What's Up Hawaii?

   Aloha everyone! It is Monday and time for another look at what is going on in Hawaii. I hope everyone is well. For the people in Chile, my heart goes out to you all after a devastating  8.8 earthquake that hit your country. To everyone that had experienced the tsunami that came afterwards, I am also thinking of you all. That tsunami hit many places. Luckily, even though it was heading right for the Hawaiian Islands, the damage was minimal. It got me thinking though, about other tsunamis that have affected Hawaii and the Islands, so this week I've done an article on six of the tsunamis that were particularly destructive in Hawaii. Also, I'm including a related article on this very thing, tsunamis, from Mike!  ;-)

http://hawaiianlife.com/content/tsunamis-hawaii

                                 *Major Tsunamis In The Hawaiian Islands*

   (1946) There have been six major Tsunamis that have affected the Hawaiian Islands. In the last sixty years, these six have been the most destructive. Generated by a large earthquake near Unimak in the Aleutian chain of Islands of Alaska, one of the most destructive Pacific wide tsunamis and the most severe in the Hawaiian Islands, was the tsunami from the earthquake of 1946.  In the 1930s they used the Richter Magnitude Scale to measure an earthquake, but by the 1970s they had developed the Moment Magnitude Scale. Because of that change, I will give both sizes. They are actually quite different. This earthquake near Unimak was a 7.2 on the scale, but later changed to the new scale and was given an 8.6. It generated one of the most destructive Pacific wide Tsunamis of the 20th century. Huge tsunami waves at Unimak Island reached 35 meters,  more than 100 feet,  above sea level. It completely destroyed the newly built U.S. Coast Guard's Scotch Cap Lighthouse. All five men of its crew were killed. The lighthouse was a steel reinforced concrete structure, and its base was about 30 meters above sea level.

   The tsunami continued on to the Hawaiian Islands and to the north shore of Kauai, about  4 1/2 hours after the earthquake and hit Hilo just under 5 hours later. No warnings went off because they had not yet created a system to warn people. This particular tsunami was damaging to all the Islands, especially the Island of Hawaii. The town of Hilo was slamed with 6 or 7 large waves at about 15 minute intervals. The highest, completely destroyed Hilo's waterfront, killing 159 people. Every home on the main street facing Hilo Bay, was ripped off it's foundation and carried across the street and slammed against buildings. Pololu Valley had waves of over 12 meters, struck a school at Laupahoehoe Point and killed a number of children and also destroyed a hospital. Damage to property was estimated to be over $26 million dollars, and that was in 1946. The loss of life though, was much greater. The tsunami claimed 165 lives that day! In 1948,  the Pacific Tsunami Warning Center was established in Hawaii. This system was expanded in later years and became the International Pacific Warning System.

   (1952) In 1952 a strong earthquake off the coast of Kamchatka Peninsula in the far east of Russia generated a great destructive Pacific wide tsunami. The waves struck the Kamchatka Peninsula, the Kuril Islands, and other areas of Russia's Far East. It caused considerable damage and loss of life. It was very damaging to the Hawaiian Islands. The earthquake was a 8.2 but in later years changed to a 9.0 on the scale. The Hawaii Islands experienced larger waves than most places, from the tsunami. It caused damage on Midway Island. In some areas the waves destroyed boats and piers, knocked down telephone lines, and caused extensive beach erosion. Damage was extensive. Estimates  range from $800,000 to $1,000,000 in 1952. Fortunately though, there was no loss of life!  Tsunami waves of only one meter flooded the streets and buildings on Midway. Travel time was 4.4 hours and the period of waves was 12 minutes.

   On the north shore of Kauai there was damage but not a significant amount.  Oahu's north shore experienced higher waves. Up to 4.5 meters, and in Honolulu the tide gauge recorded only a .7 meter wave. There was talk that the run-up was higher than recorded but photos that were shown later. The tsunami wass powerful enough to throw a cement barge in the Honolulu Harbor into a freighter. It took the Tsunami 6.3 hours to reach Honolulu. The periods of waves were 38 minutes. On Maui, no significant waves were reported from Kahului. The Big Island experienced a run-up to 6.1 meters. Run-up at Hilo was 3.7 meters. A small bridge connecting Coconut Island to the shore was destroyed by one of the waves, lifting it off its foundation, then smashing it down. Travel time was 6.6 hours.  Damage at Hilo was estimated at $.4 million in 1952.

   (1957) Another earthquake hit the Aleutian Islands of Alaska. This one was south of the Andreanof Islands. It was the third largest quake of the 20th century, and it occurred in 1957. It had a moment magnitude of 8.3 on the scale. The earthquake generated  a destructive Pacific wide tsunami, which caused considerable damage at coastal areas in Alaska, British Columbia, Washington, Oregon, and California. Estimates that the tsunami area reached 850 to 900 kilometers long. It was the Hawaiian Islands though, that suffered the most damage.  On Midway Island there was unusual flooding. On Kauai, there was maximum run-up. Damage occurred at the northern part of Kauai, near Haena Point where the waves reached heights of 16 meters. That is almost twice the height of the 1946 tsunami. The waves destroyed bridges and there were sections of Kauai's highways that were flooded. Houses were washed  away and destroyed at Wainiha and Kalihiwai.

   A total of 75 homes were destroyed or badly damaged on Kauai. On Oahu, the maximum waves reached a height of 23 feet. On Molokai, the waves with rup-up heights of 14 feet in Kalaupapa, smashing the water pipeline. At Kahului harbor on Maui, the tsunami induced strong currents and extreme turbulence. At Hilo, on the Big Island, run-up was 3.9 meters. The tsunami flooded the wharf by two feet and damaged the warehouse and its contents. Many buildings at the waterfront were damaged. Coconut Island was covered by one meter of water and the bridge connecting it to the shore as in the 1952 quake, was again destroyed. There was flooding along the coastal streets, but fortunately the 1957 tsunami was nothing like the 1946 tsunami, because there were no loss of lives. Total damage extimates were at 5 million in 1957.

   (1960) The horrific earthquake that hit Chile this past weekend was an 8.8 on the scale, but the Hawaiian Islands luckily were spared from the tsunami that came from this quake. That was not the case back in 1960. The largest earthquake magnitude 9.5 hit off the coast of south central Chile. It generated one of the most destructive Pacific wide tsunamis. The destruction that was experienced throughout the Pacific Ocean was particularly devastating in Chile, Japan, and the Hawaiian Islands.  This tsunami traveled a total distance of more than 6000 miles from the gererating area in southern Chile before reaching the Hawaiian Islands. It took about 15 hours after the quake. The tsunami caused little damage in most of the Hawaiian Islands, but the Island of Hawaii, mainly the Hilo Bay area was hit the hardest. Damages were estimated at $24 million. There were also 61 lives lost that day. 

   The Island of Hawaii was the first of the Hawaiian Islands to experience the effects of the tsunami. The first of eight destructive waves arrived at Hilo Bay, just under 15 hours after the quake. The time period of 12 to 20 minute intervals with seven more large waves had arrived. The maximum run-up at Hilo Bay was 10.7 meters above sea level. The hardest hit was the Waiakea area of Hilo.  A good majority of the downtown of Hilo was destroyed by the waves. Only a few buildings remained standing. The downtown area was severely gutted out.  A total of 61 people were killed and about 540 homes and businesses were destroyed or severely damaged.  Many of the deaths in Hilo occurred in the Waiakea peninsula area which was considered safe because it experienced minimal damage from the 1946 tsunami.

   (1964) The Great Alaskan Earthquake of 1964 generated a great Tsunami, which caused extensive damage in Alaska, along Vancouver Island and in Northern California, but actually caused relatively small damage in the Hawaiian Islands.  At Midway Island the gauge registered only a 0.1 meter change in sea level. On the Island of Oahu, maximum run-up was up to 4.8 meters, but in Honolulu it only measured 0.5 meters. At Kahului, on Maui, maximum run-up was up to 3.7. On the Big Island, rup-up was up to 3 meters, and at Hilo it was recorded at 2.1 meters. The travel times for the Hawaiian Islands were as follows. Midway 4.9 hours, Honolulu 5.3 hours, Kahului 5.2 hours, and Hilo 5.4 hours. The tsunami periods were, Midway 15 minutes, Honolulu 21 minutes, Kahuhui 23 minutes and Hilo 19 minutes. Luckily there was no loss of life in any of the Islands. At Kahului, on Maui damage was estimated at $53,0000. At Hilo on the Big Island, damage was estimated at $15,000 in 1964!

   (1975) In 1975, an earthquake actually struck Hawaii. It was the largest local earthquake to strike the Hawaiian Islands since 1968 and was designated as the Kalapana Earthquake of 1975, the most destructive local tsunami in Hawaii in the 20th century. Actually two quakes occurred. The first at 3:35am local time. With a magnitude 5.7 it was near Laeapuki on Kilauea's south coast on the Island of Hawaii. The second, much larger quake occurred a little over an hour later, 4:48 am.  It had a magnitude 7.2 and was offshore near Kamoamoa, just a few miles east but closer to the shoreline than the earlier foreshock.  It was 8 kilometers below the surface, near the magnatic chambers of the Puna Volcanic rift zone. 

   Although the earthquake was relatively limited, a large tsunami was generated by the second quake. It was destructive along the southern coast of the Island, with less damage along the eastern and western areas. The first tsunami observed by campers at Halape was only 1.5 meters, which is almost 5 feet. The second wave was 7.9 meters,  about 26 feet. It carried the campers inland toward the base of a cliff, where they remained until the tsunami waves subsided.  Nineteen of the campers suffered  injuries and two of them died.  At Hanape, the maximum run-up reached 7.2 meters, which is about 23.5 feet.  The waves were very destructive. Houses were swept off their foundations and properties were extensively damaged.  The pier at Keauhou Landing was completely destroyed.  Maximum run-up of 14.3 meters almost 47 feet high was measured. The remaining areas of the Islands, hit by the tsunami was small.

   Post earthquake surveys of the south coast of the island of Hawaii showed that a large crustal block had slid horizontally towards the ocean and had subsided. Maximum horizontal displacement of approximately 7.9 meters, about 26 feet and vertical subsidence of approximately 3.5 meters about 11.5 feet, occurred near Keauhou Landing. The displacements decreased to the east and west from this area. In fact, subsidence rapidly decreased to the west.  At Punaluu, the shoreline actually uplifted by about 10 centimeters, about 4 inches. Subsequent surveys determined a subsidence of about 3 meters, about 9.8 feet  at Halape Park to the east. A large coconut grove area adjacent to the beach subsided by as much as 3.0 and 3.5 meters, about 10-11.5 feet. Further to the east the subsidence decreased to 1.1 meters, about 3.6 feet at Kamoamoa, 0.8 meters, about 2.6 feet at Kaimu, 0.4 meters, about 1.3 feet at Pohoiki, and 0.25 meters, about 0.8 feet at Kapoho.

   As a result of this quake, the coastline wasn't the only area that was altered.  The summit of Kilauea subsided about 1.2 meters, about 3.9 feet, and moved toward the ocean by about the same amount.  A small short lived eruption took place inside Kilauea's caldera. Inspection of the tide showed wave motion to be upwards at all stations.  The significance of this observation is that the offshore crustal displacement was  an uplift as the onshore section and moved outward.  The dimensions of the sea floor affected by these crustal movemements was approximately 70 kilometers long and 30 kilometers wide. The entire offshore region rose 1.2 meters,  about 3.9 feet. 

   Although the second Kalapana earthquake had a larger surface-wave magnitude of 7.2, relatively minor damage occurred within 10 miles of the epicenter to approximately a dozen residences. However, at Hilo, about 45 miles from the epicenter, earthquake damage was heavy to Hilo Hospital and several other large buildings. The death toll was remarkably low. Only two people lost their lives and 28 other people were injured. Both deaths, all the injuries, and approximately a third of all the property losses, were caused by the tsunami. Total property damage losses from both the earthquake and tsunami were estimated at about $4.1 million. Of the property losses, about $2.1 million was to private property and about $2 million to public property. 

   A local Tsunami Warning was issued by Hawaii's Civil Defense Agency. However, because of the short interval between earthquake occurrence and the arrival of the tsunami, the warning was issued after the first tsunami wave had arrived on the southern part of the island. As mentioned earlier, travel time to Punaluu was only 84 seconds. Since the 1975 tsunami, the population of the southern coast of Hawaii has more than doubled. If a similar quake were to occurr, it would cause greater casualties and property loss. Although the destruction for this weekends earthquake in Chile is unimaginable,  we have to breathe a huge sigh of relief,  for the tsunami that came from that earthquake, that was heading for the Hawaiian Islands, was kind enough to do minimal damage.

   So that's it for this week. It makes you appreciate when Mother Nature is being kind to us! I hope you all stay safe and have a great week. Until next time, Mahalo!

Aloha, 

Di