BRI

Strong Ground Motions

Earthquake in Bungo Channel on April 17, 2024 (Mw6.2)

IISEE, Building Research InstituteThis report contains preliminary analysis results.

BRIObserved PGAs/PGVs (Horizontal comp.)
cm/s2

558.3 cm/s2
K-NET Uwajima(EHM012)cm/s

21.6 cm/s
K-NET Uwajima(EHM012)554.6 cm/s2
K-NET Sukumo(KOC015)

53.8 cm/s
K-NET Sukumo(KOC015)○: NIED stations, □: JMA seismic intensity stations※ PGA and PGV are the maximum values of vector summation in the horizontal components.

BRIObserved PGAs/PGVs (UD comp.)
cm/s2

539.5 cm/s2
K-NET Sukumo(KOC015)cm/s

11.6 cm/s
K-NET Sukumo(KOC015)○: NIED stations, □: JMA seismic intensity stations

Observed PGAs/PGVs vs GMPE (Si & Midorikawa, 1999)

BRI

NIED stations
JMA stations※ Horizontal axis is not the “shortest distance to the fault”.
※ PGA/PGV values are the larger of the maximum values of NS and EW components.
※ Intraplate earthquake (depth=50 km) is assumed for the estimation.
※ Estimated values beyond 100 km (dashed line) are shown as reference values.

BRI

Attenuation characteristics of response spectra (h=5%)

NIED stations
JMA stations

Pseudo-velocity response (pSv: 1‒2 s, h=5%)

KOC015

Station KOC015 shows the largest
response at period 1–2 s.

BRI

Acc. (cm/s²)

Acceleration

Acceleration Response (h=5%)

Sa-Sd curve (h=5%)

NS (peak: 490.4 cm/s²)
3000

0-600
600

EW (peak: -388.9 cm/s²)

0-600
600

2000

1000

NSEW
1.5s2sUD2.5s0-600
203040Time (s)

5060

701s

NSEW
UD

010

2000

1000

UD (peak: -539.5 cm/s²)

05s0.

3000

Sa (cm/s²)

600

BRI

Sa (cm/s²)

Acc. (cm/s²)

Acc. (cm/s²)

Ground motion at KOC015

0080123Period (s)450510Sd (cm)15202024/04/17 23:14:41 at KOC015: K-NET station, Intensity: 6.0

Acc. (cm/s²)

Acceleration

3000

NS (peak: 555.5 cm/s²)

Acceleration Response (h=5%)

3000

Sa-Sd curve (h=5%)
0.
5s

600

BRI

0-600
600
0-600
600

2000
Sa (cm/s²)

2000
EW (peak: 430.6 cm/s²)

Sa (cm/s²)

Acc. (cm/s²)

Acc. (cm/s²)

Ground motion at EHM012

10001000UD (peak: 144.3 cm/s²)

0NS
1.5s
EW2s
2.5s
UD0-600010203040Time (s)50602024/04/17 23:14:39 at EHM012: K-NET station, Intensity: 5.4701s

NSEW
UD80

00123Period (s)450510Sd (cm)1520

Response acceleration spectrum Sa and response periods
Colored Line: Taiwan Earthquake strong-motion(Equivalent damping factor＝5％)

Sa - Sd curve and response periods
Colored Line: Taiwan Earthquake strong-motion(Equivalent damping factor＝15％)

BRIBRI
Base shear coefficient CB＊(＊effective mass conversion)

SummaryBRI• K-NET station KOC015 (Sukumo) showed larger PGA and PGV.
• The response acceleration (Sa) of the North-South (NS) components of KOC015(Sukumo) showed large values at around the period of 0.5 s.
• From the Sa-Sd curve assuming a 15% equivalent damping ratio, the Sa-Sd shapesof this earthquake were smaller than past major earthquakes in Japan.
Acknowledgments:
We used K-NET and KiK-net strong-motion data provided bythe National Research Institute for Earth Science and Disaster Resilience; NIED), Japan (https://www.doi.org/10.17598/NIED.0004)
We also used strong-motion data from the Japan Meteorological Agency (JMA) seismic intensity stations.
We used hypocenter information determined by NIED Hi-net.
Response spectra were calculated using the subroutine program developed by Osaki (1994).
Figures were prepared using Generic Mapping Tools (GMT: Wessel and Smith, 1998).
We used strong motion data provided by NIED (K-NET and KiK-net), JMA, and RTRI for past strong motion in Japan.
Sa-T and Sa-Sd were calculated using the View Wave by Kashima, BRI.