Seismic surface waves from Amchitka Island Test Site Events and their relation to source mechanism

1973 ◽  
Vol 78 (14) ◽  
pp. 2467-2474 ◽  
Author(s):  
David von Seggern
Keyword(s):  
Surface Waves ◽  
Test Site ◽  
Source Mechanism ◽  
Seismic Surface Waves

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.

Evidence of metamaterial physics at the geophysics scale: the METAFORET experiment

2019 ◽  
Author(s):  
Martin Lott ◽  
Philippe Roux ◽  
Stéphane Garambois ◽  
Philippe Guéguen ◽  
Andrea Colombi
Keyword(s):  
Surface Waves ◽  
Attenuation Length ◽  
Dense Forest ◽  
Complex Wave ◽  
Seismic Surface Waves ◽  
Source Excitation ◽  
Ground Penetrating ◽  
Dense Seismic Array ◽  
Seismic Wavefield ◽  
Large Frequency

Abstract The METAFORET experiment was designed to demonstrate that complex wave physics phenomena classically observed at the meso- and micro-scales in acoustics and in optics also apply at the geophysics scale. In particular, the experiment shows that a dense forest of trees can behave as a locally resonant metamaterial for seismic surface waves. The dense arrangement of trees anchored into the ground creates anomalous dispersion curves for surface waves, which highlight a large frequency band-gap around one resonant frequency of the trees, at ∼45 Hz. This demonstration is carried out through the deployment of a dense seismic array of ∼1000 autonomous geophones providing seismic recordings under vibrating source excitation at the transition between an open field and a forest. Additional geophysical equipment was deployed (e.g. ground-penetrating radar, velocimeters on trees) to provide essential complementary measurements. Insights and interpretations on the observed seismic wavefield, including the attenuation length, the intensity ratio between the field and the forest and the surface wave polarization, are validated with 2D numerical simulations of trees over a layered halfspace.

Shear-coupled higher mode seismic surface waves

1967 ◽  
Vol 57 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Stuart Crampin
Keyword(s):  
Surface Waves ◽  
Wave Motion ◽  
S Wave ◽  
Higher Modes ◽  
Mode Wave ◽  
Mode Dispersion ◽  
Seismic Surface Waves ◽  
Wave Trains ◽  
Group Velocities

abstract Some higher mode wave trains with irregular dispersion, and some anomalies in the S-wave motion at epicentral distances less than 30°, are shown to be shear-coupled higher modes. The group velocities along the higher mode portions of the paths agree well with observations of direct higher mode dispersion in Scandinavia.

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