scholarly journals Landslide tsunamis in lakes

2015 ◽  
Vol 772 ◽  
pp. 784-804 ◽  
Author(s):  
Louis-Alexandre Couston ◽  
Chiang C. Mei ◽  
Mohammad-Reza Alam
Keyword(s):  
Near Field ◽  
Finite Size ◽  
Wave Runup ◽  
Multiple Reflections ◽  
Time Period ◽  
Near Shore ◽  
Lakes And Reservoirs ◽  
Landslide Tsunami ◽  
Tsunami Energy ◽  
Landslide Tsunamis

Landslides plunging into lakes and reservoirs can result in extreme wave runup at the shores. This phenomenon has claimed lives and caused damage to near-shore properties. Landslide tsunamis in lakes are different from typical earthquake tsunamis in the open ocean in that (i) the affected areas are usually within the near field of the source, (ii) the highest runup occurs within the time period of the geophysical event, and (iii) the enclosed geometry of a lake does not let the tsunami energy escape. To address the problem of transient landslide tsunami runup and to predict the resulting inundation, we utilize a nonlinear model equation in the Lagrangian frame of reference. The motivation for using such a scheme lies in the fact that the runup on an inclined boundary is directly and readily computed in the Lagrangian framework without the need to resort to approximations. In this work, we investigate the inundation patterns due to landslide tsunamis in a lake. We show by numerical computations that Airy’s approximation of an irrotational theory using Lagrangian coordinates can legitimately predict runup of large amplitude. We also demonstrate that in a lake of finite size the highest runup may be magnified by constructive interference between edge waves that are trapped along the shore and multiple reflections of outgoing waves from opposite shores, and may occur somewhat after the first inundation.

A waveform inversion technique for measuring elastic wave attenuation in cylindrical bars

Geophysics ◽  
1992 ◽  
Vol 57 (6) ◽  
pp. 854-859 ◽  
Author(s):  
Xiao Ming Tang
Keyword(s):  
Elastic Wave ◽  
Wave Attenuation ◽  
Waveform Inversion ◽  
Finite Size ◽  
Low Frequency ◽  
Frequency Range ◽  
Multiple Reflections ◽  
Low Frequencies ◽  
The Time Domain ◽  
Attenuation Values

A new technique for measuring elastic wave attenuation in the frequency range of 10–150 kHz consists of measuring low‐frequency waveforms using two cylindrical bars of the same material but of different lengths. The attenuation is obtained through two steps. In the first, the waveform measured within the shorter bar is propagated to the length of the longer bar, and the distortion of the waveform due to the dispersion effect of the cylindrical waveguide is compensated. The second step is the inversion for the attenuation or Q of the bar material by minimizing the difference between the waveform propagated from the shorter bar and the waveform measured within the longer bar. The waveform inversion is performed in the time domain, and the waveforms can be appropriately truncated to avoid multiple reflections due to the finite size of the (shorter) sample, allowing attenuation to be measured at long wavelengths or low frequencies. The frequency range in which this technique operates fills the gap between the resonant bar measurement (∼10 kHz) and ultrasonic measurement (∼100–1000 kHz). By using the technique, attenuation values in a PVC (a highly attenuative) material and in Sierra White granite were measured in the frequency range of 40–140 kHz. The obtained attenuation values for the two materials are found to be reliable and consistent.

ABSORPTION AND REFLECTION EXPERIMENTS ON HIGH-MOBILITY 2DEGs IN THE REGIME OF MICROWAVE-INDUCED RESISTANCE OSCILLATIONS

2004 ◽  
Vol 18 (27n29) ◽  
pp. 3481-3488 ◽  
Author(s):  
S. A. STUDENIKIN ◽  
M. POTEMSKI ◽  
A. S. SACHRAJDA ◽  
M. HILKE ◽  
L. N. PFEIFFER ◽  
...  
Keyword(s):  
Induced Resistance ◽  
Cyclotron Resonance ◽  
Broad Class ◽  
Near Field ◽  
Finite Size ◽  
High Mobility ◽  
Velocity Distribution Function ◽  
Resonant Absorption ◽  
Damping Factor ◽  
Oscillation Pattern

We have performed microwave absorption and near-field reflection experiments on a high mobility GaAs / AlGaAs heterostructure for the same conditions for which Microwave-Induced Resistance Oscillations (MIROs) are observed. It is shown that the electrodynamic aspect of the problem is important in these experiments. In the absorption experiments a broad CR line was observed due to a large reflection from the highly conductive electron gas. There were no additional features observed related to absorption at harmonics of the cyclotron resonance. In near-field reflection experiments a very different oscillation pattern was revealed when compared to MIROs. The oscillation pattern observed in the reflection experiments is probably due to plasma effects occurring in a finite-size sample. The whole microscopic picture of MIROs is more complicated than simply a resonant absorption at harmonics of the cyclotron resonance. Nevertheless, the experimental observations are in good agreement with the model by Durst et al. involving the photo-assisted scattering in the presence of a crossed magnetic field and dc bias. The observed damping factor of MIROs may be attributed to a change in the electron mobility as a function of temperature. MIROs may be considered as a light-induced drift effect, a broad class of phenomena associated with a light-induced asymmetry in the velocity distribution function.

A NOTE ON MULTIPLE REFLECTIONS

Geophysics ◽  
1949 ◽  
Vol 14 (3) ◽  
pp. 357-360
Author(s):  
G. E. Higgins
Keyword(s):  
Multiple Reflections ◽  
Geophysical Investigation ◽  
Seismic Prospecting ◽  
Reflection Seismic ◽  
Near Shore ◽  
Seismic Investigation

It was most interesting to read the January 1948 issue of Geophysics which was devoted to articles on multiple reflections and I would endorse the plea of Mr. Robert H. Mansfield for an issue of Geophysics to be devoted to the troublesome problems of offside energy in seismic prospecting. Trinidad has recently been the scene of intensive geophysical investigation, both gravimeter and reflection on seismic, and while neither method gives unambiguous answers to the local geologic problems, it is about the reflection seismic results which I should like to discuss. The first period of intensive seismic investigation in Trinidad was during 1938–1939 and certain anomalies observed then received further investigation during 1946–1947. During both periods of investigation, two particular phenomena were observed which may be called: 1. Near‐shore effect. 2. Coning.

scholarly journals The collective dynamics of self-propelled particles

2008 ◽  
Vol 595 ◽  
pp. 239-264 ◽  
Author(s):  
VISHWAJEET MEHANDIA ◽  
PRABHU R. NOTT
Keyword(s):  
Particle Concentration ◽  
Near Field ◽  
Continuous Process ◽  
Pair Correlation ◽  
Fluid Motion ◽  
Finite Size ◽  
Two Dimensions ◽  
Creeping Flow ◽  
Hydrodynamic Interactions ◽  
Dynamic Simulations

We propose a method for the dynamic simulation of a collection of self-propelled particles in a viscous Newtonian fluid. We restrict attention to particles whose size and velocity are small enough that the fluid motion is in the creeping flow regime. We propose a simple model for a self-propelled particle, and extended the Stokesian Dynamics method to conduct dynamic simulations of a collection of such particles. In our description, each particle is treated as a sphere with an orientation vector p, whose locomotion is driven by the action of a force dipole Sp of constant magnitude S0 at a point slightly displaced from its centre. To simplify the calculation, we place the dipole at the centre of the particle, and introduce a virtual propulsion force Fp to effect propulsion. The magnitude F0 of this force is proportional to S0. The directions of Sp and Fp are determined by p. In isolation, a self-propelled particle moves at a constant velocity u0p, with the speed u0 determined by S0. When it coexists with many such particles, its hydrodynamic interaction with the other particles alters its velocity and, more importantly, its orientation. As a result, the motion of the particle is chaotic. Our simulations are not restricted to low particle concentration, as we implement the full hydrodynamic interactions between the particles, but we restrict the motion of particles to two dimensions to reduce computation. We have studied the statistical properties of a suspension of self-propelled particles for a range of the particle concentration, quantified by the area fraction φa. We find several interesting features in the microstructure and statistics. We find that particles tend to swim in clusters wherein they are in close proximity. Consequently, incorporating the finite size of the particles and the near-field hydrodynamic interactions is of the essence. There is a continuous process of breakage and formation of the clusters. We find that the distributions of particle velocity at low and high φa are qualitatively different; it is close to the normal distribution at high φa, in agreement with experimental measurements. The motion of the particles is diffusive at long time, and the self-diffusivity decreases with increasing φa. The pair correlation function shows a large anisotropic build-up near contact, which decays rapidly with separation. There is also an anisotropic orientation correlation near contact, which decays more slowly with separation. Movies are available with the online version of the paper.

scholarly journals Error Estimation of Three Dipoles used as near Field sensors

2019 ◽  
Vol 8 (10) ◽  
pp. 1525-1529
Keyword(s):  
Error Estimation ◽  
Method Of Moments ◽  
Near Field ◽  
Ground Plane ◽  
Field Pattern ◽  
Multiple Reflections ◽  
Measuring Unit

Three sensors coupled in a crossed configuration are used as near field calculating unit of a transmitter in an unbounded ground plane. The Method of Moments is applied to calculate approximately the inaccuracy produced by the measuring unit in the near field. The Probe measures both copole, cross- pole and z-directed dipole components simultaneously. However, due to multiple reflections between the radiator and dipoles, near field values are changed. Computation was carried out for the calibration of the probe and to test the copole voltage and field (with no probe) in x-y plane at 10GHz to compare the relative tested co-pole voltage pattern with the relative tested field pattern (with no measuring unit). Since the relative tested co-pole voltage and field are analyzed, no inaccuracy is forced at the midpoint of the plane.

scholarly journals Near field diffraction of steel tape gratings illuminated with finite-size incoherent sources

Optik ◽  
2021 ◽  
pp. 168326
Author(s):  
Francisco Jose Torcal-Milla ◽  
Luis Miguel Sanchez-Brea
Keyword(s):  
Near Field ◽  
Finite Size

scholarly journals Spatial–temporal properties of afterslip associated with the 2015 Mw 8.3 Illapel earthquake, Chile

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Yunfei Xiang ◽  
Jianping Yue ◽  
Zhongshan Jiang ◽  
Yin Xing
Keyword(s):  
Early Stage ◽  
Near Field ◽  
Temporal Distribution ◽  
Slip Rate ◽  
Fault Slip ◽  
Coseismic Slip ◽  
Temporal Properties ◽  
Time Period ◽  
Illapel Earthquake ◽  
Postseismic Slip

AbstractIn order to characterize the spatial–temporal properties of postseismic slip motions associated with the 2015 Illapel earthquake, the daily position time series of 13 GNSS sites situated at the near-field region are utilized. Firstly, a scheme of postseismic signal extraction and modeling is introduced, which can effectively extract the postseismic signal with consideration of background tectonic movement. Based on the extracted postseismic signal, the spatial–temporal distribution of afterslip is inverted under the layered medium model. Compared with coseismic slip distribution, the afterslip is extended to both deep and two sides, and two peak slip patches are formed on the north and south sides. The afterslip is mainly cumulated at the depth of 10–50 km, and the maximum slip reaches 1.46 m, which is situated at latitude of − 30.50°, longitude of − 71.78°, and depth of 18.94 m. Moreover, the postseismic slip during the time period of 0–30 days after this earthquake is the largest, and the maximum of fault slip and corresponding slip rate reaches 0.62 m and 20.6 mm/day. Whereas, the maximum of fault slip rate during the time period of 180–365 days is only around 1 mm/day. The spatial–temporal evolution of postseismic slip motions suggests that large postseismic slip mainly occurs in the early stage after this earthquake, and the fault tend to be stable as time goes on. Meanwhile, the Coulomb stress change demonstrate that the postseismic slip motions after the Illapel earthquake may be triggered by the stress increase in the deep region induced by coseismic rupture.

scholarly journals Analysis of Mode Ⅲ Interface Fracture for Magneto-Electro-Elastic Materials

2018 ◽  
Vol 36 (6) ◽  
pp. 1209-1215
Author(s):  
Zhenhuan Zhou ◽  
Wang Xu ◽  
Zichen Deng ◽  
Xinsheng Xu ◽  
Chenghui Xu
Keyword(s):  
Near Field ◽  
Finite Size ◽  
Crack Tip ◽  
Interface Fracture ◽  
Far Field ◽  
Symplectic Method ◽  
Energy Release Rates ◽  
Small Set ◽  
Analytical Series ◽  
Regular Region

A novel finite element discretized symplectic method is developed for analyzing interface fracture of magneto-electro-elastic (MEE) materials under anti-plane loads. The overall cracked body is meshed by conventional finite elements and divided into a finite size singular region near the crack tip (near field) and a regular region far away from the crack tip (far field). In the near field, a based-Hamiltonian model is introduced to find the analytical series expressions, and the large number nodal unknowns are condensed into a small set of the undetermined coefficients of the symplectic series by a transformation. The nodal unknowns in the far field remain unchanged. The stress, electric and magnetic intensity factors, energy release rates (ERRs) and explicit expressions of singular field variables in the near field are simultaneously obtained without any processing.

scholarly journals LANDSLIDE-GENERATED TSUNAMIS: A NUMERICAL ANALYSIS OF THE NEAR-FIELD

2020 ◽  
pp. 8
Author(s):  
Alessandro Romano ◽  
Javier L. Lara ◽  
Gabriel Barajas ◽  
Benedetto Di Paolo ◽  
Giorgio Bellotti ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Numerical Study ◽  
Near Field ◽  
Experimental Tests ◽  
Wave Runup ◽  
Cfd Modelling ◽  
Tsunami Propagation ◽  
Tsunami Risk ◽  
Triggering Mechanisms ◽  
Landslide Triggering

There are coastal areas which are particularly prone to landslide-generated tsunami risk. The destructive effects caused by the impulsive waves, generated by landslide sources, can be strongly magnified by the characteristics of the so-called "confined geometries" (e.g. bays, reservoirs, lakes, volcanic islands, fjords, etc.). Complicated physical phenomena (e.g. trapping mechanisms, edge waves, wave runup, etc.) take place as a consequence of the interaction between the generated waves and the local bathymetry and control the tsunami propagation and interaction with the coast, often causing devastating consequences. Many past events of landslide-generated tsunamis testify this reality (e.g. Lituya Bay, Alaska, Fritz et al., 2009; Stromboli Island, Italy, Tinti et al., 2005; Anak Krakatau, Indonesia, Grilli et al., 2019). To reduce and mitigate the tsunami risk a proper comprehension, and modelling, of such complicated phenomena is crucial. Landslide-generated tsunamis have been largely studied by exploiting experimental, analytical and numerical modelling. Experimental tests are often time and money consuming, especially if 3D models are considered. Large facilities, as well as complicated experimental configurations and sophisticated measurement systems (e.g. Romano et al. 2016), are often needed. Furthermore, not always it is possible to explore in detail the influence of all the involved parameters, in particular those related to the landslide triggering mechanisms and rheology, that have a considerable influence on the wave characteristics in the so-called "near-field". To this end, numerical modelling can provide a valuable assistance. The new tools offered by the Computational Fluid Dynamics (CFD) methods represent a valuable means for shedding light on the unresolved aspects. In particular, the 3D CFD modelling techniques appear to be crucial as far as the tsunami characteristics in the near-field, induced by landslide sources, are concerned. Indeed, the accurate reproduction of the energy transfer between the landslide and the water is essential to model the tsunami generation and propagation mechanisms, allowing to explore a large variety of landslide triggering mechanisms and rheology. In this paper we present a numerical study of the landslide-generated tsunamis in the near-field.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/liUdiV2qXPg

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