Geophysics

Earthquake Patterns

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Science  23 Aug 2002:
Vol. 297, Issue 5585, pp. 1239
DOI: 10.1126/science.297.5585.1239d

Locating earthquakes is essential for identifying fault structures and seismic hazards, modeling Earth's deeper structure, and monitoring nuclear detonations. Most methods rely on a one-dimensional velocity model to calculate arrival times of the seismic waves at many stations and a least-squares method to pinpoint the hypocenter by reducing the difference between the observed and calculated arrival times.

Using over 8 million arrival times recorded over the past 35 years, Nicholson et al. have developed a pattern recognition algorithm to locate earthquakes. An event's location is determined by how well its arrival time pattern fits with previous arrival time patterns. They tested this algorithm by relocating 395 nuclear blasts from the Nevada Test Site with greater accuracy than the least-squares method, placing more than 70% of the blasts within 1 km of ground truth depths. The pattern recognition algorithm offers an efficient alternative to the least-squares method because a velocity model is not needed, although small-scale heterogeneities can still be a source of error. — LR

J. Geophys. Res.107, 10.1029/2000JB000035 (2002).

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