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SUMMARY This paper presents a new derivative-free search method for finding models of acceptable data fit in a multidimensional parameter space. It falls into the same class of method as simulated annealing and genetic algorithms, which are commonly used for global optimization problems. The objective here is to find an ensemble of models that… (More)

SUMMARY Monte Carlo direct search methods, such as genetic algorithms, simulated annealing etc., are often used to explore a finite dimensional parameter space. They require the solving of the forward problem many times, that is, making predictions of observables from an earth model. The resulting ensemble of earth models represents all 'information'… (More)

The major cause of sea-level change during ice ages is the exchange of water between ice and ocean and the planet's dynamic response to the changing surface load. Inversion of ∼1,000 observations for the past 35,000 y from localities far from former ice margins has provided new constraints on the fluctuation of ice volume in this interval. Key results are:… (More)

Monte Carlo methods have become important in analysis of nonlinear inverse problems where no analytical expression for the forward relation between data and model parameters is available, and where linearization is unsuccessful. In such cases a direct mathematical treatment is impossible, but the forward relation materializes itself as an algorithm allowing… (More)

[1] It is shown how a change in orientation between the source mechanism of two identically located double couple sources can be estimated from the correlation of the coda waves excited by their sources. The change in orientation is given by the root mean square of the change in strike, Df s dip, Dd and rake, Dl of the double couple. It is not possible to… (More)

[1] Coda wave interferometry (CWI) can be used to estimate the separation between a pair of earthquakes directly from the coda recorded at a single station. Existing CWI methodology leads to a single estimate of separation and provides no information on uncertainty. Here, the theory of coda wave interferometry is revisited and modifications introduced that… (More)

- Malcolm Sambridge, Klaus Mosegaard, Niels Bohr
- 2002

[1] Monte Carlo inversion techniques were first used by Earth scientists more than 30 years ago. Since that time they have been applied to a wide range of problems, from the inversion of free oscillation data for whole Earth seismic structure to studies at the meter-scale lengths encountered in exploration seismology. This paper traces the development and… (More)

- S. Subbey, M. Christie, M. Sambridge
- 2004

Reservoir simulation is routinely employed in the prediction of reservoir performance under different depletion and operating scenarios. Usually, a single history-matched model, conditioned to production data, is obtained. The model is then used to forecast future production profiles. Because the history match is non-unique, the forecast production profiles… (More)

A recently proposed new class of direct search method is applied to the problem of mapping out the region of data-acceptable models (sets of unknowns) in a finite-dimensional nonlinear inverse problem. A model is defined to be data acceptable if its fit to the observed data is better than some prescribed level. The neighbourhood algorithm (NA) can be used… (More)

- T. Nicholson, M. Sambridge
- 2002

[1] A novel approach to hypocenter location is proposed on the basis the concept of pattern recognition. A new data misfit criterion for location is introduced which measures discrepancies between the observed arrival times of an event and those of ''nearby'' previous events. In the arrival pattern misfit measure, travel times predicted by an Earth model… (More)