ANALISA NUMERIK TSUNAMI PANGANDARAN DAN IMPLIKASINYA TERHADAP MITIGASI BENCANA

Lempeng Eurasia adalah lempeng tektonik terbesar ketiga yang berada di daerah Eurasia, daratan yang terdiri dari benua Eropa dan Asia. Lempeng Sunda merupakan bagian dari Lempeng Eurasia yang rumit secara tektonik dan aktif secara seismik.Adapun tujuan penelitian ini adalah untuk menentukan karakterisik pola patahan akibat gempabumi tanggal 17 Juli 2006 di Laut Selatan Jawa dengan sumber data dari katalog gempa bumi USGS. Analisis bola fokus bahwa gempa tanggal 17 Juli 2006 dengan koordinat 9.3° S dan 107.4° E adalah kombinasi sesar mendatar dan sesar naik atau jenis sesar ini disebut juga oblique. Hasil analisis 3D Focal Mechanism dan perhitungan rumus empiris menunjukkan bahwa terjadinya penjalaran gelombang tsunami (Tsunami Travel Time) kedaerah pantai dipesisir Jawa selatan mempunyai waktu sekitar 30 menit, sehingga diperlukan kesiapsiagaan dalam menghadapi bencana. The Eurasian Plate is the third largest tectonic plate in the Eurasia region, a land consisting of Europe and Asia. The Sunda Plate is part of the Eurasian Plate which is complicated by tectonics and seismically active. The purpose of this study is to determine the characteristics of the fault patterns due to the earthquake on 17 July 2006 in the South Sea of Java with data sources from the USGS earthquake catalog. Focus ball analysis that the earthquake on July 17, 2006 with coordinates 9.3° S and 107.4° E is a combination of horizontal faults and rising faults or this type of fault is also called oblique. The results of the 3D Focal Me chanism analysis and the calculation of empirical formulas indicate that the occurrence of tsunami wave propagation in the coastal areas of South Java approximately 30 minutes, so that preparedness is needed in the face of disasters.

Short-term forecast of local tsunamis based on data containing seismic noise from deep-ocean stations closest to the sources

Reliable short-term tsunami forecast on the Kuril Islands when earthquakes occur in the Kuril-Kamchatka Trench is the most difficult. Forecasting by the traditional magnitude method often leads to false tsunami alarms. Based on the examples of the events of 2006, 2007 and 2020 on the Kuril Islands, as well as the event of 2018 in Alaska, it was shown that according to the data of the ocean level measuring stations closest to the tsunami source (tsunami travel time is 10–20 minutes) it is possible to adequately predict the tsunami near the coast. Calculations of tsunami waveforms near the coast from data containing seismic noise have shown that the resulting waveforms contain high-frequency oscillations. However, these fluctuations do not interfere with the assessment of the real waveform and the danger of the expected tsunami. In contrast to forecast methods based on the magnitude criterion, the applied method of short-term tsunami forecast makes it possible to calculate the waveform: the amplitudes of the first, maximum waves, their arrival time at a given point and the estimated duration of the tsunami. The proposed method can become a tool that will improve the quality of operational tsunami warning, significantly reducing the number of false tsunami alarms.

Reanalysis of the 1761 transatlantic tsunami

The tsunami catalogues of the Atlantic include two transatlantic tsunamis in the 18th century the extensively studied 1st November 1755, and 31st March 1761. The latest event struck Portugal, Spain, and Morocco around noontime. Several sources report a tsunami following the earthquake as far as Cornwall (United Kingdom), Cork (Ireland) and Barbados (Caribbean). An earlier analysis of macroseismic information and its compatibility with tsunami travel time information located the epicentre circa 34.5° N 13° W close to the Ampere Seamount at the eastern end of the Gloria Fault (North East Atlantic). The estimated magnitude of the earthquake is 8.5. In this study, we propose a tectonic source for the 31st March 1761 earthquake compatible with the tsunami observations in the Atlantic. We revisit the tsunami observations, reevaluate tsunami travel time data, and include a report from Cadiz not used before. The global plate kinematic model NUVEL 1A computes a convergence rate of 3.8 mm/y in the area of the presumed epicentre. We propose a source mechanism for the parent earthquake compatible with the geodynamic constraints in the region capable of reproducing most of the tsunami observations. The results of our study support the hypothesis that the 1761 event took place in the area of Coral Patch and Ampere seamounts, SW of the 1st November 1755, mega-earthquake source. Finally, this study shows the need to include the 1761 event in all seismic and tsunami hazard assessments in the Atlantic Ocean.

The prediction of tsunami travel time to Mataram City Indonesia based on North Lombok earthquake as the initial condition

The past earthquake records in North Lombok show the high level of earthquake hazard in this area. The maximum magnitude of the earthquake was 6.4 Mw on May 30th, 1979. But, there were no tsunami events records due to those earthquakes. Nevertheless, this area is very close to Mataram City (province capital city) and tourism area. Therefore, the assessment of tsunami hazard is very important. The tsunami simulation was conducted by using COMCOT Model, which is based on the North Lombok Earthquake as the initial condition. The simulation result shows the prediction of tsunami travel time is about 18 ~ 20 minutes from the source location to Mataram City. The height of the tsunami wave is 0.13 ~ 0.20 meters due to the earthquake magnitude is about 6 Mw.

Scenario-Based Tsunami Evacuation Analysis: A Case Study of Haimen Town, Taizhou, China

In current tsunami prevention and mitigation, evacuation is the most important method of saving people’s lives. Tsunami evacuation is analyzed for a given travel time and a specific inundation area. Before evacuation analysis, the tsunami inundation and tsunami travel time are first calculated by numerical modeling. This paper analyzes the tsunami evacuation of Haimen Town, Jiaojiang District, Taizhou City, China, under the hypothesis of a magnitude 9.0 earthquake scenario in the Ryukyu Trench. The Cornell multi-grid coupled tsunami (COMCOT) model and Tsunami Travel Time (TTT) model are used to calculate the tsunami inundation and tsunami travel time, respectively. GIS techniques are used to solve the evacuation problem. Both horizontal and vertical evacuations are adopted based on the Chinese community characteristics, disaster prevention facilities, land use, and other practical conditions. A cost raster is used to analyze the arrival cost of each grid in the study area. The location allocation and cost allocation methods are used to solve shelter selection and coverage problems, respectively. The network analyst is applied to provide evacuation routes for each community. The evacuation analysis results can provide a scientific reference for the development of tsunami evacuation plans.

An accessibility graph-based model to optimize tsunami evacuation sites and routes in Martinique, France

The risk of tsunami threatens the whole Caribbean coastline especially the Lesser Antilles. The first available models of tsunami propagation estimate that the travel time from the closest seismic sources would only take few minutes to impact the Martinique Island. Considering this threat, the most effective measure is a planned and organized evacuation of the coastal population. This requires an efficient regional warning system, estimation of the maximum expected tsunami flood height, preparation of the population to evacuate, and drawing up of local and regional emergency plans. In order to produce an efficient evacuation plan, we have to assess the number of people at risk, the potential evacuation routes, the safe areas and the available time to evacuate. However, this essential information is still lacking in the French West Indies emergency plans. This paper proposes a model of tsunami evacuation sites accessibility for Martinique directly addressed to decision makers. It is based on a population database at a local scale, the development of connected graphs of roads, the identification of potential safe areas and the velocity setting for pedestrians. Evacuation routes are calculated using the Dijkstra's algorithm which gives the shortest path between areas at risk and designated evacuation sites. The first results allow us to map the theoretical times and routes to keep the exposed population safe and to compare these results with a tsunami travel time scenario.

A wavefront orientation method for precise numerical determination of tsunami travel time

We present a highly accurate and computationally efficient method (herein, the "wavefront orientation method") for determining the travel time of oceanic tsunamis. Based on Huygens' Principle, the method uses an eight-point grid-point pattern and the most recent information on the orientation of the advancing wavefront to determine the time for a tsunami to travel to a specific oceanic location. The method is shown to provide improved accuracy and reduced anisotropy compared with the conventional multiple grid-point method presently in widespread use.

A wavefront orientation method for precise numerical determination of tsunami travel time

We present a highly accurate and computationally efficient method (herein, the "wavefront orientation method") for determining the travel time of oceanic tsunamis. Based on Huygens principle, the method uses an eight-point grid-point pattern and the most recent information on the orientation of the advancing wave front to determine the time for a tsunami to travel to a specific oceanic location. The method is shown to provide improved accuracy and reduced anisotropy compared with the conventional multiple grid-point method presently in widespread use.

THE 2010 CHILEAN AND THE 2011 TOHOKU TSUNAMI WAVES IMPACT TO RIVERS IN THE TOHOKU REGION, JAPAN

As a result when tsunami invades into river, it may not only a threat of damages to the banks but also cause the environmental problem such as inundation. Therefore, study of tsunami impacts to rivers becomes more important. The main objectives of this study are to investigate the tsunami wave propagation at different river morphologies based on real time measurements during the 2010 Chilean Tsunami and 2011 Tohoku Tsunami events. The aim is to learn empirically from the last extreme events tsunamis in order to suggest a better solution in terms of river and coastal management in the future. The analyzed results have been shown that the tsunami wave can be affected up to several tens kilometer upstream of a large river and the measured tsunami travel time inside the river is almost similar to the tsunami travel time calculated by using the long wave theory.