1. The setting of standard seismic waves to enable evaluation of the earthquake-resisting performance of existing railway facilities

  • Categorization of Japanfs prefectures into two groups by the type of dominant earthquake, one characterized by inland active fault-type earthquakes and the other by submarine trench-type earthquakes (each allotted a standard seismic wave), to allow evaluation of the earthquake-resisting performance of railway facilities

Methods have not been integrated to evaluate the earthquake-resisting performance of civil engineering structures, architecture to accommodate passengers or trolley wire poles. To evaluate the earthquake-resisting performance of these railway facilities under the same external force, therefore, the Railway Technical Research Institute (RTRI) adopted standard seismic waves.

In order to obtain indexes to determine the seismic waves that should be used in evaluating earthquake-resisting performance, the RTRI analyzed levels of earthquake hazard in different areas across the country. The most influential earthquake in each area was extracted, and Japanfs prefectures were classified into two groups, one significantly prone to the influence of inland active faults and the other to the influence of submarine trenches in seismology (Fig. 1). The RTRI assumed an M7-class earthquake (with a magnitude of 7) at the epicenter for the former and an M8-class earthquake occurring at a point about 60 km distant for the latter. For earthquakes occurring closer to land than the above, therefore, further separate discussions are required.

By performing earthquake response analysis for the above-mentioned railway facilities under different seismic waves, the RTRI found that earthquake motion at 1 to 5 Hz (a period of 0.2 to 1.0 sec) with a flat and continuous amplitude was the most appropriate in evaluating the earthquake-resisting performance of railway facilities. Based on this finding, the RTRI made a standard seismic waveform for earthquakes of the inland active fault type and another for earthquakes of the marine trench type by correcting previous earthquake records with respect to the scale of the earthquake and the distance to the epicenter (Fig. 2). The standard seismic waveform for the former features several pulses of short duration and large acceleration, while that for the latter has approximately constant amplitudes of 20 to 30 seconds. The RTRI applies one of the seismic waveforms in Fig. 2 depending on the classification to which the object area belongs. As the standard seismic waveforms set above represent maximum values, they shall be reduced depending on the actual seismic activity in the intended area and the distance from the epicenter fault.

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