of the hazard analysis and the inundation simulation are presented and discussed. Numerical modelling of tsunami propagation and inundation simulation is an inevitable tool for risk analysis, risk management and evacuation planning. While numerous investigations have been made to model tsunami wave generation and propagation in the Indian Ocean, there is still a lack in determining detailed inundation patterns, i.e. water depth and flow dynamics. However, for risk management and evacuation planning this knowledge is essential. As the accuracy of the inundation simulation is strongly depending on the available bathymetric and the topographic data, a multi-scale approach is chosen in this work. The ETOPO Global Relief Model as a bathymetric basis and the Shuttle Radar Topography Mission (SRTM90) have been widely applied in tsunami modelling approaches as these data are free and almost world-wide available. However, to model tsunami-induced inundation for risk analysis and management purposes the accuracy of these data is not sufficient as the processes in the near-shore zone cannot be modelled accurately enough and the spatial resolution of the topography is weak. Moreover, the SRTM data provide a digital surface model which includes vegetation and buildings in the surface description. To improve the data basis additional bathymetric data were used in the near shore zone of the Phang Nga and Phuket coastlines and various remote sensing techniques as well as additional GPS measurements were applied to derive a high resolution topography from satellite and airborne data. Land use classifications and filter methods were developed to correct the digital surface models to digital elevation models. Simulations were then performed with a non-linear shallow water model to model the 2004 Asian Tsunami and to simulate possible future ones. Results of water elevation near the coast were compared with field measurements and observations, and the influence of the resolution of the topography on inundation patterns like water depth, velocity, dispersion and duration of the flood were analysed. The inundation simulation provides detailed hazard maps and is considered a reliable basis for risk assessment and risk zone mapping. Results are regarded vital for estimation of tsunami induced damages and evacuation planning. Results of the aforementioned simulations will be discussed during the conference. Differences of the numerical results using topographic data of different scales and modified by different post processing techniques will be analysed and explained. Further use of the results with respect to tsunami risk analysis and management will also be demonstrated.

Defining Tsunami Magnitude as Measure of Potential Impact

NASA Astrophysics Data System (ADS)

Titov, V. V.; Tang, L.

2016-12-01

The goal of tsunami forecast, as a system for predicting potential impact of a tsunami at coastlines, requires quick estimate of a tsunami magnitude. This goal has been recognized since the beginning of tsunami research. The work of Kajiura, Soloviev, Abe, Murty, and many others discussed several scales for tsunami magnitude based on estimates of tsunami energy. However, difficulties of estimating tsunami energy based on available tsunami measurements at coastal sea-level stations has carried significant uncertainties and has been virtually impossible in real time, before tsunami impacts coastlines. The slow process of tsunami magnitude estimates, including collection of vast amount of available coastal sea-level data from affected coastlines, made it impractical to use any tsunami magnitude scales in tsunami warning operations. Uncertainties of estimates made tsunami magnitudes difficult to use as universal scale for tsunami analysis. Historically, the earthquake magnitude has been used as a proxy of tsunami impact estimates, since real-time seismic data is available of real-time processing and ample amount of seismic data is available for an elaborate post event analysis. This measure of tsunami impact carries significant uncertainties in quantitative tsunami impact estimates, since the relation between the earthquake and generated tsunami energy varies from case to case. In this work, we argue that current tsunami measurement capabilities and real-time modeling tools allow for establishing robust tsunami magnitude that will be useful for tsunami warning as a quick estimate for tsunami impact and for post-event analysis as a universal scale for tsunamis inter-comparison. We present a method for estimating the tsunami magnitude based on tsunami energy and present application of the magnitude analysis for several historical events for inter-comparison with existing methods.

Hydraulic experiment on formation mechanism of tsunami deposit and verification of sediment transport model for tsunamis

NASA Astrophysics Data System (ADS)

Yamamoto, A.; Takahashi, T.; Harada, K.; Sakuraba, M.; Nojima, K.

2017-12-01

An underestimation of the 2011 Tohoku tsunami caused serious damage in coastal area. Reconsideration for tsunami estimation needs knowledge of paleo tsunamis. The historical records of giant tsunamis are limited, because they had occurred infrequently. Tsunami deposits may include many of tsunami records and are expected to analyze paleo tsunamis. However, present research on tsunami deposits are not able to estimate the tsunami source and its magnitude. Furthermore, numerical models of tsunami and its sediment transport are also important. Takahashi et al. (1999) proposed a model of movable bed condition due to tsunamis, although it has some issues. Improvement of the model needs basic data on sediment transport and deposition. This study investigated the formation mechanism of tsunami deposit by hydraulic experiment using a two-dimensional water channel with slope. In a fixed bed condition experiment, velocity, water level and suspended load concentration were measured at many points. In a movable bed condition, effects of sand grains and bore wave on the deposit were examined. Yamamoto et al. (2016) showed deposition range varied with sand grain sizes. In addition, it is revealed that the range fluctuated by number of waves and wave period. The measurements of velocity and water level showed that flow was clearly different near shoreline and in run-up area. Large velocity by return flow was affected the amount of sand deposit near shoreline. When a cutoff wall was installed on the slope, the amount of sand deposit repeatedly increased and decreased. Especially, sand deposit increased where velocity decreased. Takahashi et al. (1999) adapted the proposed model into Kesennuma bay when the 1960 Chilean tsunami arrived, although the amount of sand transportation was underestimated. The cause of the underestimation is inferred that the velocity of this model was underestimated. A relationship between velocity and sediment transport has to be studied in detail, but observation of velocity in Kesennnuma bay had a low accuracy. On the other hand, this hydraulic experiment measured accurate velocity and sand deposition distribution of various condition. Based on these data, we tried more accurate verification of the model of Takahashi et al. (1999).

Hydrodynamic implications of textural trends in sand deposits of the 2004 tsunami in Sri Lanka

USGS Publications Warehouse

Morton, R.A.; Goff, J.R.; Nichol, S.L.

2008-01-01

Field observations and sediment samples at a coastal-plain setting in southeastern Sri Lanka were used to document the erosional and depositional impacts of the 2004 Indian Ocean tsunami and to interpret the hydrodynamic processes that produced an extensive sand-sheet deposit. Tsunami deposit thicknesses ranged from 6 to 22??cm with thickness being controlled partly by antecedent topography. The deposit was composed of coarse to medium sand organized into plane-parallel laminae and a few laminasets. Vertical textural trends showed an overall but non-systematic upward fining and upward thinning of depositional units with an upward increase in heavy-mineral laminations at some locations. Repeated patterns in the vertical textural trends (upward fining, upward coarsening, uniform) were used to subdivide and correlate the deposit into five hydro-textural stratigraphic units. The depositional units were linked to hydrodynamic processes and upcurrent conditions, such as rates of sediment supply and composition of the sediment sources. Vertical changes in grain-size distributions recorded the depositional phases associated with flow acceleration, initial unsteady pulsating flow, relatively stable and uniform flow, flow deceleration, slack water, and return flow or flow redirection. Study results suggest that vertical textural trends from multiple cross-shore sections can be used to interpret complex tsunami flow histories, but at the location examined, interpretation of the lateral textural trends did not provide a basis for identifying the correct sediment transport pathways because flow near the landward boundary was multidirectional.

Mathematical modelling of tsunami impacts on critical infrastructures: exposure and severity associated with debris transport at Sines port, Portugal.

NASA Astrophysics Data System (ADS)

Conde, Daniel; Baptista, Maria Ana; Sousa Oliveira, Carlos; Ferreira, Rui M. L.

2015-04-01

Global energy production is still significantly dependant on the coal supply chain, justifying huge investments on building infrastructures, capable of stocking very large quantities of this natural resource. Most of these infrastructures are located at deep-sea ports and are therefore exposed to extreme coastal hazards, such as tsunami impacts. The 2011 Tohoku tsunami is reported to have inflicted severe damage to Japan's coal-fired power stations and related infrastructure. Sines, located in the Portuguese coast, hosts a major commercial port featuring an exposed coal stockpile area extending over more than 24 ha and a container terminal currently under expansion up to 100ha. It is protected against storm surges but tsunamis have not been considered in the design criteria. The dominant wind-generated wave direction is N to NW, while the main tsunamigenic faults are located S to SW of the port. This configuration potentially exposes sensitive facilities, such as the new terminal container and the coal stockpile area. According to a recent revision of the national tsunami catalogue (Baptista, 2009), Portugal has been affected by numerous major tsunamis over the last two millennia, with the most notorious event being the Great Lisbon Earthquake and Tsunami occurred on the 1st November 1755. The aim of this work is to simulate the open ocean propagation and overland impact of a tsunami on the Sines port, similar to the historical event of 1755, based on the different tsunamigenic faults and magnitudes proposed in the current literature. Open ocean propagation was modelled with standard simulation tools like TUNAMI and GeoClaw. Near-shore and overland propagation was carried out using a recent 2DH mathematical model for solid-fluid flows, STAV-2D from CERIS-IST (Ferreira et al., 2009; Canelas, 2013). STAV-2D is particularly suited for tsunami propagation over complex and morphodynamic geometries, featuring a discretization scheme based on a finite-volume method using a flux-splitting technique with a reviewed Roe-Riemann solver and appropriate source-term formulations to ensure full conservativeness. Additionally, STAV-2D features Lagrangian-Eulerian coupling enabling solid transport simulation under both continuum and discrete approaches, and has been validated with both laboratory data and paleo-tsunami evidence (Conde, 2013a; Conde, 2013b). The interactions between the inundating flow and coal stockpiles or natural mobile bed reaches were simulated using a continuum debris-flow approach, featuring fractional solid transport, while the containers at the new terminal were advected with an explicit Lagrangian method. The meshwork employed at the port models the existing geometry and structures in great detail, enabling explicitly resolved interactions between the current infrastructure and the overland propagating tsunami. The obtained preliminary results suggest that several structures, some of them critical in a nationwide context, are exposed to tsunami actions. The coal deposition pattern and the final location of monitored containers were determined for two magnitude scenarios (8.5 Mw and 9.5 Mw) in the case of a tsunami generated at the Horseshoe fault and one magnitude scenario (9.5 Mw) for a tsunami generated at the Gorringe bank. The inland washing of the coal stockpiles may impose great loss of both economical and environmental value, while the impact of large mobile debris, such as the containers in the terminal area, significantly increases the severity of infrastructural damage. Acknowledgements This work was partially funded by FEDER, program COMPETE, and by national funds through the Portuguese Foundation for Science and Technology (FCT) with project RECI/ECM-HID/0371/2012. References Baptista M.A. & Miranda, J.M. (2009), Revision of the Portuguese catalog of tsunamis. Nat. Hazards Earth Syst. Sci., 9, 25-42. Canelas, R.; Murillo, J. & Ferreira, R.M.L. (2013), Two-dimensional depth-averaged modelling of dam-break flows over mobile beds. Vol 51(4) pp. 392-407. Conde, D. A. S.; Baptista, M. A. V.; Sousa Oliveira, C. & Ferreira, R. M. L. (2013a), A shallow-flow model for the propagation of tsunamis over complex geometries and mobile beds, Nat. Hazards Earth Syst. Sci., 13, 2533-2542. Conde, D. A. S.; Canelas, R. B.; Sousa Oliveira, C. & Ferreira, R. M. L. (2013b), Mathematical modelling of transport of coal stockpiles by a tsunami at Sines port, 8th International SedNet Conference 2013, Lisbon, Portugal. Ferreira, R. M. L.; Franca, M. J.; Leal, J. G. & Cardoso, A. H. (2009), Mathematical modelling of shallow flows: Closure models drawn from grain-scale mechanics of sediment transport and flow hydrodynamics, Can. J. Civil. Eng., 36, 1604-1621, 2009.

Tsunami Waves Joint Inversion Using Tsunami Inundation, Tsunami Deposits Distribution and Marine-Terrestrial Sediment Signal in Tsunami Deposit

NASA Astrophysics Data System (ADS)

Tang, H.; WANG, J.

2017-12-01

Population living close to coastlines is increasing, which creates higher risks due to coastal hazards, such as the tsunami. However, the generation of a tsunami is not fully understood yet, especially for paleo-tsunami. Tsunami deposits are one of the concrete evidence in the geological record which we can apply for studying paleo-tsunami. The understanding of tsunami deposits has significantly improved over the last decades. There are many inversion models (e.g. TsuSedMod, TSUFLIND, and TSUFLIND-EnKF) to study the overland-flow characteristics based on tsunami deposits. However, none of them tries to reconstruct offshore tsunami wave characteristics (wave form, wave height, and length) based on tsunami deposits. Here we present a state-of-the-art inverse approach to reconstruct offshore tsunami wave based on the tsunami inundation data, the spatial distribution of tsunami deposits and Marine-terrestrial sediment signal in the tsunami deposits. Ensemble Kalman Filter (EnKF) Method is used for assimilating both sediment transport simulations and the field observation data. While more computationally expensive, the EnKF approach potentially provides more accurate reconstructions for tsunami waveform. In addition to the improvement of inversion results, the ensemble-based method can also quantify the uncertainties of the results. Meanwhile, joint inversion improves the resolution of tsunami waves compared with inversions using any single data type. The method will be tested by field survey data and gauge data from the 2011 Tohoku tsunami on Sendai plain area.

Coastal changes in the Sendai area from the impact of the 2011 Tōhoku-oki tsunami: Interpretations of time series satellite images, helicopter-borne video footage and field observations

NASA Astrophysics Data System (ADS)

Tappin, David R.; Evans, Hannah M.; Jordan, Colm J.; Richmond, Bruce; Sugawara, Daisuke; Goto, Kazuhisa

2012-12-01

A combination of time-series satellite imagery, helicopter-borne video footage and field observation is used to identify the impact of a major tsunami on a low-lying coastal zone located in eastern Japan. A comparison is made between the coast protected by armoured 'engineered' sea walls and the coast without. Changes are mapped from before and after imagery, and sedimentary processes identified from the video footage. The results are validated by field observations. The impact along a 'natural' coast, with minimal defences, is erosion focussed on the back beach. Along coasts with hard engineered protection constructed to defend against erosion, the presence of three to six metre high concrete-faced embankments results in severe erosion on their landward faces. The erosion is due to the tsunami wave accelerating through a hydraulic jump as it passes over the embankment, resulting in the formation of a ditch into which the foundations collapse. Engineered coastal defences are thus found to be small defence against highly energetic tsunami waves that overtop them. There is little erosion (or sedimentation) of the whole beach, and where active, it mainly forms V-shaped channels. These channels are probably initiated during tsunami inflow and then further developed during tsunami backflow. Tsunami backflow on such a low lying area takes place energetically as sheet flow immediately after tsunami flooding has ceased. Subsequently, when the water level landward of the coastal dune ridges falls below their elevation, flow becomes confined to rivers and breaches in the coast formed during tsunami inflow. Enigmatic, short lived, 'strand lines' are attributed to the slow fall of sea level after such a major tsunami. Immediately after the tsunami coastal reconstruction begins, sourced from the sediment recently flushed into the sea by tsunami backflow.

Scenario-based numerical modelling and the palaeo-historic record of tsunamis in Wallis and Futuna, Southwest Pacific

NASA Astrophysics Data System (ADS)

Lamarche, G.; Popinet, S.; Pelletier, B.; Mountjoy, J.; Goff, J.; Delaux, S.; Bind, J.

2015-08-01

We investigated the tsunami hazard in the remote French territory of Wallis and Futuna, Southwest Pacific, using the Gerris flow solver to produce numerical models of tsunami generation, propagation and inundation. Wallis consists of the inhabited volcanic island of Uvéa that is surrounded by a lagoon delimited by a barrier reef. Futuna and the island of Alofi form the Horn Archipelago located ca. 240 km east of Wallis. They are surrounded by a narrow fringing reef. Futuna and Alofi emerge from the North Fiji Transform Fault that marks the seismically active Pacific-Australia plate boundary. We generated 15 tsunami scenarios. For each, we calculated maximum wave elevation (MWE), inundation distance and expected time of arrival (ETA). The tsunami sources were local, regional and distant earthquake faults located along the Pacific Rim. In Wallis, the outer reef may experience 6.8 m-high MWE. Uvéa is protected by the barrier reef and the lagoon, but inundation depths of 2-3 m occur in several coastal areas. In Futuna, flow depths exceeding 2 m are modelled in several populated areas, and have been confirmed by a post-September 2009 South Pacific tsunami survey. The channel between the islands of Futuna and Alofi amplified the 2009 tsunami, which resulted in inundation distance of almost 100 m and MWE of 4.4 m. This first ever tsunami hazard modelling study of Wallis and Futuna compares well with palaeotsunamis recognised on both islands and observation of the impact of the 2009 South Pacific tsunami. The study provides evidence for the mitigating effect of barrier and fringing reefs from tsunamis.

Scenario-based numerical modelling and the palaeo-historic record of tsunamis in Wallis and Futuna, Southwest Pacific

NASA Astrophysics Data System (ADS)

Lamarche, G.; Popinet, S.; Pelletier, B.; Mountjoy, J.; Goff, J.; Delaux, S.; Bind, J.

2015-04-01

We investigated the tsunami hazard in the remote French territory of Wallis and Futuna, Southwest Pacific, using the Gerris flow solver to produce numerical models of tsunami generation, propagation and inundation. Wallis consists of the inhabited volcanic island of Uvéa that is surrounded by a lagoon delimited by a barrier reef. Futuna and the island of Alofi forms the Horn Archipelago located ca. 240 km east of Wallis. They are surrounded by a narrow fringing reef. Futuna and Alofi emerge from the North Fiji Transform Fault that marks the seismically active Pacific-Australia plate boundary. We generated fifteen tsunami scenarios. For each, we calculated maximum wave elevation (MWE), inundation distance, and Expected Time of Arrival (ETA). The tsunami sources were local, regional and distant earthquake faults located along the Pacific Rim. In Wallis, the outer reef may experience 6.8 m-high MWE. Uvéa is protected by the barrier reef and the lagoon, but inundation depths of 2-3 m occur in several coastal areas. In Futuna, flow depths exceeding 2 m are modelled in several populated areas, and have been confirmed by a post-September 2009 South Pacific tsunami survey. The channel between the islands of Futuna and Alofi amplified the 2009 tsunami, which resulted in inundation distance of almost 100 m and MWE of 4.4 m. This first-ever tsunami hazard modelling study of Wallis and Futuna compares well with palaeotsunamis recognised on both islands and observation of the impact of the 2009 South Pacific tsunami. The study provides evidence for the mitigating effect of barrier and fringing reefs from tsunamis.

Issues and Advances in Understanding Landslide-Generated Tsunamis: Toward a Unified Model

NASA Astrophysics Data System (ADS)

Geist, E. L.; Locat, J.; Lee, H. J.; Lynett, P. J.; Parsons, T.; Kayen, R. E.; Hart, P. E.

2008-12-01

The physics of tsunamis generated from submarine landslides is highly complex, involving a cross- disciplinary exchange in geophysics. In the 10 years following the devastating Papua New Guinea tsunami, there have been significant advances in understanding landslide-generated tsunamis. However, persistent issues still remain related to submarine landslide dynamics that may be addressed with collection of new marine geologic and geophysical observations. We review critical elements of landslide tsunamis in the hope of developing a unified model that encompasses all stages of the process from triggering to tsunami runup. Because the majority of non-volcanogenic landslides that generate tsunamis are triggered seismically, advances in understanding inertial displacements and changes in strength and rheologic properties in response to strong-ground motion need to be included in a unified model. For example, interaction between compliant marine sediments and multi-direction ground motion results in greater permanent plastic displacements than predicted by traditional rigid-block analysis. When considering the coupling of the overlying water layer in the generation of tsunamis, the post-failure dynamics of landslides is important since the overall rate of seafloor deformation for landslides is less than or comparable to the phase speed of tsunami waves. As such, the rheologic and mechanical behavior of the slide material needs to be well understood. For clayey and silty debris flows, a non-linear (Herschel-Bulkley) and bilinear rheology have recently been developed to explain observed runout distances and deposit thicknesses. An additional complexity to this rheology is the inclusion of hydrate-laden sediment that commonly occurs along continental slopes. Although it has been proposed in the past that gas hydrate dissociation may provide potential failure planes for slide movement, it is unclear how zones of rigid hydrate-bearing sediment surrounded by a more viscoplastic matrix affects the overall rheologic behavior during slide dynamics. For more rigid materials, such as carbonate and volcanic rocks, models are being developed that encompass the initial fracturing and eventual disintegration associated with debris avalanches. Lastly, the physics dictating the hydrodynamics of landslide-generated tsunamis is equally complex. The effects of non-linearity and dispersion are not necessarily negligible for landslides (in contrast to most earthquake-generated tsunamis), indicating that numerical implementation of the non-linear Boussinesq equations is often needed. Moreover, we show that for near-field landslide tsunamis propagating across the continental shelf, bottom friction (bottom boundary layer turbulence) and wave breaking can be important energy sinks. Detailed geophysical surveys can dissect landslide complexes to determine the geometry of individual events and help estimate rheological properties of the flowing mass, whereas cores in landslide provinces can determine the mechanical properties and pore-pressure distribution for pre- and post-failure sediment. This information is critical toward developing well-documented case histories for validating physics-based landslide tsunami models.

Tsunami Casualty Model

NASA Astrophysics Data System (ADS)

Yeh, H.

2007-12-01

More than 4500 deaths by tsunamis were recorded in the decade of 1990. For example, the 1992 Flores Tsunami in Indonesia took away at least 1712 lives, and more than 2182 people were victimized by the 1998 Papua New Guinea Tsunami. Such staggering death toll has been totally overshadowed by the 2004 Indian Ocean Tsunami that claimed more than 220,000 lives. Unlike hurricanes that are often evaluated by economic losses, death count is the primary measure for tsunami hazard. It is partly because tsunamis kill more people owing to its short lead- time for warning. Although exact death tallies are not available for most of the tsunami events, there exist gender and age discriminations in tsunami casualties. Significant gender difference in the victims of the 2004 Indian Ocean Tsunami was attributed to women's social norms and role behavior, as well as cultural bias toward women's inability to swim. Here we develop a rational casualty model based on humans' limit to withstand the tsunami flows. The application to simple tsunami runup cases demonstrates that biological and physiological disadvantages also make a significant difference in casualty rate. It further demonstrates that the gender and age discriminations in casualties become most pronounced when tsunami is marginally strong and the difference tends to diminish as tsunami strength increases.

A computationally fast, reduced model for simulating landslide dynamics and tsunamis generated by landslides in natural terrains

NASA Astrophysics Data System (ADS)

Mohammed, F.

2016-12-01

Landslide hazards such as fast-moving debris flows, slow-moving landslides, and other mass flows cause numerous fatalities, injuries, and damage. Landslide occurrences in fjords, bays, and lakes can additionally generate tsunamis with locally extremely high wave heights and runups. Two-dimensional depth-averaged models can successfully simulate the entire lifecycle of the three-dimensional landslide dynamics and tsunami propagation efficiently and accurately with the appropriate assumptions. Landslide rheology is defined using viscous fluids, visco-plastic fluids, and granular material to account for the possible landslide source materials. Saturated and unsaturated rheologies are further included to simulate debris flow, debris avalanches, mudflows, and rockslides respectively. The models are obtained by reducing the fully three-dimensional Navier-Stokes equations with the internal rheological definition of the landslide material, the water body, and appropriate scaling assumptions to obtain the depth-averaged two-dimensional models. The landslide and tsunami models are coupled to include the interaction between the landslide and the water body for tsunami generation. The reduced models are solved numerically with a fast semi-implicit finite-volume, shock-capturing based algorithm. The well-balanced, positivity preserving algorithm accurately accounts for wet-dry interface transition for the landslide runout, landslide-water body interface, and the tsunami wave flooding on land. The models are implemented as a General-Purpose computing on Graphics Processing Unit-based (GPGPU) suite of models, either coupled or run independently within the suite. The GPGPU implementation provides up to 1000 times speedup over a CPU-based serial computation. This enables simulations of multiple scenarios of hazard realizations that provides a basis for a probabilistic hazard assessment. The models have been successfully validated against experiments, past studies, and field data for landslides and tsunamis.

Integrated Historical Tsunami Event and Deposit Database

NASA Astrophysics Data System (ADS)

Dunbar, P. K.; McCullough, H. L.

2010-12-01

The National Geophysical Data Center (NGDC) provides integrated access to historical tsunami event, deposit, and proxy data. The NGDC tsunami archive initially listed tsunami sources and locations with observed tsunami effects. Tsunami frequency and intensity are important for understanding tsunami hazards. Unfortunately, tsunami recurrence intervals often exceed the historic record. As a result, NGDC expanded the archive to include the Global Tsunami Deposits Database (GTD_DB). Tsunami deposits are the physical evidence left behind when a tsunami impacts a shoreline or affects submarine sediments. Proxies include co-seismic subsidence, turbidite deposits, changes in biota following an influx of marine water in a freshwater environment, etc. By adding past tsunami data inferred from the geologic record, the GTD_DB extends the record of tsunamis backward in time. Although the best methods for identifying tsunami deposits and proxies in the geologic record remain under discussion, developing an overall picture of where tsunamis have affected coasts, calculating recurrence intervals, and approximating runup height and inundation distance provides a better estimate of a region’s true tsunami hazard. Tsunami deposit and proxy descriptions in the GTD_DB were compiled from published data found in journal articles, conference proceedings, theses, books, conference abstracts, posters, web sites, etc. The database now includes over 1,200 descriptions compiled from over 1,100 citations. Each record in the GTD_DB is linked to its bibliographic citation where more information on the deposit can be found. The GTD_DB includes data for over 50 variables such as: event description (e.g., 2010 Chile Tsunami), geologic time period, year, deposit location name, latitude, longitude, country, associated body of water, setting during the event (e.g., beach, lake, river, deep sea), upper and lower contacts, underlying and overlying material, etc. If known, the tsunami source mechanism (e.g., earthquake, landslide, volcanic eruption, asteroid impact) is also specified. Observations (grain size, sedimentary structure, bed thickness, number of layers, etc.) are stored along with the conclusions drawn from the evidence by the author (wave height, flow depth, flow velocity, number of waves, etc.). Geologic time periods in the GTD_DB range from Precambrian to Quaternary, but the majority (70%) are from the Quaternary period. This period includes events such as: the 2004 Indian Ocean tsunami, the Cascadia subduction zone earthquakes and tsunamis, the 1755 Lisbon tsunami, the A.D. 79 Vesuvius tsunami, the 3500 BP Santorini caldera collapse and tsunami, and the 7000 BP Storegga landslide-generated tsunami. Prior to the Quaternary period, the majority of the paleotsunamis are due to impact events such as: the Tertiary Chesapeake Bay Bolide, Cretaceous-Tertiary (K/T) Boundary, Cretaceous Manson, and Devonian Alamo. The tsunami deposits are integrated with the historical tsunami event database where applicable. For example, users can search for articles describing deposits related to the 1755 Lisbon tsunami and view those records, as well as link to the related historic event record. The data and information may be viewed using tools designed to extract and display data (selection forms, Web Map Services, and Web Feature Services).

Probabilistic analysis of tsunami hazards

USGS Publications Warehouse

Geist, E.L.; Parsons, T.

2006-01-01

Determining the likelihood of a disaster is a key component of any comprehensive hazard assessment. This is particularly true for tsunamis, even though most tsunami hazard assessments have in the past relied on scenario or deterministic type models. We discuss probabilistic tsunami hazard analysis (PTHA) from the standpoint of integrating computational methods with empirical analysis of past tsunami runup. PTHA is derived from probabilistic seismic hazard analysis (PSHA), with the main difference being that PTHA must account for far-field sources. The computational methods rely on numerical tsunami propagation models rather than empirical attenuation relationships as in PSHA in determining ground motions. Because a number of source parameters affect local tsunami runup height, PTHA can become complex and computationally intensive. Empirical analysis can function in one of two ways, depending on the length and completeness of the tsunami catalog. For site-specific studies where there is sufficient tsunami runup data available, hazard curves can primarily be derived from empirical analysis, with computational methods used to highlight deficiencies in the tsunami catalog. For region-wide analyses and sites where there are little to no tsunami data, a computationally based method such as Monte Carlo simulation is the primary method to establish tsunami hazards. Two case studies that describe how computational and empirical methods can be integrated are presented for Acapulco, Mexico (site-specific) and the U.S. Pacific Northwest coastline (region-wide analysis).

Role of Compressibility on Tsunami Propagation

NASA Astrophysics Data System (ADS)

Abdolali, Ali; Kirby, James T.

2017-12-01

In the present paper, we aim to reduce the discrepancies between tsunami arrival times evaluated from tsunami models and real measurements considering the role of ocean compressibility. We perform qualitative studies to reveal the phase speed reduction rate via a modified version of the Mild Slope Equation for Weakly Compressible fluid (MSEWC) proposed by Sammarco et al. (2013). The model is validated against a 3-D computational model. Physical properties of surface gravity waves are studied and compared with those for waves evaluated from an incompressible flow solver over realistic geometry for 2011 Tohoku-oki event, revealing reduction in phase speed.