Japan 1896 Meiji-Sanriku earthquake

Location:
         The epicenter of this earthquake lies just to the west of the Japan Trench, the surface expression of the west-dipping subduction zone that forms part of the convergent boundary between the Pacific and Eurasian plates.

Characteristics:
        The unusual disparity between the magnitudes of tsunami and earthquake in such an event has led to two possible explanations;

• The tsunami was caused by a slope failure triggered by the earthquake
• The rupture velocity was unusually low

Tanioka and Sataka (1996) proposed that in this case the effect of subducted sediment beneath the accretionary wedge was responsible for a slow rupture velocity. They modelled the effects of a 20° dipping fault along the top of the subducting plate and found that they could match both the observed seismic response and tsunami, but required a displacement of 10.4 m^. The displacement can be reduced to a more reasonable value by considering the extra uplift caused by the deformation of sediments in the wedge and a shallower fault dip of 10°. This revised fault model gives a magnitude of M_w=8.0-8.1, much closer to the estimated tsunami magnitude.

Tsunami:
At 7:30 pm on June 15, families were celebrating the return of soldiers from the Sino Japanese War and a Shinto holiday when they felt a small earthquake. There was little concern because it was so weak and there had been many small tremors in the previous few months. About 35 minutes later the Sanriku coast was struck by the first wave of the tsunami, followed by a second a few minutes later. The tsunami damage was particularly severe because it coincided with high tide. Wave heights of up to 38.2 meters (125 ft) were measured. Nearly 9,000 homes were destroyed and 22,066 deaths were recorded. Most deaths occurred in Iwate and Miyagi, although casualties were also recorded from Aomori and Hokkaido. An unusual number of the victims were found with fractured skulls and limbs either broken or missing, testifying to the power of the tsunami. As was their normal practice each evening, the local fishing fleets were all at sea when the earthquake struck. In the deep water the wave went unnoticed, and when they returned the next morning they found themselves sailing amongst a mass of debris and bodies.
The tsunami also caused damage in Hawaii where wharves were destroyed and several houses swept away, wave heights of up to 9 meters (30 ft) were measured.