Tsunami Earthquakes

Rapid estimation of tsunami earthquake magnitudes at local distance

Earth Planets and Space ◽

10.1186/s40623-021-01391-7 ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

Akio Katsumata ◽

Masayuki Tanaka ◽

Takahito Nishimiya

Keyword(s):

Magnitude Estimation ◽

Seismic Wave ◽

Seismic Waves ◽

Wave Amplitude ◽

Amplitude Distribution ◽

Distribution Method ◽

Finite Fault ◽

Tsunami Earthquakes ◽

Tsunami Earthquake ◽

The Moment

AbstractA tsunami earthquake is an earthquake event that generates abnormally high tsunami waves considering the amplitude of the seismic waves. These abnormally high waves relative to the seismic wave amplitude are related to the longer rupture duration of such earthquakes compared with typical events. Rapid magnitude estimation is essential for the timely issuance of effective tsunami warnings for tsunami earthquakes. For local events, event magnitude estimated from the observed displacement amplitudes of the seismic waves, which can be obtained before estimation of the seismic moment, is often used for the first tsunami warning. However, because the observed displacement amplitude is approximately proportional to the moment rate, conventional magnitudes of tsunami earthquakes estimated based on the seismic wave amplitude tend to underestimate the event size. To overcome this problem, we investigated several methods of magnitude estimation, including magnitudes based on long-period displacement, integrated displacement, and multiband amplitude distribution. We tested the methods using synthetic waveforms calculated from finite fault models of tsunami earthquakes. We found that methods based on observed amplitudes could not estimate magnitude properly, but the method based on the multiband amplitude distribution gave values close to the moment magnitude for many tsunami earthquakes. In this method, peak amplitudes of bandpass filtered waveforms are compared with those of synthetic records for an assumed source duration and fault mechanism. We applied the multiband amplitude distribution method to the records of events that occurred around the Japanese Islands and to those of tsunami earthquakes, and confirmed that this method could be used to estimate event magnitudes close to the moment magnitudes.

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Did the 2004 Sumatra-Andaman Earthquake Involve a Component of Tsunami Earthquakes?

Bulletin of the Seismological Society of America ◽

10.1785/0120050615 ◽

2007 ◽

Vol 97 (1A) ◽

pp. S296-S306 ◽

Cited By ~ 30

Author(s):

T. Seno ◽

K. Hirata

Keyword(s):

Tsunami Earthquakes ◽

Andaman Earthquake

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What Is Tsunami Earthquake?

10.1115/omae2021-63104 ◽

2021 ◽

Author(s):

Toshikazu Ebisuzaki

Keyword(s):

Surface Waves ◽

Seismic Waves ◽

Submarine Landslides ◽

Lower Efficiency ◽

Tsunami Waves ◽

Tsunami Earthquakes ◽

Seismic Surface Waves ◽

Tsunami Earthquake ◽

Volcanic Islands ◽

2004 Tsunami

Abstract A tsunami earthquake is defined as an earthquake which induces abnormally strong tsunami waves compared with its seismic magnitude (Kanamori 1972; Kanamori and Anderson 1975; Tanioka and Seno 2001). We investigate the possibility that the surface waves (Rayleigh, Love, and tsunami waves) in tsunami earthquakes are amplified by secondly submarine landslides, induced by the liquefaction of the sea floor due to the strong vibrations of the earthquakes. As pointed by Kanamori (2004), tsunami earthquakes are significantly stronger in longer waves than 100 s and low in radiation efficiencies of seismic waves by one or two order of magnitudes. These natures are in favor of a significant contribution of landslides. The landslides can generate seismic waves with longer period with lower efficiency than the tectonic fault motions (Kanamori et al 1980; Eissler and Kanamori 1987; Hasegawa and Kanamori 1987). We further investigate the distribution of the tsunami earthquakes and found that most of their epicenters are located at the steep slopes in the landward side of the trenches or around volcanic islands, where the soft sediments layers from the landmass are nearly critical against slope failures. This distribution suggests that the secondly landslides may contribute to the tsunami earthquakes. In the present paper, we will investigate the rapture processes determined by the inversion analysis of seismic surface waves of tsunami earthquakes can be explained by massive landslides, simultaneously triggered by earthquakes in the tsunami earthquakes which took place near the trenches.

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EQUILIBRIUM OF ECOLOGY AND ENGLISH CHALLENGES FOR TOMORROW’S LEADERS: A STUDY

Kongunadu Research Journal ◽

10.26524/krj162 ◽

2017 ◽

Vol 4 (1) ◽

pp. 5-7

Author(s):

Chinnadurai T ◽

Nagaraj P

Keyword(s):

Childhood Obesity ◽

Transfer Students ◽

Ecological System ◽

Environmental Action ◽

English Teacher ◽

Air Conditioner ◽

Next Generation ◽

Language Classroom ◽

Tsunami Earthquakes ◽

Better Than

The vision of the greenish world refashions lightning into brownish ground. When our human minds enlarge, our souls and hearts become brownie and narrow. Our world is expected to face massive calamities which have already given enough signs to be aware of disasters like Tsunami, earthquakes, global warmingand less prime span of living. According to the poet W.H. Auden “a culture is no better than its woods”.Today’s children are being taught how to cut away the trees and build fine air conditioner rooms. Being an English teacher, one has the greatest responsibility in language classroom in molding the future leaders. If we do not care of our square classroom today, our circle globe will be no more for next generation. Only our four pillars of classroom are to shape our Earth. Students are facing many problems in indoor learning like attention difficulties, diminished use of sense, hyperactivity, and childhood obesity and disconnection from real things. English teacher has to have the efficiency to transfer students’ ability into positive environmental action to preserve our earth as over grown living areas. It’s our responsibility to grow our children with greenish perspective. This paper focuses how to develop our ecological system through English fortomorrow’s leaders.

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The Role of Frontal Thrusts in Tsunami Earthquake Generation

Bulletin of the Seismological Society of America ◽

10.1785/0120210154 ◽

2021 ◽

Author(s):

Raquel P. Felix ◽

Judith A. Hubbard ◽

James D. P. Moore ◽

Adam D. Switzer

Keyword(s):

Subduction Zones ◽

Generation Process ◽

Lower Amplitude ◽

Tsunami Earthquakes ◽

Fault Bend ◽

Wave Heights ◽

Seafloor Deformation ◽

Tsunami Earthquake ◽

Tsunami Energy ◽

The Impact

ABSTRACT The frontal sections of subduction zones are the source of a poorly understood hazard: “tsunami earthquakes,” which generate larger-than-expected tsunamis given their seismic shaking. Slip on frontal thrusts is considered to be the cause of increased wave heights in these earthquakes, but the impact of this mechanism has thus far not been quantified. Here, we explore how frontal thrust slip can contribute to tsunami wave generation by modeling the resulting seafloor deformation using fault-bend folding theory. We then quantify wave heights in 2D and expected tsunami energies in 3D for both thrust splays (using fault-bend folding) and down-dip décollement ruptures (modeled as elastic). We present an analytical solution for the damping effect of the water column and show that, because the narrow band of seafloor uplift produced by frontal thrust slip is damped, initial tsunami heights and resulting energies are relatively low. Although the geometry of the thrust can modify seafloor deformation, water damping reduces these differences; tsunami energy is generally insensitive to thrust ramp parameters, such as fault dip, geological evolution, sedimentation, and erosion. Tsunami energy depends primarily on three features: décollement depth below the seafloor, water depth, and coseismic slip. Because frontal ruptures of subduction zones include slip on both the frontal thrust and the down-dip décollement, we compare their tsunami energies. We find that thrust ramps generate significantly lower energies than the paired slip on the décollement. Using a case study of the 25 October 2010 Mw 7.8 Mentawai tsunami earthquake, we show that although slip on the décollement and frontal thrust together can generate the required tsunami energy, <10% was contributed by the frontal thrust. Overall, our results demonstrate that the wider, lower amplitude uplift produced by décollement slip must play a dominant role in the tsunami generation process for tsunami earthquakes.

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