178 research outputs found
Tensile fracture along a bimaterial interface
Tensile fracture propagation along plane interface of isotropic media with different elastic propertie
Tsunami generation by dynamic displacement of sea bed due to dip-slip faulting
In classical tsunami-generation techniques, one neglects the dynamic sea bed
displacement resulting from fracturing of a seismic fault. The present study
takes into account these dynamic effects. Earth's crust is assumed to be a
Kelvin-Voigt material. The seismic source is assumed to be a dislocation in a
viscoelastic medium. The fluid motion is described by the classical nonlinear
shallow water equations (NSWE) with time-dependent bathymetry. The
viscoelastodynamic equations are solved by a finite-element method and the NSWE
by a finite-volume scheme. A comparison between static and dynamic
tsunami-generation approaches is performed. The results of the numerical
computations show differences between the two approaches and the dynamic
effects could explain the complicated shapes of tsunami wave trains.Comment: 16 pages, 10 figures, Accepted to Mathematics and Computers in
Simulation. Other author's papers can be downloaded at
http://www.cmla.ens-cachan.fr/~dutyk
On the contribution of the horizontal sea-bed displacements into the tsunami generation process
The main reason for the generation of tsunamis is the deformation of the
bottom of the ocean caused by an underwater earthquake. Usually, only the
vertical bottom motion is taken into account while the horizontal co-seismic
displacements are neglected in the absence of landslides. In the present study
we propose a methodology based on the well-known Okada solution to reconstruct
in more details all components of the bottom coseismic displacements. Then, the
sea-bed motion is coupled with a three-dimensional weakly nonlinear water wave
solver which allows us to simulate a tsunami wave generation. We pay special
attention to the evolution of kinetic and potential energies of the resulting
wave while the contribution of the horizontal displacements into wave energy
balance is also quantified. Such contribution of horizontal displacements to
the tsunami generation has not been discussed before, and it is different from
the existing approaches. The methods proposed in this study are illustrated on
the July 17, 2006 Java tsunami and some more recent events.Comment: 30 pages; 14 figures. Accepted to Ocean Modelling. Other authors
papers can be downloaded at http://www.lama.univ-savoie.fr/~dutykh
Influence of sedimentary layering on tsunami generation
The present article is devoted to the influence of sediment layers on the
process of tsunami generation. The main scope here is to demonstrate and
especially quantify the effect of sedimentation on vertical displacements of
the seabed due to an underwater earthquake. The fault is modelled as a
Volterra-type dislocation in an elastic half-space. The elastodynamics
equations are integrated with a finite element method. A comparison between two
cases is performed. The first one corresponds to the classical situation of an
elastic homogeneous and isotropic half-space, which is traditionally used for
the generation of tsunamis. The second test case takes into account the
presence of a sediment layer separating the oceanic column from the hard rock.
Some important differences are revealed. We conjecture that deformations in the
generation region may be amplified by sedimentary deposits, at least for some
parameter values. The mechanism of amplification is studied through careful
numerical simulations.Comment: 17 pages, 12 figures. Revised version for Computer Methods in Applied
Mechanics and Engineering. Other author's papers can be downloaded from
http://www.lama.univ-savoie.fr/~dutykh
An assessment of the tsunami risk in Muscat and Salalah, Oman, based on estimations of probable maximum loss
We present a method for determining an initial assessment of tsunami risk, with application for two coastal areas of Oman. Using open source GIS and seismic databases we carry out a tsunami risk assessment using a deterministic and probabilistic approach based on worst-case scenarios. A quick and effective method for estimating tsunami run-up without the use of complex modelling software is an important step in disaster risk reduction efforts as many government and emergency response organisations do not possess the expertise to carry out or interpret tsunami inundation numerical models. Estimates of probable maximum loss were calculated using a simple method of building identification and a revised building damage assessment technique. A series of tsunami risk maps were created for the coastal settlements of Muscat and Salalah, with the aim of improving tsunami response. We find Muscat to be at far greater risk of tsunami damage than Salalah; this is due in part to Muscat's proximity to potential tsunamigenic sources and the cities current level of urban infrastructure. Whilst much of the infrastructure in Salalah is currently at low risk from tsunami, development pressures could lead to increased risk within the region. It is hoped that the assessment of risk may go some way to a government led disaster risk reduction strategy being implemented in coastal Oman. The methods detailed provide a cheap and efficient means to quantify tsunami risk in many coastal Middle Eastern countries, of which several have poor disaster risk reduction strategies
Gravity changes from a stress evolution earthquake simulation of California
The gravity signal contains information regarding changes in density at all depths and
can be used as a proxy for the strain accumulation in fault networks. A stress evolution
time-dependent model was used to create simulated slip histories over the San Andreas
Fault network in California. Using a linear sum of the gravity signals from each fault
segment in the model, via coseismic gravity Green's functions, a time-dependent gravity
model was created. The steady state gravity from the long-term plate motion generates
a signal over 5 years with magnitudes of ±~2 μGal; the current limit of portable
instrument observations. Moderate to large events generate signal magnitudes in the
range of ~10 to ~80 μGal, well within the range of ground-based observations. The
complex fault network geometry of California significantly affects the spatial extent of the
gravity signal from the three events studied.Peer reviewe
Image Texture Characterization Using the Discrete Orthonormal S-Transform
We present a new efficient approach for characterizing image texture based on a recently published discrete, orthonormal space-frequency transform known as the DOST. We develop a frequency-domain implementation of the DOST in two dimensions for the case of dyadic frequency sampling. Then, we describe a rapid and efficient approach to obtain local spatial frequency information for an image and show that this information can be used to characterize the horizontal and vertical frequency patterns in synthetic images. Finally, we demonstrate that DOST components can be combined to obtain a rotationally invariant set of texture features that can accurately classify a series of texture patterns. The DOST provides the computational efficiency and multi-scale information of wavelet transforms, while providing texture features in terms of Fourier frequencies. It outperforms leading wavelet-based texture analysis methods
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