1952 Tokachi-Oki Earthquake & Tsunami

The recent September 25, 2003 M 8.3 earthquake near Hokkaido, Japan is located in the same region as the M 8.1 1952 Tokachi-Oki earthquake. During his stay at the USGS as a visiting scientist, Dr. Kenji Hirata (JAMSTEC) led a study examing the slip distribution of the 1952 earthquake using tsunami records. Below are excerpts from the presentation from the 2003 Annual Meeting of the Seismological Society of America on the 1952 Tokachi-Oki earthquake and tsunami. See spatial relationship between the 1952 and 2003 earthquakes.

References:

Hirata, K., Geist, E.L., Satake, K., Tanioka, Y., and Yamaki, S., 2003, Slip distribution of the 1952 Tokachi-Oki earthquake (M 8.1) along the Kuril Trench deduced from tsunami waveform inversion: Journal of Geophysical Research, v. 108, no. B4, p. ESE 6-1 - ESE 6-15.

Geist, E.L., Hirata, K., Satake, K., Tanioka, Y., and Yamaki, S., 2003, Reconciling source areas determine from aftershock and tsunami data: The M 8.1 1952 Tokachi-Oki earthquake along the Kuril subduction zone: Seismological Research Letters, v. 74, p. 221.

see also:
Nanayama, F., Satake, K., Furukawa, R., Shimokawa, K., Atwater, B., Shigeno, K., and Yamaki, S., 2003, Unusually large earthquakes inferred from tsunami deposits along the Kuril trench: Nature, v. 424, p. 660-663.

Photo from the 1952 tsunami. Floating ice was brought onshore during tsunami inundation and damaged structures.

Photo of 1952 tsunami during inundation.

Photo of damage following 1952 tsunami.

Coastline highlighted in orange had observed runup less than 4 m. Red coastline had observed runup greater than 4 m. Star is 1952 epicenter. Circles are aftershocks from 1952 earthquake.

Data from tide gauge stations shown below are used to analyze the 1952 earthquake.

In some cases, ice blocked the tide gauge station and corrupted the record.

Geometry of 1952 rupture. Slip on subfaults A thru J is determined. Depth contours of subducting Pacific Plate indicated at 50, 75, and 100 km. Next slides show profile Q-P.

Results of inversion. Highest slip is on shallow subfaults F and I near trench and subfault E.

Comparison of predicted and observed records.

Comparison of predicted and observed tsunami runup along Hokkaido coastline.

Stress drop distribution derived from slip inversion. Highest stress drop correlates with highest observed seismic intensity.

Generally, aftershocks are located in lower stress-drop regions.

Location of historic earthquake relative to the 1952 Tokachi-Oki rupture. Note that the recent 9/25/03 epicenter is very close to the 1952 epicenter.

Topography of subducting Pacific plate may influence rupture mechanics.

The University of Tokyo Earthquake Research Institute has computed the slip distribution for the 2003 earthquake :

Photo courtesy of University of Tokyo Earthquake Research Institute

(click on image above to go to the ERI page)

Note that the epicenters for the 1952 and 2003 earthquakes are very close to each other. The highest slip for the 2003 earthquake occurs near the 1952 subfaults B and D with low slip (see above), but also near the high slip subfault E. Subfault E may outline an asperity along this fault. Initial tsunami modeling by Tohoku University indicates that highest tsunami amplitudes were in the Cape Erimo region (southern tip of coastline shown above) in contrast to the Kushiro-Kiratappu region for the 1952 tsunami.