Abstract
Ground motions from normal-faulting earthquakes are generally considered to be smaller than those of strike-slip and thrust events. On 11 April 2011 a crustal normal-faulting earthquake [the Fukushima earthquake (M_w 6.6)] occurred in Eastern Japan. The peak ground acceleration (PGA) observed was considerably higher than the predictions of several ground-motion prediction equations (GMPEs), which were derived mainly from thrust or strike-slip earthquakes. In northeast Taiwan, the tectonic structure of the Ryukyu Arc and the Okinawa Trough typically entail normal-faulting earthquakes. Because of the normal-faulting earthquakes relevance to ground motions and nuclear power plant sites in northeast Taiwan, we evaluated the impact of the ground motion of normal-faulting earthquakes in offshore northeast Taiwan using a newly constructed attenuation relationship for PGA and pseudo-spectral acceleration (Sa). We collected 832 records from 13 normal-faulting earthquakes with focal depths of less than 50 km. The moment magnitude (M_w) of the 13 events was between 4 - 6. The Sa and PGA of normal-faulting earthquakes offshore northeast Taiwan determined with the newly constructed attenuation relationship were higher and lower, respectively, than those obtained using attenuation equations commonly used in the Taiwan subduction zone.
Highlights
Earthquakes are disasters that can cause severe damage and destruction
The comparison of observed peak ground acceleration (PGA) and spectral acceleration (Sa) for normal-faulting earthquakes with two attenuation models indicated that the observed PGA and Sa were more consistent with the new resultant attenuation model for normalfaulting earthquakes than they were with the ground-motion prediction equations (GMPEs) of Lin et al (2012)
To assess the ground shaking impact of normal-faulting earthquakes in offshore northeast Taiwan on three nuclear power plants (NPPs) (NPP-1, NPP-2, and NPP-4), we developed the GMPE for normal-faulting earthquakes with moderate to large sizes in offshore northeast Taiwan
Summary
Earthquakes are disasters that can cause severe damage and destruction. To mitigate the seismic hazard from moderate to large earthquakes, assessing the degree of ground shaking and designing earthquake-resistant buildings is critical. The well-processed 13433 records comprise 61% thrust faulting event records, 32% strike-slip event records, and 7% normal-faulting event records for crustal earthquakes. A total of 9211 earthquake records involve subduction zones; 65% involve thrust faulting, 22% involve strike-slip, and 13% involve normal faulting. In previous studies on Taiwan GMPEs, most equations did not consider the earthquake source faulting types (such as Chang et al 2001; Wu et al 2001; Liu and Tsai 2005). The GMPEs for shallow subduction zone earthquakes (< 50-km depth) only considered thrusting interplate earthquakes. This suggests that most GMPEs that quantify the ground shaking intensity using shallow seismic sources were determined using thrust-faulting and strikeslip earthquakes
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