Seismic quiescence before the 2003 Tokachi‐oki earthquake

Abstract

Some studies have found evidence of seismic quiescence, periods with fewer small earthquakes than normal, before the occurrence of some large earthquakes. In a new case study, Katsumata reexamined data from an earthquake catalog to study seismic activity preceding the magnitude 8 Tokachi‐oki earthquake that occurred on 26 September 2003 off the Pacific coast of Hokkaido. The author's statistical analysis showed that there was a clear, significant decrease in seismic activity in the region during the 4 years leading up to the Tokachi‐oki earthquake. This period of quiescence was similar in length to several other quiescence periods reported before other earthquakes. Further studies and improved seismic monitoring will be needed to determine how common precursory seismic quiescence is. (Journal of Geophysical Research‐Solid Earth, doi:10.1029/2010JB007964, 2011)