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April is observed as Earthquake and Tsunami Awareness month
The month of April is observed as earthquake awareness month in the State of California and as tsunami awareness month in the State of Hawaii. Both natural hazards have struck this island with disastrous results, so it is especially important that kama`ainas are reminded, and malihinis are made aware, of these hazards.
April could also be considered earthquake awareness month here in Hawai`i because the largest historical earthquake occurred on April 3, 1868, in the Ka`u district. The estimated magnitude of this event was 7.9, larger than the magnitude-7.8 San Francisco earthquake of April 18, 1906.
The Ka`u earthquake killed a number of people, mainly by a huge landslide near Kapapala and by a tsunami that swept the coastline.
Hawaii's observe tsunami awareness month during April because of the destructive waves that killed 159 people in Hawai`i on April 1, 1946. The tsunami was generated by a magnitude-7.8 earthquake in the Aleutian trench south of Unimak Island. The first wave took 4.9 hours to reach Hilo and caught many residents by surprise. Thereafter, the Seismic Sea Wave Warning System, later called the Pacific Tsunami Warning System, was established to provide residents with an early notification if a distant Pacific basin earthquake triggers a tsunami.
Hawai`i is a geologically dynamic island with two of the most active volcanoes in the world. Directly or indirectly, the volcanoes are the cause of the high seismicity of the island. Monday morning's earthquake belongs to a family of earthquakes generated by the slow crustal adjustment to the load or weight of the volcanoes. The most recent large earthquake from this family was the magnitude-6.2 Honomu earthquake in 1973.
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