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 Rapid estimation of tsunami earthquake magnitudes at local distance

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.

What Is Tsunami Earthquake?

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.

scholarly journals Fault model of the 2012 doublet earthquake, near the up-dip end of the 2011 Tohoku-Oki earthquake, based on a near-field tsunami: implications for intraplate stress state

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Tatsuya Kubota ◽  
Ryota Hino ◽  
Daisuke Inazu ◽  
Syuichi Suzuki
Keyword(s):  
Stress State ◽  
Frictional Coefficient ◽  
Fault Model ◽  
Japan Trench ◽  
Time Interval ◽  
Depth Range ◽  
Seismic Zone ◽  
Bending Stress ◽  
Normal Faulting ◽  
Brittle Strength

AbstractOn December 7, 2012, an earthquake occurred within the Pacific Plate near the Japan Trench, which was composed of deep reverse- and shallow normal-faulting subevents (Mw 7.2 and 7.1, respectively) with a time interval of ~10 s. It had been known that the stress state within the plate was characterized by shallow tensile and deep horizontal compressional stresses due to the bending of the plate (bending stress). This study estimates the fault model of the doublet earthquake utilizing tsunami, teleseismic, and aftershock data and discusses the stress state within the incoming plate and spatiotemporal changes seen in it after the 2011 Tohoku-Oki earthquake. We obtained the vertical extents of the fault planes of deep and shallow subevents as ~45–70 km and ~5 (the seafloor)–35 km, respectively. The down-dip edge of the shallow normal-faulting seismic zone (~30–35 km) deepened significantly compared to what it was in 2007 (~25 km). However, a quantitative comparison of the brittle strength and bending stress suggested that the change in stress after the Tohoku-Oki earthquake was too small to deepen the down-dip end of the seismicity by ~10 km. To explain the seismicity that occurred at a depth of ~30–35 km, the frictional coefficient in the normal-faulting depth range required would have had to be ~0.07 ≤ μ ≤ ~0.2, which is significantly smaller than the typical friction coefficient. This suggests the infiltration of pore fluid along the bending faults, down to ~30–35 km. It is considered that the plate had already yielded to a depth of ~35 km before 2011 and that the seismicity of the area was reactivated by the increase in stress from the Tohoku-Oki earthquake.

Investigation of the best coseismic fault model of the 2006 Java tsunami earthquake based on mechanisms of postseismic deformation

2016 ◽  
Vol 117 ◽  
pp. 64-72 ◽  
Author(s):  
Endra Gunawan ◽  
Irwan Meilano ◽  
Hasanuddin Z. Abidin ◽  
Nuraini Rahma Hanifa ◽  
Susilo
Keyword(s):  
Fault Model ◽  
Postseismic Deformation ◽  
Tsunami Earthquake

scholarly journals Hypocenter relocations and tsunami simulation for the 15 November 2014 Northern Molucca Sea earthquake in Indonesia

2017 ◽  
Vol 15 (3) ◽  
pp. 1 ◽  
Author(s):  
Aditya Riadi Gusman ◽  
Andri D. Nugraha ◽  
Hasbi Ash Shiddiqi
Keyword(s):  
Fault Model ◽  
Double Difference ◽  
Reverse Fault ◽  
Depth Range ◽  
Tide Gauges ◽  
K Value ◽  
Tsunami Waves ◽  
Tsunami Observations ◽  
Length Width ◽  
Tomography Method

A reverse fault earthquake (Mw 7.1) occurred in the Northern Molucca Sea, Indonesia, on 15 November 2014 at 2:31:40 UTC. The earthquake produced small tsunami waves that are recorded at Jailolo (9 cm), Tobelo (1 cm), and Menado (3 cm) tide gauges. The Indonesian Agency for Climatology, Meteorology, and Geophysics (BMKG) issued a timely (5 minutes after the earthquake) tsunami warning for the event. We used the teleseismic double‐difference seismic tomography method (teletomoDD) to relocate the hypocenters of the mainshock and the aftershocks. The relocated hypocenter of the mainshock for the 2014 Northern Molucca Sea earthquake is located at 1.923°N, 126.539°E, and depth of 48.87 km. In general, the relocated aftershock hypocenters are shallower than those from the BMKG catalog. The relocated hypocenters are distributed within a depth range of 6 to 64 km. The aftershock area from the relocated hypocenters is 80 km long and 55 km wide. The estimated seismic moment from the Global CMT solution (GCMT) was 4.75 × 1019 Nm. We simulated the tsunami from fault model of each GCMT nodal plane to find a fault model that can best explain the observed tsunami heights at Jailolo, Tobelo, and Menado tide gauges. The best single fault model for this event is dipping to the west, has fault length, width, and slip amount of 47 km, 25 km, and 1.16 m, respectively. The K value calculated using the observed and simulated tsunami heights for this best model is 1.026,  suggests a very good fit to tsunami observations.

 The source characteristics and tsunami resonance effect of the 2020 Samos earthquake in Eastern Aegean

2021 ◽  
Author(s):  
Gui Hu ◽  
Wanpeng Feng ◽  
Yuchen Wang ◽  
Linlin Li ◽  
Xiaohui He ◽  
...  
Keyword(s):  
Normal Fault ◽  
Coastal Areas ◽  
Wave Period ◽  
Tsunami Source ◽  
Tide Gauges ◽  
Tsunami Waves ◽  
Source Characteristics ◽  
The North ◽  
Eastern Aegean ◽  
Tsunami Waveforms

<p>On October 30 2020 11:51 UTC, a Mw 6.9 normal fault earthquake occurred off the northern coasts of Samos Island, Eastern Aegean, Greece. Over a 120 people were killed and more than 1000 people were injured during the seismic sequence. The quake produced a moderate tsunami that swapped the coastal areas of Izmir (Turkey) and Samos (Greece) with inundation heights up to ~3 m. Finding the source of such a tsunami has been puzzling as a normal fault earthquake with Mw 6.9 would not be considered significant enough to generate metric-scale waves. Furthermore, the lack of near-field observations has made the identification of the seismogenic fault responsible for the mainshock difficult. In this study, we infer the source characteristics from multiple observation data, including InSAR, GPS, teleseismic waves and tsunami waves. We first  generate two Sentinel-1 co-seismic interferograms with a maximum Line of Sight (LOS) change of 8 cm on the coastal areas at the Samos island. We obtain a north-dipping fault model, which can slightly better explain the geodetic observations and teleseismic P waves. To understand the potential tsunami source, we use several earthquake slip models collected from different research groups to conduct tsunami simulations.  Comparing simulated tsunami waveforms with those measured at 6 local tide gauges, we show that the north-dipping fault can fit tsunami records better than the south-dipping fault. The north-dipping fault hypothesis is also further supported by the spatial distributions of the aftershocks. The spectral analysis of tsunami waveforms at selected tide gauges suggests that the tsunami period band is within 4.6 ~ 21.3 min and the primary wave period is ~14.2 min. Using this wave period as an indirect constraint, we show that the source dimension of our slip model can produce tsunami waveforms with similar wave period. We also find high-energy wave of the Samos earthquake that lasted 20 h, and fundamental oscillation periods of Sığacık Bay are remarkably close to some dominating tsunami periods. We infer the coseismic seafloor displacement alone is not enough to create disastrous effects on coastal cities; therefore we suggest that the tsunami waves may have been amplified by local coastline and tsunami resonance with local bay, or another source, e.g. triggered landslides.</p>

Tsunami earthquake can occur elsewhere along the Japan Trench-Historical and geological evidence for the 1677 earthquake and tsunami

2016 ◽  
Vol 121 (5) ◽  
pp. 3504-3516 ◽  
Author(s):  
H. Yanagisawa ◽  
K. Goto ◽  
D. Sugawara ◽  
K. Kanamaru ◽  
N. Iwamoto ◽  
...  
Keyword(s):  
Japan Trench ◽  
Geological Evidence ◽  
Tsunami Earthquake

scholarly journals Long Tsunami Oscillations Following the 30 October 2020 Mw 7.0 Aegean Sea Earthquake: Observations and Modelling

2021 ◽  
Author(s):  
Mohammad Heidarzadeh ◽  
Ignatius Ryan Pranantyo ◽  
Ryo Okuwaki ◽  
Gozde Guney Dogan ◽  
Ahmet C. Yalciner
Keyword(s):  
Eastern Mediterranean ◽  
Aegean Sea ◽  
Fault Model ◽  
Tsunami Source ◽  
Tide Gauges ◽  
Arrival Times ◽  
The North ◽  
Tsunami Observations ◽  
Level Data ◽  
Run Up

AbstractEastern Mediterranean Sea has experienced four tsunamigenic earthquakes since 2017, which delivered moderate damage to coastal communities in Turkey and Greece. The most recent of these tsunamis occurred on 30 October 2020 in the Aegean Sea, which was generated by an Mw 7.0 normal-faulting earthquake, offshore Izmir province (Turkey) and Samos Island (Greece). The earthquake was destructive and caused death tolls of 117 and 2 in Turkey and Greece, respectively. The tsunami produced moderate damage and killed one person in Turkey. Due to the semi-enclosed nature of the Aegean Sea basin, any tsunami perturbation in this sea is expected to trigger several basin oscillations. Here, we study the 2020 tsunami through sea level data analysis and numerical simulations with the aim of further understanding tsunami behavior in the Aegean Sea. Analysis of data from available tide gauges showed that the maximum zero-to-crest tsunami amplitude was 5.1–11.9 cm. The arrival times of the maximum tsunami wave were up to 14.9 h after the first tsunami arrivals at each station. The duration of tsunami oscillation was from 19.6 h to > 90 h at various tide gauges. Spectral analysis revealed several peak periods for the tsunami; we identified the tsunami source periods as 14.2–23.3 min. We attributed other peak periods (4.5 min, 5.7 min, 6.9 min, 7.8 min, 9.9 min, 10.2 min and 32.0 min) to non-source phenomena such as basin and sub-basin oscillations. By comparing surveyed run-up and coastal heights with simulated ones, we noticed the north-dipping fault model better reproduces the tsunami observations as compared to the south-dipping fault model. However, we are unable to choose a fault model because the surveyed run-up data are very limited and are sparsely distributed. Additional researches on this event using other types of geophysical data are required to determine the actual fault plane of the earthquake.

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