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Asymptotic Expansion and Perturbation
Published in K.T. Chau, Theory of Differential Equations in Engineering and Mechanics, 2017
We now consider a scenario for a large submarine earthquake and apply the shallow wave approximation to calculate the wave speed of a tsunami wave. When a large shallow submarine earthquake of magnitude 7.5 or higher occurs in deep sea (on the order of 8000 m), large sea bottom movements occurs. Water will be displaced upward or downward, and a so-called tsunami (literally means harbor wave in Japanese) will be generated. Because the size of the rupture surface for a large destructive earthquake is on the order of 200 km or more, the wavelength of such an initial disturbance is also on the order of 200 km. Using these data, (12.507) shows that the period of such an initial wave form is in the order of 12 minutes. In addition, we have hlL ≈ 0.04 such that the shallow water wave assumption is valid.
Tsunami hazard analysis for Chinese coast from potential earthquakes in the western North Pacific
Published in Geomatics, Natural Hazards and Risk, 2020
Jingming Hou, Ye Yuan, Tao Li, Zhiyuan Ren
The tsunami threat to China in the western North Pacific is mainly from the Circum-Pacific seismic belt, which is one of the three major seismic belts in the world. The northwestern part of this seismic belt stretches from the Aleutian Islands, the Kamchatka Peninsula, the Kuril Islands, the Japanese Archipelago to Taiwan and Philippines, and also includes the line from Japan to the Mariana Islands. In this region, the Pacific plate, the Philippine Sea plate and the Eurasian plate interact with each other, often causing earthquakes (Zang and Ning 1996). When an submarine earthquake occurs, the massive movement of the Earth crust causes the water to rise, and then the seawater is pulled back under the effect of gravity, thus generating a tsunami.
Physical modeling of tsunamis generated by subaerial, partially submerged, and submarine landslides
Published in Coastal Engineering Journal, 2020
Tomoyuki Takabatake, Martin Mäll, Dawn Chenxi Han, Naoto Inagaki, Daichi Kisizaki, Miguel Esteban, Tomoya Shibayama
A tsunami can be generated not only by a submarine earthquake but also by a landslide, amongst other generation mechanisms. Based on the relative position of the landslide and the water surface, landslide-generated tsunamis can be classified into three types: subaerial, partially submerged, and submarine. Historically, there are records of all these types of landslides having generated a tsunami that caused catastrophic damage to human lives and properties. For instance, a subaerial landslide that took place at Vajont Dam in Italy in 1963 generated a significant wave, and eventually caused around 2,000 fatalities to a village downstream (Panizzo et al. 2005a; Genevois and Ghirotti 2005). The largest recorded tsunami run-up of 524 m was also produced by a subaerial landslide at Lituya Bay, Alaska in 1958 (Miller 1960; Fritz, Hager, and Minor 2001). Recently, the tsunamis generated by the flank collapse of Anak Krakatau volcano, located in the middle of Sunda Strait, devastated coastal communities in Java and Sumatra Island, Indonesia in 2018 (Takabatake et al. 2019). The 1988 Papua New Guinea earthquake generated a significant tsunami that resulted in over 15 m of run-up at Sissano split, causing over 2,200 fatalities, and is believed to have been amplified by a submarine landslide (Tappin et al. 2001; Tappin, Watts, and Grilli 2008). In the 2010 Haiti Earthquake, land along roughly 400 m coastline collapsed into the sea as a result of the earthquake, generating tsunami waves of up to 3 m in height (Fritz et al. 2013). All types of landslide-generated tsunamis could have occurred during the 2018 Palu Earthquake, in Sulawesi Island, Indonesia. Frederik et al. (2019) and Aranguiz et al. (2020) conducted bathymetric survey and identified several slide scarps and submarine slide deposits. Sassa and Takagawa (2019), Takagi et al. (2019), and Omira et al. (2019) indicated that extensive land area disappeared and could have generated significant tsunamis. A scarp at a cliff was also identified by Arikawa et al. (2018) as the origin of a potential subaerial landslide tsunami to the north of Palu Bay. As a result of these landslides, significant tsunami waves causing inundation of up to 5 m devastated the City of Palu and the Donggala Regency, resulting in around 4,000 fatalities (Mikami et al. 2019; Stolle et al. 2020; Harnantyari et al. 2020).