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A precise hypocenter determination method using network correlation coefficients and its application to deep low-frequency earthquakes


A knowledge of the precise locations of deep low-frequency earthquakes (LFEs) along subduction zones is essential to be able to constrain the spatial extent of various slow earthquakes and the underlying physical processes. We have developed a hypocenter determination method that utilizes the summed cross-correlation coefficient over many stations, denoted a network correlation coefficient (NCC). The method consists of two parts: (1) an estimation of relative hypocenter locations for every pair of events by a grid search, and (2) a linear least squares inversion for self-consistent relative hypocenter locations for the initial centroid. We have applied this method to ten LFEs in the Tokai region, Japan. Statistically significant values of NCC indicate the relative locations for many pairs, which in turn determine the self-consistent locations. While the catalog depths are widely distributed, the relocated hypocenters fall within a 2-km depth range, which implies that LFEs in the Tokai region occur on the plate interface, similar to LFEs in western Shikoku.


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Correspondence to Kazuaki Ohta.

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Ohta, K., Ide, S. A precise hypocenter determination method using network correlation coefficients and its application to deep low-frequency earthquakes. Earth Planet Sp 60, 877–882 (2008).

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Key words

  • Low-frequency earthquakes
  • precise hypocenter determination
  • cross-correlation coefficient
  • Nankai subduction zone
  • Tokai region