Large submarine landslides in the Japan Trench: A new scenario for additional tsunami generation

2012 ◽  
Vol 39 (5) ◽  
pp. n/a-n/a ◽  
Author(s):  
Kiichiro Kawamura ◽  
Tomoyuki Sasaki ◽  
Toshiya Kanamatsu ◽  
Arito Sakaguchi ◽  
Yujiro Ogawa
Keyword(s):  
Japan Trench ◽  
Submarine Landslides ◽  
Tsunami Generation

Seismic strengthening of diatom-rich sediments: A comparison of slope sediments from Chilean lakes and the Japan Trench margin

2020 ◽  
Author(s):  
Jasper Moernaut ◽  
Gauvain Wiemer ◽  
Ting-Wei Wu ◽  
Ariana Molenaar ◽  
Achim Kopf ◽  
...  
Keyword(s):  
Shear Strength ◽  
Sediment Cores ◽  
Hollow Structure ◽  
Japan Trench ◽  
Submarine Landslides ◽  
Compression Tests ◽  
Seismic Strengthening ◽  
Active Margins ◽  
Clayey Silt

<p>Earthquakes are a main trigger of subaqueous landslides and surficial sediment remobilization at ocean margins and lake basins. If the earthquake loading is insufficient to lead to sediment failure, the subsequent dewatering and inherent compaction may enhance the shear strength of sedimentary slopes, a process termed „seismic strengthening“, which is believed to be especially relevant for the upper 10s of meters. This mechanism has been suggested to explain the observed paucity of submarine landslides on active margins when compared to the short recurrence of strong earthquakes in such settings. However, only few field studies were dedicated on this topic and little is known about which settings are especially prone to seismic strengthening.</p><p>Here, we present geotechnical data from diatom-rich sedimentary slopes in Chilean lakes and at the Japan Trench margin. We use the overburden-normalized undrained shear strength as an indicator of consolidation state. In Chile, this data is derived from in-situ dynamic cone penetrometer measurements, whereas the Japan data is obtained by lab vane shear tests on sediment cores. Both settings show extremely elevated shear strength of about ~5-10 times higher than expected for normally-consolidated sediment in the upper meters of a sequence. Significant overconsolidation is confirmed by one-dimensional compression tests, providing overconsolidation ratios of ~2-8 (Chilean lakes) and 4-9 (Japan Trench). For each setting, the shear strength profiles of sites with different sedimentation rates show very similar trends when they are normalized over the sediment age instead of over overburden stress. As older sediments experienced more earthquakes, this apparent age-dependency may form a new argument supporting the hypothesis of seismic strengthening. Following previous lab experiments on mixtures of diatoms and clayey-silt, we postulate that a high susceptibility to seismic strengthening in both settings is caused by the abundance of diatom frustules which are typically characterized by a high particle interlocking and surface roughness. On the Japan Trench margin, biogenic opal forms ~15% in dry weight, and given the hollow structure of diatom frustules, we infer that diatoms take up a considerable space in the in-situ sediment texture. We conclude that seismically active margins with diatom-rich sediments have a reduced susceptibility to submarine landslide hazards.</p>

scholarly journals Owen Ridge deep-water submarine landslides: implications for tsunami hazard along the Oman coast

2013 ◽  
Vol 13 (2) ◽  
pp. 417-424 ◽  
Author(s):  
M. Rodriguez ◽  
N. Chamot-Rooke ◽  
H. Hébert ◽  
M. Fournier ◽  
P. Huchon
Keyword(s):  
Finite Difference ◽  
Arabian Sea ◽  
Tsunami Hazard ◽  
Potential Hazard ◽  
Submarine Landslides ◽  
Tsunami Generation ◽  
Difference Model ◽  
Tsunami Waves ◽  
Wave Elevation ◽  
Sediment Failure

Abstract. The recent discovery of voluminous submarine landslides along the Owen Ridge may represent a source of tsunami hazard for the nearby Oman coast. We assess the severity of this potential hazard by performing numerical simulations of tsunami generation and propagation from the biggest landslide (40 km3 in volume) observed along the Owen Ridge. A finite-difference model, assimilating the landslide to a visco-plastic flow, simulates tsunami generation. Computation results show that Salalah city (190 000 inhabitants) is impacted by 2.5 m-high tsunami waves one hour after sediment failure. Higher wave elevation values (4 m) are reached in the low populated Sawqara Bay over 80 min after slide initiation. Although large submarine failures along remote oceanic ridges are infrequent, this study reveals an underestimated source of tsunami hazard in the Arabian Sea.

scholarly journals Detailed analysis of tsunami waveforms generated by the 1946 Aleutian tsunami earthquake

2001 ◽  
Vol 1 (4) ◽  
pp. 171-175 ◽  
Author(s):  
Y. Tanioka ◽  
T. Seno
Keyword(s):  
Seismic Moment ◽  
Seismic Waves ◽  
Boussinesq Equation ◽  
Fault Model ◽  
Japan Trench ◽  
Tsunami Generation ◽  
Tide Gauges ◽  
Tsunami Waveforms ◽  
Tsunami Earthquake ◽  
20 Nm

Abstract. The 1946 Aleutian earthquake was a typical tsunami earthquake which generated abnormally larger tsunami than expected from its seismic waves. Previously, Johnson and Satake (1997) estimated the fault model of this earthquake using the tsunami waveforms observed at tide gauges. However, they did not model the second pulse of the tsunami at Honolulu although that was much larger than the first pulse. In this paper, we numerically computed the tsunami waveforms using the linear Boussinesq equation to determine the fault model which explains the observed tsunami waveforms including the large second pulse observed at Honolulu. The estimated fault width is 40–60 km which is much narrower than the fault widths of the typical great underthrust earthquakes, the 1957 Aleutian and the 1964 Alasuka earthquakes. A previous study of the 1896 Sanriku earthquake, another typical tsunami earthquake, suggested that the additional uplift of the sediments near the Japan Trench had a large effect on the tsunami generation. In this study, we also show that the additional uplift of the sediments near the trench, due to a large coseismic horizon-tal movement of the backstop, had a significant effect on the tsunami generation of the 1946 Aleutian earthquake. The estimated seismic moment of the 1946 Aleutian earthquake is 17–19 × 1020 20 Nm (Mw 8.1).

scholarly journals A NUMERICAL MODEL FOR THE EFFICIENT SIMULATION OF MULTIPLE LANDSLIDE-TSUNAMI SCENARIOS

2020 ◽  
pp. 20
Author(s):  
Verdiana Iorio ◽  
Giorgio Bellotti ◽  
Claudia Cecioni ◽  
Stephan Grilli
Keyword(s):  
Numerical Model ◽  
Probabilistic Approach ◽  
Coastal Communities ◽  
Submarine Landslides ◽  
Tsunami Generation ◽  
Linear Superposition ◽  
Efficient Simulation ◽  
Landslide Tsunami ◽  
Tsunami Scenarios ◽  
Accurate Computations

Submarine landslides can pose serious tsunami hazard to coastal communities, occurring frequently near the coast itself. The properties of the tsunami and the consequent inundation depend on many factors, such as the geometry, the rheology and the kinematic of the landslide and the local bathymetry. However, when evaluating the risk related to landslide tsunamis, it is very difficult to accurately predict all of the above mentioned parameters. It is therefore useful to carry out many simulations of tsunami generation and propagation, with reference to different landslide scenarios, in order to deal with such uncertainties (see for example the probabilistic approach by Grilli et al. 2009). Accurate computations of landslide tsunami generation, propagation, and inundation, however, is computationally expensive, thus limiting the possible maximum number of scenarios. To partially overcome this difficulty, in the present research, a numerical model is proposed that can efficiently compute a large number of tsunami simulations triggered by different landslides. The main goal is to provide a numerical tool that can be used in a Monte Carlo approach framework. Following the study by Ward (2001), we propose a methodology taking advantage of the linear superposition of elementary tsunami solutions.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/uYOvdsutmBw

scholarly journals Anatomy of strike-slip fault tsunami genesis

2021 ◽  
Vol 118 (19) ◽  
pp. e2025632118
Author(s):  
Ahmed Elbanna ◽  
Mohamed Abdelmeguid ◽  
Xiao Ma ◽  
Faisal Amlani ◽  
Harsha S. Bhat ◽  
...  
Keyword(s):  
Ground Motions ◽  
Three Dimensional ◽  
Coastal Areas ◽  
Strike Slip ◽  
Submarine Landslides ◽  
Tsunami Generation ◽  
Dynamic Rupture ◽  
Rupture Dynamics ◽  
Earthquake Rupture Dynamics ◽  
Tsunami Model

Tsunami generation from earthquake-induced seafloor deformations has long been recognized as a major hazard to coastal areas. Strike-slip faulting has generally been considered insufficient for triggering large tsunamis, except through the generation of submarine landslides. Herein, we demonstrate that ground motions due to strike-slip earthquakes can contribute to the generation of large tsunamis (>1 m), under rather generic conditions. To this end, we developed a computational framework that integrates models for earthquake rupture dynamics with models of tsunami generation and propagation. The three-dimensional time-dependent vertical and horizontal ground motions from spontaneous dynamic rupture models are used to drive boundary motions in the tsunami model. Our results suggest that supershear ruptures propagating along strike-slip faults, traversing narrow and shallow bays, are prime candidates for tsunami generation. We show that dynamic focusing and the large horizontal displacements, characteristic of strike-slip earthquakes on long faults, are critical drivers for the tsunami hazard. These findings point to intrinsic mechanisms for sizable tsunami generation by strike-slip faulting, which do not require complex seismic sources, landslides, or complicated bathymetry. Furthermore, our model identifies three distinct phases in the tsunamic motion, an instantaneous dynamic phase, a lagging coseismic phase, and a postseismic phase, each of which may affect coastal areas differently. We conclude that near-source tsunami hazards and risk from strike-slip faulting need to be re-evaluated.

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