Abstract
Seismic tomography and receiver function analysis were carried out to investigate the relation between the slab structure in the southern Ryukyu arc region and the occurrence of slow-slip events that repeat biannually. For calculation of the receiver function, 212 teleseismic earthquakes with magnitudes larger than 6.0 were selected, and teleseismic waveforms were observed using two short-period seismometers and one broadband seismometer. Assuming that each later phase in a receiver function was a wave converted from P to S at depth, the time-domain receiver function was transformed into depth domain along each ray path using a reference velocity model. P- and S-wave arrival times, selected manually by the Japan Meteorological Agency (JMA), were used for the analysis of seismic tomography. In all, 6,750 earthquakes from January 2002 to March 2014 were used. The results showed that a cluster of slab earthquakes is distributed about 10 km below the plate interface. This suggests that the slab earthquakes occur in the lower part of the oceanic crust near the oceanic Moho within the slab. Moreover, the fault of the slow-slip events corresponds with the plate interface. The results also showed that a low Vp and high Vp/Vs area is distributed within the subducted oceanic crust underlying the fault associated with the slow-slip events. These structures are similar to those in the Tokai district, which suggests that the thermal condition of the southern Ryukyu arc is similar to the case of a hot-slab area where slow-slip events occur.
Highlights
Seismic tomography and receiver function analysis were carried out to investigate the relation between the slab structure in the southern Ryukyu arc region and the occurrence of slow-slip events that repeat biannually
The plate interface is estimated from the receiver function analysis as dipping northward with an angle ranging from 6° to 14°
Slab earthquakes occur about 10 km below the plate interface where the SSEs occur, which suggests that the slab earthquakes occur in the lower part of the oceanic crust, near the oceanic Moho in the slab
Summary
Seismic tomography and receiver function analysis were carried out to investigate the relation between the slab structure in the southern Ryukyu arc region and the occurrence of slow-slip events that repeat biannually. The depth of the plate interface has been estimated to range from 30 to 45 km using the travel times of reflected S-waves that can be observed via the waveforms of local crustal earthquakes (Nakamura 2001). The area of the low Vp anomaly (−4%), which corresponds to the oceanic crust, is distributed approximately 10 km above the cluster of slab earthquakes at X = −20 km and Y = 10 to 70 km (Figure 4a).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
