Gamma Ray and Radon Anomalies in Northern Taiwan as a Possible Preearthquake Indicator around the Plate Boundary

Figure 1

The simplified sketch of the regional map and principal tectonic structures around Taiwan shows that the Philippine Sea Plate (PSP) is moving northwest at 8 cm/yr towards the Eurasia Plate (EP). The circle symbols represent the earthquake epicenter with the focal depths corresponding to different colors from July 1, 2014, to June 1, 2015. The open square represents the location of the YMSG gamma ray station and the TPT radon station. The red lines indicate the active fault proposed by the Central Geological Survey of Taiwan [66]. Seismic events with magnitudes larger than five and some specific earthquakes are labeled and listed in Table 2. The yellow dashed lines indicate the isodepth contours between 10 and 220 km. OT = Okinawa Trough; CeR = central range; CR = costal range; LV = Longitudinal Valley; DF = deformation front.