Changes to magnetic minerals caused by frictional heating during the 1999 Taiwan Chi-Chi earthquake

Toshiaki Mishima, Tetsuro Hirono, Norihiro Nakamura, Wataru Tanikawa, Wonn Soh, Sheng Rong Song

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55 Citations (Scopus)


We carried out magnetic mineral analyses of samples from the shallowest major fault zone within the Chelungpu fault system, which is the zone that previous researchers believe slipped during the 1999 Taiwan Chi-Chi earthquake. Our aim was to gain an understanding of the changes to magnetic minerals during the earthquake. Magnetic hysteresis and low-temperature thermal demagnetization measurements showed that high magnetic susceptibilities in the black gouge zone within the major fault zone could be attributed not to fining of ferrimagnetic minerals but, rather, to their abundance. Thermomagnetic analyses indicated that the strata in and around the fault zone originally contained thermally unstable iron-bearing paramagnetic minerals, such as pyrite, siderite, and chlorite. We therefore concluded that frictional heating (>400°C) occurred in the black gouge zone in the major fault zone during the slip of the Chi-Chi earthquake and that the resultant high temperature induced thermal decomposition of paramagnetic minerals to form magnetite, resulting in the observed high magnetic susceptibilities.

Original languageEnglish
Pages (from-to)797-801
Number of pages5
JournalEarth, Planets and Space
Issue number6
Publication statusPublished - 2009


  • 1999 Taiwan Chi-Chi earthquake
  • Chelungpu fault
  • Ferrimagnetic mineral
  • Frictional heating


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