Analysis of the tsunami amplification effect by resonance in Yeongil Bay

Predicting tsunami hazards based on the tsunami source, propagation, runup patterns is critical to protect humans and property. Potential tsunami zone, as well as the historical tsunamis in 1983 and 1993, can be a threat to the east coast of South Korea. The Korea Meteorological Administration established a tsunami forecast warning system to reduce damage from tsunamis, but it does not consider tsunami amplification in the bay due to resonance. In this study, the Numerical model, Cornell Multi-grid Coupled Tsunami model, was used to investigate natural frequency in the bay due to coastal geometry. The study area is Yeongill bay in Pohang, southeast of South Korea, because this area is a natural bay and includes three harbors where resonance significantly occurs. This study generated a Gaussian-shaped tsunami, propagated it into the Yeongill bay, and compared numerical modeling results with data from tide gauge located in Yeongill bay during several storms through spectral analysis. It was found that both energies of tsunamis and storms were amplified at the same frequencies, and maximum tsunami wave height was amplified about 3.12 times. The results in this study can contribute to quantifying the amplification of tsunami heights in the bay.

Nonlinear Model of Coastal Flooding by a Highly Turbulent Tsunami

When a tsunami wave comes from ocean and propagates through the shelf, it is very important to predict several dangerous factors: (a) maximum flooding of the coast, (b) tsunami wave height on the coast, (c) velocity of the tsunami front propagation through the coast, and (d) time of tsunami arriving at a given point in the coast and around it. In this study we study the separate case where the angle of inclination α of the seacoast is equal to zero. A linear solution of this problem is unsatisfactory since it gives an infinite rate of the coastal inundation that means the coast is flooded instantly and without a frontal boundary. In this study, we propose a principally new exact analytical solution of this problem based on nonlinear theory for the reliable recognizing these essential tsunami characteristics. The obtained formulas indicate that the tsunami wave can be stopped (or very strongly eliminated) in the shelf zone until approaching the shoreline. For this aim, it is necessary to artificially raising several dozens of bottom protrusions to the level of the calm water.

KAJIAN DAERAH RENDAMAN TSUNAMI DI PESISIR TELUK LAMPUNG AKIBAT PERUBAHAN TOPOGRAFI GUNUNG ANAK KRAKATAU DI TAHUN 2018

The eruption of the Anak Krakatoa volcano (GAK) in December 2018 caused part of the body of GAK to collapse into the sea and caused a tsunami. This avalanche also caused changes in the topography of GAK. If there is a repeat of the disaster with the current GAK topography, it will certainly cause changes in tsunami wave height at the shoreline which will affect changes in the tsunami inundation area. Because the location of the Lampung Bay coastal area which is quite close to GAK makes the Lampung Bay coastal area vulnerable to the tsunami disaster. So, it is necessary to study the tsunami inundation area due to changes in the current GAK topography in the coastal area of Lampung Bay. This study was conducted using non-numerical methods to obtain wave heights at the shoreline and the Berryman methods to obtain tsunami inundation areas in the coastal areas of Lampung bay by making three scenarios. Based on the results of the study, it is known that the height of tsunami waves, which are 13 meters, 26 meters, and 39 meters with an average time of arrival of tsunami waves on the shoreline is 57 minutes. Where there are seven sub-districts submerged by the tsunami with a distance of about 160 meters to 1.6 kilometers.

Parametric Catastrophe Bonds for Tsunamis: CAT-in-a-Box Trigger and Intensity-Based Index Trigger Methods

This study presents a calibration of CAT-in-a-Box and intensity-based index trigger mechanisms for parametric tsunami catastrophe bonds. Trigger conditions for the former are based on fundamental event characteristics, such as earthquake location and magnitude, whereas those for the latter utilize tsunami wave height measurements at a series of observation stations. These solutions are illustrated for a building portfolio in Iwanuma City in Miyagi Prefecture, Japan, by considering a new seafloor observation network S-net off the Tohoku-Hokkaido coast of Japan. Performances of the two types of parametric solutions are quantitatively evaluated and compared with each other to discuss their advantages and disadvantages.

Projection of Tsunami Wave Height at East-Coast of Peninsular Malaysia using Green’s Law

In recent years, studies regarding a new source of tsunami-genic earthquake at South China Sea region known as Manila Trench earthquake have attracted the attention of many researchers. It is expected that this subduction zone is capable to trigger large moment magnitude earthquake and affects countries located within South China Sea. The objective of this study is to project tsunami wave height and arrival time generated from Manila Trench earthquake towards coastal areas located along east-coast of Peninsular Malaysia. This study focuses on simulating tsunami at four different moment magnitudes by using TUNA-M2 model to record wave height and arrival time at the offshore areas. Then the Green’s law is used to approximate reliable tsunami wave height when approaching onshore. Results obtained in this study showed that tsunami waves from Manila Trench are estimated to arrive at coastal areas of east-coast Peninsular Malaysia between 9.1 to 10.25 hours post-earthquake occurrence. The observation points located at offshore of Kelantan are anticipated to experience the highest wave height as compared to other observation points located at offshore areas of Terengganu and Pahang. This study is important to the coastal communities as it provides vital information on possible tsunami occurrences in the future.