Seismic Event Location: Nonlinear Inversion Using a Neighbourhood Algorithm

Sambridge, Malcolm

doi:10.1007/pl00001158

Cited by 92 publications

(49 citation statements)

References 25 publications

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“…If the number of parameters is very small (smaller than, say, 10), the integral in Eq. 15 can be calculated by sampling r(s) over a predefined regular grid, such as, for example, in the case of the seismic source location problem (WIEJACZ and DE¸BSKI, 2001;LOMAX et al, 2000;SAMBRIDGE and KENNETT, 2001). Otherwise, the stochastic (Monte Carlo) sampling technique has to be used (MOSEGAARD and TARANT- OLA, 1995;BOSCH et al, 2000;DE¸BSKI, 2004).…”

Section: Marginal Pdf Distributionsmentioning

confidence: 99%

Seismic Tomography by Monte Carlo Sampling

Dębski

2009

Pure Appl. Geophys.

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The paper discusses the performance and robustness of the Bayesian (probabilistic) approach to seismic tomography enhanced by the numerical Monte Carlo sampling technique. The approach is compared with two other popular techniques, namely the damped least-squares (LSQR) method and the general optimization approach. The theoretical considerations are illustrated by an analysis of seismic data from the Rudna (Poland) copper mine. Contrary to the LSQR and optimization techniques the Bayesian approach allows for construction of not only the ''best-fitting'' model of the sought velocity distribution but also other estimators, for example the average model which is often expected to be a more robust estimator than the maximum likelihood solution. We demonstrate that using the Markov Chain Monte Carlo sampling technique within the Bayesian approach opens up the possibility of analyzing tomography imaging uncertainties with minimal additional computational effort compared to the robust optimization approach. On the basis of the considered example it is concluded that the Monte Carlo based Bayesian approach offers new possibilities of robust and reliable tomography imaging.

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Section: Marginal Pdf Distributionsmentioning

confidence: 99%

Seismic Tomography by Monte Carlo Sampling

Dębski

2009

Pure Appl. Geophys.

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“…The ETT approach uses a fully automated procedure to allow adaptation to changes in noise and to changes in data density, making it suitable for routine location. Traveltimes for each station and each phase are calculated independently and a global optimisation scheme, such as a grid search or the neighbourhood algorithm (Sambridge & Kennett 2001), is used to find the best hypocentre. Traveltime perturbations can vary abruptly over short distances: consequently, each potential hypocentre has a different ETT prediction for each station.…”

Section: B R I E F Ov E Rv I E W O F E M P I R I C a L T R Av E Lt I mentioning

confidence: 99%

Regional earthquake location using empirical traveltimes in a region of strong lateral velocity heterogeneity

Nicholson¹,

Clarke²,

Townend³

2008

Geophysical Journal International

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S U M M A R YThe unmodelled effects of lateral heterogeneity are a primary cause of earthquake mislocation using routine methods. Approaches that account for the traveltime effects of lateral heterogeneity are a common feature of specialized studies, but some earthquake location methods have been developed that are also suitable for routine location. Here we investigate the use of one such method (3-D empirical traveltimes, ETTs) for local and regional earthquake location in an area of pronounced lateral velocity heterogeneity. We focus on New Zealand and the surrounding region due to the presence of strongly heterogeneous subduction zone environments. The New Zealand example poses significant challenges since most of the seismicity occurs outside the national seismograph network, and many of the observed ray paths traverse the high-velocity subducting slab. We show that in this environment, >60 per cent of the P and S residuals observed when a 1-D model velocity model is used stem from the resolvable lateral heterogeneity signal. For stations that have been in operation for more than five years, 85 per cent of observed residuals can be ascribed to this resolvable signal. We produce consistent 3-D traveltime corrections for all of New Zealand and the surrounding region and demonstrate their application to clusters of earthquakes occurring off the east coast of the North Island.

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“…The importance sampling techniques may be used to find complete, probabilistic solutions to inverse problems. They include the metropolis algorithm (e.g., Mosegaard and Tarantola, 1995), the neighborhood algorithm (e.g., Sambridge, 1999a, b;Sambridge and Kennett, 2001) and the oct-tree algorithm (e.g., Lomax and Curtis, 2001).…”

Section: Introductionmentioning

confidence: 99%

Fast and accurate earthquake location within complex medium using a hybrid globallocal inversion approach

2009

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A novel hybrid approach for earthquake location is proposed which uses a combined coarse global search and fine local inversion with a minimum search routine, plus an examination of the root mean squares (RMS) error distribution. The method exploits the advantages of network ray tracing and robust formulation of the Fréchet derivatives to simultaneously update all possible initial source parameters around most local minima (including the global minimum) in the solution space, and finally to determine the likely global solution. Several synthetic examples involving a 3-D complex velocity model and a challenging source-receiver layout are used to demonstrate the capability of the newly-developed method. This new global-local hybrid solution technique not only incorporates the significant benefits of our recently published hypocenter determination procedure for multiple earthquake parameters, but also offers the attractive features of global optimal searching in the RMS travel time error distribution. Unlike the traditional global search method, for example, the Monte Carlo approach, where millions of tests have to be done to find the final global solution, the new method only conducts a matrix inversion type local search but does it multiple times simultaneously throughout the model volume to seek a global solution. The search is aided by inspection of the RMS error distribution. Benchmark tests against two popular approaches, the direct grid search method and the oct-tree important sampling method, indicate that the hybrid global-local inversion yields comparable location accuracy and is not sensitive to modest level of noise data, but more importantly it offers two-order of magnitude speed-up in computational effort. Such an improvement, combined with high accuracy, make it a promising hypocenter determination scheme in earthquake early warning, tsunami early warning, rapid hazard assessment and emergency response after strong earthquake occurrence.

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Seismic Event Location: Nonlinear Inversion Using a Neighbourhood Algorithm

Cited by 92 publications

References 25 publications

Seismic Tomography by Monte Carlo Sampling

Seismic Tomography by Monte Carlo Sampling

Regional earthquake location using empirical traveltimes in a region of strong lateral velocity heterogeneity

Fast and accurate earthquake location within complex medium using a hybrid globallocal inversion approach

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