An Evaluation of Strong-Motion Parameters at the S-net Ocean-Bottom Seismograph Sites Near the Kanto Basin for Earthquake Early Warning

We analyzed strong-motion records at the ground and borehole in around Kanto Basin seafloor Japan Trench area from three nearby offshore earthquakes of similar magnitudes (Mw 5.8–5.9). The were obtained S-net, which was established to enhance tsunami earthquake early warnings after 2011 great Tohoku-oki disaster. MeSO-net, a dense network seismometers installed depth 20 m Tokyo metropolitan area. K-NET KiK-net networks, 1995 Hanshin-Awaji MeSO-net S-net stations record shakings continuously, while are based on triggering thresholds. It is crucial evaluate properties strong motions recorded by for warning (EEW). This paper compared peak accelerations (PGAs) velocities (PGVs) between K-NET/KiK-net stations. Because borehole, we PGAs significant durations low-frequency (0.1–0.5 Hz) identical lengths. found that horizontal PGVs sites or larger than S wave. In contrast, vertical smaller those Particularly, P-wave parts vertical-component were, average, much records. difference more evident PGAs. average ratios S-wave about 2.5 5 land sites, respectively. two-networks generally comparable. Quantification results dataset may contribute ground-motion prediction EEW design facilities.