The largest island in the Hawai'ian chain just had a series of significant earthquakes. Many people are aware of its history as one of the world's most active volcanoes, but for some reason, people tend to forget it is also not exactly stable. What is going on?
15-OCT-2006 20:35:21-------------4.4----9.9 km---HAWAII
15-OCT-2006 17:14:09-------------5.8----4.6 km---HAWAII
15-OCT-2006 17:07:48-------------6.3----24.0 km--HAWAII
HONOLULU, Hawaii (CNN) -- Sunday morning brought chaos to the normally serene and lush Big Island of Hawaii as it shook with the state's biggest earthquake since 1983.
Registering 6.6 on the Richter Scale, which classifies quakes above 7.0 as "major," the temblor brought down hospital ceilings and hundred-year-old homes. It sent huge rocks and landslides into roadways and knocked out power to thousands.
But miraculously it did not set off a much feared tsunami or, officials said, cost anyone their life.
Like California, Hawaii has a long history of medium to large earthquakes. An excellent source of information is the official USGS webpage. The geologists running this site are very good and they have lots of useful information. Anyone living in an active zone should spend a good few hours reading this entire, very big and complex site. And bookmark it.
One thing everyone must do is educate themselves for obvious emergencies. Just as costal people should understand hurricanes or people living in cold climates, blizzards, so must everyone in dangerous earthquake zones pay attention to their hazards.
Much of the early record of Hawaiian earthquakes comes from the diary of Mrs. Sarah J. Lyman, a missionary's wife at Hilo, on the Big Island of Hawaii. Mrs. Lyman began her account in 1833 and continued it until her death in 1885; this record was then continued for eleven more years by her descendants. About four or five earthquakes per year were reported.
On February 19, 1834, a strong shock threw down stone walls, stopped clocks, upset bottles, and sloshed milk out of half-full pans. Standing and walking were rendered difficult. A similar earthquake occurred on December 12, 1838. No volcanic activity was noted for either event.
There are also tsunami events. Hawaii is very vulnerable to such events even when they happen very far away. The majority of residents of the island chain live within the tsunami destruction belt.
Each year thousands of earthquakes occur in Hawaii, with the majority of them too small to be felt except by highly sensitive instruments. The movement of molten rock within Kilauea or Mauna Loa causes the majority of Big Island earthquakes.
Big Island earthquakes of magnitude 6 or greater tend to occur in clusters with reoccurrence intervals of 10-12 years. Two regions on the Big Island have the potential for a large earthquakes: East Kona and South Kona.
The vast majority of earthquakes happen on the leading edge of the island, the spot where the Pacific Plate hits the stationary plume that has spawned many islands in a long, jagged trail. As the plate moves towards Alaska and Siberia, it grinds over this hot spot and causes eruptions that form new islands. Already, a new island is forming to the east of the biggest island and eventually all the volcanoes on the main island will cool and go dormant and the island will begin eroding away. Eventually, all the previous islands will dissappear under the waves.
Earthquakes occur for similar reasons beneath Mauna Loa's southwest and southeast flanks. The Kealakekua fault zone on Hawaii's Kona coast was the site of an earthquake of about magnitude 6.9 in 1951 that may have been related to the 1950 eruption of Mauna Loa's southwest rift zone. The largest Hawaiian earthquake in recorded history occurred in 1868 beneath the Ka'u district on the southeast flank of Mauna Loa; it had an estimated magnitude of between 7.5 and 8.1. The 1868 earthquake caused damage across the entire island and was felt as far away as the Island of Kauai. The devastation was greatest in the Ka'u district, where an earthquake-triggered mudflow killed 31 people and coastal subsidence produced a tsunami that destroyed several villages. At least 79 people perished during this earthquake; most of these casualties resulted from the landslide and tsunami.
Earthquakes in the Kaoiki region, centered between Kilauea and Mauna Loa, are also thought to be related to stresses in the earth's crust that are produced by the activity of the two volcanoes. In the last half century, earthquakes with magnitudes from 5.5 to 6.6 have shaken the Kaoiki region about once every 10 years. The latest large earthquake in this area had a magnitude of 6.6 and occurred in 1983. This event caused substantial damage to structures in Ka'u, Puna, and North and South Hilo districts. Ground cracking and settling led to temporary road closures, and landslides occurred on steep slopes. The financial losses caused by the earthquake were estimated at $7 million. Fortunately, there were only minor injuries because the earthquake struck early in the morning when most people were still in bed.
Across the Ring of Fire in most lands before 1600, most people built very flimsy houses thanks to these earthquakes. When a frond and paper hut collapses on oneself, there is little injury. When more and more people used gas fires for cooking and other, similar burning substances, when added to mass aggregations of people rather than disbursed populations, huge firestorms accompany earthquakes.
Today, we live in complicated structures with many very heavy elements. Many lands with earthquakes build with mud and stone and earthquakes take terrible tolls when they occur. But in modern civilization, the dangers of fires is greatly amplified because usually the water systems fail and the gas lines blow up at the same time.
This is why American cities out west have to have frequent drills and training sessions for turning off the gas systems when an earthquake happens.
Hawaii doesn't have the same reputation as California for earthquakes. This is due to their desire to make people happy and gay. But one thing is certain: beautiful places are also often dangerous too. This is why it pays to be alert and knowledgable.