Initial Investigation of the May 24, 1994 Hualien and June 5, 1994 Nanao Earthquakes

  • Author(s): Kuo-Fong Ma and Masayuki Kikuchi
  • DOI: 10.3319/TAO.1994.5.4.611(T)
  • Keywords: IRIS Slow earthquake Stress drops
  • Citation: Ma, K.-F. and M. Kikuchi, 1994: Initial Investigation of the May 24, 1994 Hualien and June 5, 1994 Nanao Earthquakes. Terr. Atmos. Ocean. Sci., 5, 611-623, doi: 10.3319/TAO.1994.5.4.611(T)

 

Abstract

We investigate the characteristics of the May 24, 1994 Hualien and June 5, 1994 Nanao earthquakes using the long period P-wave data recorded by the IRIS (Incorporated Research Institution r Seismology). The solution based on long period P waves gives a mechanism with dip=23.6°, rake=-31.4° and strike=135.3°, and a seismic moment of 9.0x1025 1.3x1026 dyne-cm (Mw=6.6~6.7) for the Hualien earthquake; and with dip=62.6°, rake=25.0° and strike=293.2°, and a seismic moment of 3.73x1025dyne-cm (Mw=6.4) for the Nanao earthquake. The source time-function of the May 24, 1994 Hualien earthquake consisted of a main event with a time duration of 8 sec followed by two small subevents extending the total duration of the source time-function to 35 sec. This long duration of source ·time function and the difference between Ms and mb suggest the Hualien earthquake was a slow earthquake. The source time function of the June 5, 1994 Nanao earthquake had a time duration of 6 sec and was rather simple compared with Hualien earthquake. The average slips on the fault for the Hualien and Nanao earthquakes were 40~92.3 cm and 51.8 cm, respectively. The stress drops of the two intra-plate events were comparable to those of most large earthquake.

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