Rupture Process of 6 April 2009 L'Aquila, Italy,Mw6.3 Earthquake: a Comparison Between Apparent Source Time Function Method and Direct Wave Inversion Method

2010 ◽  
Vol 53 (3) ◽  
pp. 473-484
Author(s):  
Yong ZHANG ◽  
Yun-Tai CHEN ◽  
Li-Sheng XU
Keyword(s):  
Function Method ◽  
Rupture Process ◽  
Time Function ◽  
Inversion Method ◽  
Source Time Function ◽  
Direct Wave ◽  
Wave Inversion ◽  
Apparent Source

THE RUPTURE PROCESS OF THE 2004 SUMATRA-ANDAMAN EARTHQUAKE VIEWED FROM STRAINMETER DATA

2009 ◽  
Vol 03 (01) ◽  
pp. 35-42
Author(s):  
YASUHIRO YOSHIDA
Keyword(s):  
Rupture Process ◽  
Earthquake Source ◽  
Time Function ◽  
Rupture Propagation ◽  
Source Time Function ◽  
Total Moment ◽  
Giant Earthquake ◽  
Back Azimuth ◽  
Andaman Earthquake ◽  
Tsunami Warnings

Methods for estimating source time function (STF) and temporal variation of back-azimuth of the earthquake source using volmetric and multi-components strainmeter installed in Japan were developed. By applying those methods to the 2004 Sumatra-Andaman giant earthquake, the STF was estimated using volmetric strain records. The duration was about 700 s and the total moment was 5.2 × 1022 Nm, which were almost consistent with other results using seismometer records. Back-azimuth was successfully estimated by multi-components strain records, but the rupture propagation effect was not observed. Those methods were good tools for rapid estimation of giant earthquake source process and were useful for tsunami warnings.

Interferometry by deconvolution: Part 1 — Theory for acoustic waves and numerical examples

Geophysics ◽  
2008 ◽  
Vol 73 (3) ◽  
pp. S115-S128 ◽  
Author(s):  
Ivan Vasconcelos ◽  
Roel Snieder
Keyword(s):  
Boundary Condition ◽  
Acoustic Waves ◽  
Time Function ◽  
Source Time Function ◽  
Field Quantity ◽  
Representation Theorems ◽  
Direct Wave ◽  
Wavefield Separation ◽  
Acoustic Media ◽  
Deconvolution Interferometry

Interferometry allows for synthesis of data recorded at any two receivers into waves that propagate between these receivers as if one of them behaves as a source. This is accomplished typically by crosscorrelations. Based on perturbation theory and representation theorems, we show that interferometry also can be done by deconvolutions for arbitrary media and multidimensional experiments. This is important for interferometry applications in which (1) excitation is a complicated source-time function and/or (2) when wavefield separation methods are used along with interferometry to retrieve specific arrivals. Unlike using crosscorrelations, this method yields only causal scattered waves that propagate between the receivers. We offer a physical interpretation of deconvolution interferometry based on scattering theory. Here we show that deconvolution interferometry in acoustic media imposes an extra boundary condition, which we refer to as the free-point or clamped-point boundary condition, depending on the measured field quantity. This boundary condition generates so-called free-point scattering interactions, which are described in detail. The extra boundary condition and its associated artifacts can be circumvented by separating the reference waves from scattered wavefields prior to interferometry. Three wavefield-separation methods that can be used in interferometry are direct-wave interferometry, dual-field interferometry, and shot-domain separation. Each has different objectives and requirements.

On the use of simulated annealing method and cross-validation theory for deconvolution of seismograms

1996 ◽  
Vol 86 (4) ◽  
pp. 1187-1193 ◽  
Author(s):  
F. Courboulex ◽  
J. Virieux ◽  
D. Gibert
Keyword(s):  
Simulated Annealing ◽  
Water Level ◽  
Cross Validation ◽  
Ad Hoc ◽  
Time Function ◽  
Source Time Function ◽  
Simulated Annealing Method ◽  
Propagation Effects ◽  
Apparent Source ◽  
Annealing Method

Abstract In order to retrieve the apparent source time function (ASTF) seen at a given station, one must take into account propagation effects, site, and instrumental influences. Removing these effects can be performed by a deconvolution of the mainshock seismogram by a seismogram of a smaller event recorded at the same station. This smaller event must occur nearby the mainshock, and the associated seismogram is considered as an empirical Green's function. We propose a deconvolution based on the simulated annealing method, and we compare it with the often-used spectral division technique. We show on both synthetic and real signals that the simulated annealing deconvolution (SAD) provides stable and positive ASTF, whereas results from spectral division are very sensitive to an ad hoc parameter called water level. Finally, the application of cross-validation analysis between the three components of the seismogram in addition to the (SAD allows us to estimate errors on the ASTF.

scholarly journals Fully probabilistic seismic source inversion – Part 1: Efficient parameterisation

2013 ◽  
Vol 5 (2) ◽  
pp. 1125-1162 ◽  
Author(s):  
S. C. Stähler ◽  
K. Sigloch
Keyword(s):  
Moment Tensor ◽  
Source Parameters ◽  
Practical Importance ◽  
Principal Component ◽  
Seismic Source ◽  
Empirical Orthogonal Functions ◽  
Time Function ◽  
Source Inversion ◽  
Source Time Function ◽  
Earthquake Parameters

Abstract. Seismic source inversion is a non-linear problem in seismology where not just the earthquake parameters themselves, but also estimates of their uncertainties are of great practical importance. Probabilistic source inversion (Bayesian inference) is very adapted to this challenge, provided that the parameter space can be chosen small enough to make Bayesian sampling computationally feasible. We propose a framework for PRobabilistic Inference of Source Mechanisms (PRISM) that parameterises and samples earthquake depth, moment tensor, and source time function efficiently by using information from previous non-Bayesian inversions. The source time function is expressed as a weighted sum of a small number of empirical orthogonal functions, which were derived from a catalogue of >1000 STFs by a principal component analysis. We use a likelihood model based on the cross-correlation misfit between observed and predicted waveforms. The resulting ensemble of solutions provides full uncertainty and covariance information for the source parameters, and permits to propagate these source uncertainties into travel time estimates used for seismic tomography. The computational effort is such that routine, global estimation of earthquake mechanisms and source time functions from teleseismic broadband waveforms is feasible.

scholarly journals Analysis of Tsunami Inundation due in Pangandaran Tsunami Earthquake in South Java Area Based on Finite Faults Solutions Model

2020 ◽  
Vol 10 (2) ◽  
pp. 114
Author(s):  
Ramadhan Priadi ◽  
Dede Yunus ◽  
Berlian Yonanda ◽  
Relly Margiono
Keyword(s):  
Fault Plane ◽  
Body Wave ◽  
Scaling Law ◽  
Source Mechanism ◽  
Inversion Method ◽  
Tsunami Modeling ◽  
Residential Areas ◽  
North West ◽  
Wave Inversion ◽  
Run Up

On July 17, 2006 an earthquake with a magnitude of  7.7 triggered a tsunami that struck 500 km of the coast in the south of the island of Java. The tsunami generated is classified as an earthquake tsunami because the waves generated were quite large compared to the strength of the earthquake. The difference in the strength of the earthquake and the resulting tsunami requires a tsunami modeling study with an estimated fault area in addition to using aftershock and scaling law. The purpose of this study is to validate tsunamis that occur based on the estimation of the source mechanism and the area of earthquake faults. Determination of earthquake source mechanism parameters using the Teleseismic Body-Wave Inversion method that uses teleseismic waveforms with the distance recorded waveform from the source between  Whereas, tsunami modeling is carried out using the Community Model Interface for Tsunami (commit) method. Fault plane parameters that obtained were strike , dip , and rake  with dominant slip pointing up to north-north-west with a maximum value of 1.7 m. The fault plane is estimated to have a length of 280 km in the strike direction and a width of 102 km in the dip direction. From the results of the tsunami modeling, the maximum inundation area is 0.32 km2 in residential areas flanked by Pangandaran bays and the maximum run-up of 380.96 cm in Pasir Putih beach area. The tsunami modeling results in much smaller inundation and run-up from field observations, it was assumed that the fault plane segmentation had occurred due to the greater energy released than the one from the fault area, causing waves much larger than the modeling results.

The 14 September 1995 (M = 7.3) Copala, Mexico, earthquake: A source study using teleseismic, regional, and local data

1997 ◽  
Vol 87 (4) ◽  
pp. 999-1010
Author(s):  
F. Courboulex ◽  
M. A. Santoyo ◽  
J. F. Pacheco ◽  
S. K. Singh
Keyword(s):  
Time Window ◽  
Time Function ◽  
Source Process ◽  
Source Time Function ◽  
Nonlinear Method ◽  
Local Data ◽  
Plate Interface ◽  
Linear Inversion ◽  
Field Source ◽  
Mexico Earthquake

Abstract We analyze source characteristics of the 14 September 1995, Copala, Mexico, earthquake (M = 7.3) using teleseismic, regional, and local seismograms. In the analysis of the teleseismic and the regional seismic waves, we apply the empirical Green's function (EGF) technique. The recording of an appropriate aftershock is taken as the EGF and is used to deconvolve the mainshock seismogram, thus obtaining an apparent far-field source-time function at each station. The deconvolution has been done using surface waves. For teleseismic data, we apply a spectral deconvolution method that enables us to obtain 37 apparent source-time functions (ASTFs) at 29 stations. In the analysis of the regional broadband seismograms, we use two different aftershocks as EGF, and the deconvolution is performed in the time domain with a nonlinear method, imposing a positivity constraint, and the best azimuth for the directivity vector is obtained through a grid-search approach. We also analyze two near-source accelerograms. The traces are inverted for the slip distribution over the fault plane by applying a linear inversion technique. With the aid of a time-window analysis, we obtain an independent estimation of the source-time function and a more detailed description of the source process. The analysis of the three datasets permits us to deduce the main characteristics of the source process. The rupture initiated at a depth of 16 km and propagated in two directions: updip along the plate interface toward 165° N and toward 70° N. The source duration was between 12 and 14 sec, with the maximum of energy release occurring 8 sec after the initiation of the rupture. The estimated rupture dimension of 35 × 45 km is about one-fourth of the aftershock area. The average dislocation over the fault was 1.4 m (with a maximum dislocation of 4.1 m located 10 km south of the hypocenter), which gives roughly 1 MPa as the average static stress drop.

Frequency‐domain acoustic‐wave modeling and inversion of crosshole data: Part II—Inversion method, synthetic experiments and real‐data results

Geophysics ◽  
1995 ◽  
Vol 60 (3) ◽  
pp. 796-809 ◽  
Author(s):  
Zhong‐Min Song ◽  
Paul R. Williamson ◽  
R. Gerhard Pratt
Keyword(s):  
Frequency Domain ◽  
Real Data ◽  
Forward Modeling ◽  
Two Dimensions ◽  
Inversion Method ◽  
Inversion Algorithm ◽  
Data Set ◽  
Wave Inversion ◽  
Full Wave ◽  
And Inversion

In full‐wave inversion of seismic data in complex media it is desirable to use finite differences or finite elements for the forward modeling, but such methods are still prohibitively expensive when implemented in 3-D. Full‐wave 2-D inversion schemes are of limited utility even in 2-D media because they do not model 3-D dynamics correctly. Many seismic experiments effectively assume that the geology varies in two dimensions only but generate 3-D (point source) wavefields; that is, they are “two‐and‐one‐half‐dimensional” (2.5-D), and this configuration can be exploited to model 3-D propagation efficiently in such media. We propose a frequency domain full‐wave inversion algorithm which uses a 2.5-D finite difference forward modeling method. The calculated seismogram can be compared directly with real data, which allows the inversion to be iterated. We use a descents‐related method to minimize a least‐squares measure of the wavefield mismatch at the receivers. The acute nonlinearity caused by phase‐wrapping, which corresponds to time‐domain cycle‐skipping, is avoided by the strategy of either starting the inversion using a low frequency component of the data or constructing a starting model using traveltime tomography. The inversion proceeds by stages at successively higher frequencies across the observed bandwidth. The frequency domain is particularly efficient for crosshole configurations and also allows easy incorporation of attenuation, via complex velocities, in both forward modeling and inversion. This also requires the introduction of complex source amplitudes into the inversion as additional unknowns. Synthetic studies show that the iterative scheme enables us to achieve the theoretical maximum resolution for the velocity reconstruction and that strongly attenuative zones can be recovered with reasonable accuracy. Preliminary results from the application of the method to a real data set are also encouraging.

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