Tsunami Efficiency Due to Very Slow Earthquakes

2021 ◽  
Author(s):  
Sebastián Riquelme ◽  
Mauricio Fuentes
Keyword(s):  
Numerical Modeling ◽  
Earthquake Rupture ◽  
Rupture Propagation ◽  
Rupture Velocity ◽  
Quasistatic Problem ◽  
Megathrust Earthquakes ◽  
Slow Earthquakes ◽  
Static Part ◽  
Tsunami Amplitude ◽  
Large Earthquakes

Abstract Often, tsunami “sources” have been treated as a quasistatic problem. Initial studies have demonstrated that, for earthquake rupture velocities in the span of 1.5–3  km/s, the kinematic and static part of the tsunami can be treated separately. However, very slow earthquake rupture velocities in the span of 0.1–1  km/s have not been included in tsunami analytical or numerical modeling. Here, we calculated the tsunami efficiency, extending Kajiura’s definition for different models. We demonstrated that rupture velocity cannot be neglected for very slow events, that is, rupture velocities slower than 0.5  km/s. We also examined the relation of magnitude, earthquake rupture velocity, and tsunami amplitude to the efficiency of very slow tsunamigenic earthquakes. Hypothetical megathrust earthquakes (Mw>8.5) with very slow rupture velocities amplify energy from 10 to 60 times larger than moderate to large earthquakes (7.0<Mw<8.5) in the direction of rupture propagation.

TSUNAMI AMPLIFICATION ALONG THE EASTERN COAST OF INDIA AND SRI LANKA DUE TO EARTHQUAKE RUPTURE PROPAGATION IN THE SUMATRA-NICOBAR-ANDAMAN TRENCHES

2009 ◽  
Vol 03 (02) ◽  
pp. 67-75 ◽  
Author(s):  
KENJI HIRATA
Keyword(s):  
Sri Lanka ◽  
Numerical Simulations ◽  
General Feature ◽  
Tsunami Source ◽  
Eastern Coast ◽  
Earthquake Rupture ◽  
Rupture Propagation ◽  
Rupture Velocity ◽  
Slow Earthquakes ◽  
Tsunami Amplitude

We investigated an effect of earthquake rupture propagation, or tsunami source propagation, on offshore tsunami amplitude through numerical simulations. In the numerical simulations, we used satellite-based real bathymetry and a realistic fault configuration for M9 class great earthquakes, and we allowed an earthquake rupture to propagate one-dimensionally in the long-axis direction of the fault. Various earthquake rupture velocities as well as various fault lengths were tested. A general feature is that the slower the earthquake rupture velocity, the larger the tsunami amplitude. This suggests that the effect of earthquake rupture propagation cannot be neglected for most of tsunamis generated by slow earthquakes. Along the eastern coast of India and Sri Lanka, however, earthquake rupture propagation makes tsunami amplification behaviors complicated and varied from station to station. This is because amplification of offshore tsunami is controlled by source configuration and bathymetry as well as rupture velocity.

A comparison of two methods for earthquake source inversion using strong motion seismograms

1994 ◽  
Vol 37 (6) ◽  
Author(s):  
B. P. Cohee ◽  
G. C. Beroza
Keyword(s):  
Rise Time ◽  
Seismic Moment ◽  
Strong Motion ◽  
Rupture Time ◽  
Rupture Propagation ◽  
Rupture Velocity ◽  
Strong Motion Data ◽  
Motion Data ◽  
Inversion Methods ◽  
Window Method

In this paper we compare two time-domain inversion methods that have been widely applied to the problem of modeling earthquake rupture using strong-motion seismograms. In the multi-window method, each point on the fault is allowed to rupture multiple times. This allows flexibility in the rupture time and hence the rupture velocity. Variations in the slip-velocity function are accommodated by variations in the slip amplitude in each time-window. The single-window method assumes that each point on the fault ruptures only once, when the rupture front passes. Variations in slip amplitude are allowed and variations in rupture velocity are accommodated by allowing the rupture time to vary. Because the multi-window method allows greater flexibility, it has the potential to describe a wider range of faulting behavior; however, with this increased flexibility comes an increase in the degrees of freedom and the solutions are comparatively less stable. We demonstrate this effect using synthetic data for a test model of the Mw 7.3 1992 Landers, California earthquake, and then apply both inversion methods to the actual recordings. The two approaches yield similar fits to the strong-motion data with different seismic moments indicating that the moment is not well constrained by strong-motion data alone. The slip amplitude distribution is similar using either approach, but important differences exist in the rupture propagation models. The single-window method does a better job of recovering the true seismic moment and the average rupture velocity. The multi-window method is preferable when rise time is strongly variable, but tends to overestimate the seismic moment. Both methods work well when the rise time is constant or short compared to the periods modeled. Neither approach can recover the temporal details of rupture propagation unless the distribution of slip amplitude is constrained by independent data.

scholarly journals Numerical modeling of seismic waves by discontinuous spectral element methods

2018 ◽  
Vol 61 ◽  
pp. 1-37 ◽  
Author(s):  
Paola F. Antonietti ◽  
Alberto Ferroni ◽  
Ilario Mazzieri ◽  
Roberto Paolucci ◽  
Alfio Quarteroni ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Discontinuous Galerkin ◽  
Large Scale ◽  
Seismic Waves ◽  
Spectral Element ◽  
Fully Discrete ◽  
Time Marching ◽  
Space Discretization ◽  
Large Earthquakes

We present a comprehensive review of Discontinuous Galerkin Spectral Element (DGSE) methods on hybrid hexahedral/tetrahedral grids for the numerical modeling of the ground motion induced by large earthquakes. DGSE methods combine the exibility of discontinuous Galerkin meth-ods to patch together, through a domain decomposition paradigm, Spectral Element blocks where high-order polynomials are used for the space discretization. This approach allows local adaptivity on discretization parameters, thus improving the quality of the solution without affecting the compu-tational costs. The theoretical properties of the semidiscrete formulation are also revised, including well-posedness, stability and error estimates. A discussion on the dissipation, dispersion and stability properties of the fully-discrete (in space and time) formulation is also presented. Here space dis-cretization is obtained based on employing the leap-frog time marching scheme. The capabilities of the present approach are demonstrated through a set of computations of realistic earthquake scenar-ios obtained using the code SPEED (http://speed.mox.polimi.it), an open-source code specifically designed for the numerical modeling of large-scale seismic events jointly developed at Politecnico di Milano by The Laboratory for Modeling and Scientific Computing MOX and by the Department of Civil and Environmental Engineering.

Multicycle Simulation of Strike-Slip Earthquake Rupture for Use in Near-Source Ground-Motion Simulations

2021 ◽  
Author(s):  
Percy Galvez ◽  
Anatoly Petukhin ◽  
Paul Somerville ◽  
Jean-Paul Ampuero ◽  
Ken Miyakoshi ◽  
...  
Keyword(s):  
Ground Motion ◽  
Stress Drop ◽  
Slip Rate ◽  
Rupture Process ◽  
Earthquake Rupture ◽  
Rupture Velocity ◽  
Source Inversion ◽  
Dynamic Rupture ◽  
Wide Range ◽  
Source Scaling

ABSTRACT Realistic dynamic rupture modeling validated by observed earthquakes is necessary for estimating parameters that are poorly resolved by seismic source inversion, such as stress drop, rupture velocity, and slip rate function. Source inversions using forward dynamic modeling are increasingly used to obtain earthquake rupture models. In this study, to generate a large number of physically self-consistent rupture models, rupture process of which is consistent with the spatiotemporal heterogeneity of stress produced by previous earthquakes on the same fault, we use multicycle simulations under the rate and state (RS) friction law. We adopt a one-way coupling from multicycle simulations to dynamic rupture simulations; the quasidynamic solver QDYN is used to nucleate the seismic events and the spectral element dynamic solver SPECFEM3D to resolve their rupture process. To simulate realistic seismicity, with a wide range of magnitudes and irregular recurrence, several realizations of 2D-correlated heterogeneous random distributions of characteristic weakening distance (Dc) in RS friction are tested. Other important parameters are the normal stress, which controls the stress drop and rupture velocity during an earthquake, and the maximum value of Dc, which controls rupture velocity but not stress drop. We perform a parametric study on a vertical planar fault and generate a set of a hundred spontaneous rupture models in a wide magnitude range (Mw 5.5–7.4). We validate the rupture models by comparison of source scaling, ground motion (GM), and surface slip properties to observations. We compare the source-scaling relations between rupture area, average slip, and seismic moment of the modeled events with empirical ones derived from source inversions. Near-fault GMs are computed from the source models. Their peak ground velocities and peak ground accelerations agree well with the ground-motion prediction equation values. We also obtain good agreement of the surface fault displacements with observed values.

Physics of Earthquake Rupture Propagation

2018 ◽  
Vol 733 ◽  
pp. 1-3
Author(s):  
Shiqing Xu ◽  
Eiichi Fukuyama ◽  
Amir Sagy ◽  
Mai-Linh Doan
Keyword(s):  
Earthquake Rupture ◽  
Rupture Propagation

The Chile subduction zone : Nature of the lithosphere between alternating regions of slow earthquakes versus non slow earthquakes

2020 ◽  
Author(s):  
Pousali Mukherjee ◽  
Yoshihiro Ito ◽  
Emmanuel S. Garcia ◽  
Raymundo Plata-Martinez ◽  
Takuo Shibutani
Keyword(s):  
Subduction Zones ◽  
Receiver Function ◽  
Function Analysis ◽  
Fluid Distribution ◽  
Inversion Method ◽  
Megathrust Earthquakes ◽  
Slow Earthquake ◽  
Slow Earthquakes ◽  
Receiver Function Analysis ◽  
Earthquake Area

<p>Subduction zones host some of the greatest megathrust earthquakes in the world. Slow earthquakes have been discovered around the subduction zones of the Pacific rim very close to megathrust earthquakes. Investigating the lithosphere of the slow earthquake area versus non slow-earthquake area in subduction zones is crucial in understanding the role of the internal structure to control slow earthquakes. In this study, we investigate the lithospheric structure of stations in the slow earthquake area and non slow-earthquake areas in Chile using receiver function analysis and inversion method using teleseismic earthquakes. Here we focus on, especially the Vp/Vs ratios from both slow and non-slow earthquake areas, because the Vp/Vs ratio is sensitive to the fluid distribution in the lithosphere; the fluid distribution possibly controls the potential occurrence of slow earthquakes. Additionally, the nature of the slab can also play a crucial factor. The Vp/Vs ratio results across depth shows significantly higher value in the deeper oceanic slab region beneath the stations in the slow earthquake areas with higher contrast at the boundary.</p>

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