Historical Seismograms - Evidence from the AD 2000 Izu Islands ...

3. EarthquakesHistorical Earthquakes and the Seismograms in Taiwan 243Taiwan is located at the center of the western part of the circum-Pacific seismiczone. Therefore, earthquakes are frequent and sometimes strong and destructive.Although Taiwan lies in the active circum-Pacific seismic zone, seismicity patternsshow that three smaller zones exist in the area (see Figure 2):(1) Western Seismic Zone: It starts south of Taipei and extends southward toTainan. The zone is about 80 km in width and runs nearly parallel to the islandaxis. Compared to other two zones, earthquakes here are infrequent, but aftershocksare generally frequent and cause damage over large areas. Focal depths are shallow(about 10 km), and severe crustal movements sometimes occur.(2) Eastern Seismic Zone: It extends from northeast of Ilan on a line south bysouthwest to Taitung, and on to Luzon, Philippine Islands. It forms an arc towardthe Pacific, extends about 130 km in width, and is parallel to the island axis. Inthis zone, earthquakes are frequent, and their hypocenters are deeper than those ofthe western zone.Figure 2. Map showing the Taiwan seismic zones.