scholarly journals Envelope synthesis of short-period seismograms in 3-D random media for a point shear dislocation source based on the forward scattering approximation: Application to small strike-slip earthquakes in southwestern Japan

2011 ◽  
Vol 116 (B8) ◽  
Author(s):  
Kaoru Sawazaki ◽  
Haruo Sato ◽  
Takeshi Nishimura
Keyword(s):  
Random Media ◽  
Strike Slip ◽  
Forward Scattering ◽  
Dislocation Source ◽  
Scattering Approximation ◽  
Short Period

Aftershocks and surface faulting associated with the intraplate Guinea, West Africa, earthquake of 22 December 1983

1987 ◽  
Vol 77 (5) ◽  
pp. 1579-1601
Author(s):  
C. J. Langer ◽  
M. G. Bonilla ◽  
G. A. Bollinger
Keyword(s):  
West Africa ◽  
Focal Mechanism ◽  
Main Shock ◽  
Strike Slip ◽  
Fault System ◽  
Epicentral Area ◽  
Lateral Strike Slip ◽  
Focal Mechanism Solutions ◽  
Short Period ◽  
East West

Abstract This study reports on the results of geological and seismological field studies conducted following the rare occurrence of a moderate-sized West African earthquake (mb = 6.4) with associated ground breakage. The epicentral area of the northwestern Guinea earthquake of 22 December 1983 is a coastal margin, intraplate locale with a very low level of historical seismicity. The principal results include the observation that seismic faulting occurred on a preexisting fault system and that there is good agreement among the surface faulting, the spatial distribution of the aftershock hypocenters, and the composite focal mechanism solutions. We are not able, however, to shed any light on the reason(s) for the unexpected occurrence of this intraplate earthquake. Thus, the significance of this study is its contribution to the observational datum for such earthquakes and for the seismicity of West Africa. The main shock was associated with at least 9 km of surface fault-rupture. Trending east-southeast to east-west, measured fault displacements up to ∼13 cm were predominantly right-lateral strike slip and were accompanied by an additional component (5 to 7 cm) of vertical movement, southwest side down. The surface faulting occurred on a preexisting fault whose field characteristics suggest a low slip rate with very infrequent earthquakes. There were extensive rockfalls and minor liquefaction effects at distances less than 10 km from the surface faulting and main shock epicenter. Main shock focal mechanism solutions derived from teleseismic data by other workers show a strong component of normal faulting motion that was not observed in the ground ruptures. A 15-day period of aftershock monitoring, commencing 22 days after the main shock, was conducted. Eleven portable, analog short-period vertical seismographs were deployed in a network with an aperture of 25 km and an average station spacing of 7 km. Ninety-five aftershocks were located from the more than 200 recorded events with duration magnitudes of about 1.5 or greater. Analysis of a selected subset (91) of those events define a tabular aftershock volume (26 km long by 14 km wide by 4 km thick) trending east-southeast and dipping steeply (∼60°) to the south-southwest. Composite focal mechanisms for groups of events, distributed throughout the aftershock volume, exhibit right-lateral, strike-slip motion on subvertical planes that strike almost due east. Although the general agreement between the field geologic and seismologic results is good, our preferred interpretation is for three en-echelon faults striking almost due east-west.

Study of the tsunami source in the Palu Bay following the Mw7.5 2018 Sulawesi earthquake

2020 ◽  
Author(s):  
Fabrizio Romano ◽  
Haider Hasan ◽  
Stefano Lorito ◽  
Finn Løvholt ◽  
Beatriz Brizuela ◽  
...  
Keyword(s):  
Tide Gauge ◽  
Joint Inversion ◽  
Seismic Source ◽  
Strike Slip ◽  
Tsunami Source ◽  
Fault System ◽  
Tsunami Propagation ◽  
Slip Mechanism ◽  
Short Period ◽  
Nonlinear Joint

<p>On 28 September 2018 a Mw 7.5 strike-slip earthquake occurred on the Palu-Koro fault system in the Sulawesi Island. Immediately after the earthquake a powerful tsunami hit the Palu Bay causing large damages and numerous fatalities.</p><p>Several works, inverting seismic or geodetic data, clearly estimated the slip distribution of this event, but the causative source of the tsunami is still not completely understood; indeed, the strike-slip mechanism of the seismic source alone might not be sufficient to explain the large runups observed (> 6 m) along the coast of the Palu Bay, and thus one or more additional non-seismic sources like a landslide could have contributed to generate the big tsunami. An insight of that can be found in an extraordinary collection of amateur videos, and on the only available tide gauge in the Bay, at Pantoloan, that showed evidence for a short period wave of at least 2-3 minutes, compatible with a landslide.</p><p>In this study, we attempt to discriminate the contribution in the tsunami generation of both the seismic source and  some supposed landslides distributed along the coast of the Bay.</p><p>In particular, we attempt to estimate the causative source of the tsunami by means of a nonlinear joint inversion of geodetic (InSAR) and runup data. We use a fault geometry consistent with the Sentinel-2 optical analysis results and analytically compute the geodetic Green’s functions. The same fault model is used to compute the initial condition for the seismic tsunami Green’s functions, including the contribution of the horizontal deformation due to the gradient of the bathymetry (10 m spatial resolution); the landslide tsunami Green’s functions are computed the software BingClaw by placing several hypothetical sources in the Bay. In both the cases the tsunami propagation is modelled by numerically solving the nonlinear shallow water equations.</p><p>In this work we also attempt to address the validity of Green’s functions approach (linearity) for earthquake and landslide sources as well as the wave amplitude offshore as predictor of nearby runup.</p>

Forward scattering on short period GaAs/AlAs superlattices

1990 ◽  
Vol 228 (1-3) ◽  
pp. 151-155 ◽  
Author(s):  
Bernard Jusserand ◽  
Francis Mollot ◽  
Daniel Paquet
Keyword(s):  
Forward Scattering ◽  
Short Period

scholarly journals Characteristic Length and Time Scales of the Highly Forward Scattering of Photons in Random Media

2019 ◽  
Vol 10 (1) ◽  
pp. 93 ◽  
Author(s):  
Hiroyuki Fujii ◽  
Moegi Ueno ◽  
Kazumichi Kobayashi ◽  
Masao Watanabe
Keyword(s):  
Radiative Transfer ◽  
Time Scales ◽  
Analytical Solutions ◽  
Random Media ◽  
Three Dimensional ◽  
Forward Scattering ◽  
Diffusion Equations ◽  
Transport Models ◽  
Photon Diffusion ◽  
Photon Transport

Background: Elucidation of the highly forward scattering of photons in random media such as biological tissue is crucial for further developments of optical imaging using photon transport models. We evaluated length and time scales of the photon scattering in three-dimensional media. Methods: We employed analytical solutions of the time-dependent radiative transfer, M-th order delta-Eddington, and photon diffusion equations (RTE, dEM, and PDE). We calculated the fluence rates at different source-detector distances and optical properties. Results: We found that the zeroth order dEM and PDE, which approximate the highly forward scattering to the isotropic scattering, are valid in longer length and time scales than approximately 10 / μ t ′ and 40 / μ t ′ v , respectively, where μ t ′ is the reduced transport coefficient and v the speed of light in a medium. The first and second order dEM, which approximate the highly forward-peaked phase function by the first two and three Legendre moments, are valid in the longer scales than approximately 4.0 / μ t ′ and 6.3 / μ t ′ v ; 2.8 / μ t ′ and 3.5 / μ t ′ v , respectively. The boundary conditions less influence the length scales, while they reduce the times scales from those for bulk at the longer length scale than approximately 4.0 / μ t ′ . Conclusion: Our findings are useful for constructions of accurate and efficient photon transport models. We evaluated length and time scales of the highly forward scattering of photons in various kinds of three-dimensional random media by analytical solutions of the radiative transfer, M-th order delta-Eddington, and photon diffusion equations.

scholarly journals Forward scattering approximation and bosonization in integer quantum Hall systems

2008 ◽  
Vol 323 (3) ◽  
pp. 673-704
Author(s):  
M. Rosenau da Costa ◽  
H. Westfahl ◽  
A.O. Caldeira
Keyword(s):  
Quantum Hall ◽  
Forward Scattering ◽  
Quantum Hall Systems ◽  
Scattering Approximation ◽  
Integer Quantum

Singularities in forward scattering through random media

1991 ◽  
Vol 1 (2) ◽  
pp. 195-206 ◽  
Author(s):  
P J Roberts ◽  
J B Pendry
Keyword(s):  
Random Media ◽  
Forward Scattering
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