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Preliminary study on the attenuation characteristics of ground motion recorded during the 2019 Ridgecrest earthquakes

Hongjun Si, Kazuki Koketsu, & Hiroe Miyake

Published August 15, 2019, SCEC Contribution #9710, 2019 SCEC Annual Meeting Poster #246 (PDF)

Poster Image: 
Two major earthquakes, the Mw6.5 and the Mw7.0 Ridgecrest earthquakes occurred about 200 km north-northeast of Los Angeles, California, at 10:33:49 on 4 July and 20:19:53 on 5 July 2019 (PDT), respectively. During these earthquakes, a large amount of ground motion recordings has been observed and opened for public use on the Center for Engineering Strong Motion Data (CESMD). These precious data made it possible to investigate the characteristics of ground motion recorded in Southern California, the United States. In this study, we compare the attenuation characteristics of the strong ground motions of the two earthquakes with the existing GMPEs developed in Japan and the United States, and investigate the spatial distribution of the observed ground motions.

The ground motion data used in this study are those compiled by CESMD. Among these data, the records observed at the stations installed in buildings were excluded. The closest distance from the seismic fault or the median line of the fault to an observation station is defined as the source distances. PGA and PGV are defined as the larger one among the PGAs and PGVs of the two horizontal components. Mw estimated by GCMT are used in the analysis.

As the preliminary results, we compared the PGAs and PGVs observed during the two Ridgecrest earthquakes and the GMPE by Si and Midorikawa (1999), and found that, (1) the observed PGAs for both Mw6.5 and the Mw7.0 earthquakes are generally consists with the predictions; (2) For PGV, the observations are generally also consist with the predictions, while at distances around 180-200 km, some of the PGVs observed in Los Angeles downtown area are relatively larger than the predictions by GMPE.

Key Words
The 2019 Ridgecrest earthquake, Ground motion prediction equation (GMPE); ground motion; PGA; PGV; Response spectra

Si, H., Koketsu, K., & Miyake, H. (2019, 08). Preliminary study on the attenuation characteristics of ground motion recorded during the 2019 Ridgecrest earthquakes. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Ridgecrest Earthquakes