RED-ACT Report
Real-time Earthquake Damage Assessment using City-scale Time-history analysis
June 17, M5.2 Japan Ibaraki-ken Hokubu Earthquake
Research group of Xinzheng Lu at Tsinghua University ([email protected])
First reported at 08:15, June 17, 2019 (Beijing Time, UTC +8)
Acknowledgments and Disclaimer
The authors are grateful for the data provided by K-NET and KiK-net. This analysis is for research only. The actual damage resulting from the earthquake should be determined according to the site investigation.
Scientific background of this report can be found at:
http://www.luxinzheng.net/software/Real-Time_Report.pdf
1. Introduction to the earthquake event
At 08:00 JST 17 2019 (Local Time, UTC +9), an M 5.2 (JMA) earthquake occurred in Japan Ibaraki-ken Hokubu. The epicenter was located at 140.6 36.5, with a depth of 80.0 km.
2. Recorded ground motions
35 ground motions near to epicenter of this earthquake were analyzed. The names and locations of the stations can be found Table 1. The maximal recorded peak ground acceleration (PGA) is 234 cm/s/s. The corresponding response spectra in comparison with the design spectra specified in the Chinese Code for Seismic Design of Buildings are shown in Figure 1.




Figure 1 Response spectra of the recorded ground motions with maximal PGA
3. Damage analysis of the target region subjected to the recorded ground motions
Using the real-time ground motions obtained from the strong motion networks and the city-scale nonlinear time-history analysis (see the Appendix of this report), the damage ratios of buildings located in different places can be obtained. The building damage distribution and the human uncomfortableness distribution near to different stations is shown in Figure 2 and Figure 3, respectively. These outcomes can provide a reference for post-earthquake rescue work.

Figure 2 Damage ratio distribution of the buildings near to different stations

Figure 3 Human uncomfortableness distribution near to different stations
4. Earthquake-induced landslide of the target region subjected to the recorded ground motions
According to local topographic data, lithology data and ground motion records, the distribution of earthquake-induced landslide near to different stations under the different proportions of the landslide slab thickness that is saturated can be calculated, as shown in Figure 4. The basemap shows the distribution of the local slope. The number in the circle represents the critical slope of the landslide. The earthquake-induced landslide tends to occur with a higher probability when the slope near the station is larger than this threshold value.

(a) The proportion of the landslide slab thickness that is saturated equals 0%

(b) The proportion of the landslide slab thickness that is saturated equals 50%

(c) The proportion of the landslide slab thickness that is saturated equals 90%
Figure 4 Distribution of earthquake-induced landslide near to different stations
Scientific background of this report can be found at: http://www.luxinzheng.net/software/Real-Time_Report.pdf
Table 1 Names and locations of the strong motion stations
No. Station Name Longitude Latitude
1 CHB007 140.227 35.7234
2 FKS006 140.759 37.5031
3 FKS008 140.567 37.4363
4 FKS009 140.635 37.2778
5 FKS013 140.556 37.09
6 FKS014 140.417 36.8864
7 FKS016 140.191 37.1228
8 FKS017 140.369 37.2842
9 FKS018 140.362 37.3961
10 FKS019 140.437 37.603
11 FKS024 140.132 37.3957
12 FKS029 139.38 37.0159
13 FKS031 140.813 37.3364
14 IBR001 140.357 36.7761
15 IBR002 140.707 36.7061
16 IBR003 140.645 36.5915
17 IBR004 140.41 36.5516
18 IBR005 140.237 36.3851
19 IBR006 140.454 36.3665
20 IBR007 140.595 36.3523
21 IBR008 139.983 36.3062
22 IBR012 140.271 36.1954
23 IBR013 140.489 36.1587
24 IBR014 140.195 36.0729
25 IBR017 140.319 35.9537
26 IBR018 140.632 35.977
27 TCG001 140.083 36.9417
28 TCG003 139.715 36.8144
29 TCG005 139.926 36.8061
30 TCG006 140.13 36.7639
31 TCG009 139.715 36.7258
32 TCG013 140.023 36.4368
33 TCG014 140.174 36.545
34 TCG015 139.714 36.7489
35 TCG016 140.156 36.5287
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