INDEX - SCIENCEwww.islandbreath.org ID#0509-01
SUBJECT: KAUAI TSUNAMI
SOURCE: JUAN WILSON firstname.lastname@example.org
POSTED: 04 JANUARY 2005 - 8:00am.HST
It has and will again happen here
1957 tsunami hitting what was the town on Kalihiwai on Kauai's north shore.
Arrows point to utility poles awash in ocean water
Kauai's recent history with tsunamis
by Juan Wilson on 4 January 2005
The tsunami disaster that hit the Indian Ocean is mind-boggling and emotionally devastating. The scale of suffering in so short a time can only be compared to the attacks on Hiroshima and Nagasaki with atomic bombs in 1945. Total instant destruction! This disaster dwarfs what America experienced on 9/11/2001 by a hundred fold.
Compared to the 2004 tsunami in the Indian Ocean the recent history of tsunamis in the Pacific Ocean is insignificant. However, the potential for destruction here is just as real. Hawaii, of course, is in the middle of the Pacific. The Pacific Ocean is rimmed with fault lines from Japan, to the Aleutians, California, Peru, and back around to Indonesia.
Tsunamis generated at the rim can take four or five hours to reach Hawaii, with any luck giving us sufficient time to head for the hills.
Landslide residue in Aleutian Islands that caused Pacific Ocean tsunami
In my lifetime there have been two significant tsunamis that have hit Kauai. Fortunately for me I was not here for either. Both tsunamis were generated in the Aleutian Islands.
The first was in 1946. The major damage from that tsunami was on the Big Island. There is did extensive damage to Hilo, Laupahoehoe and Waipio Valley.
People running from tsunami churning through the palm trees near Hilo Bay 1946
According to www.Pacificworlds.com, "the 1946 tsunami hit with two powerful waves, with a maximum run-up of forty-five feet in elevation. All the bridges at Wainiha were washed out, and the tiny village of Wainiha itself was flattened. At Haena , most of the damage occurred on the flat at the Wainiha end of the ahupua‘a. At least fourteen people died, including many children, and several homes were washed away."
They go on to say that "in 1957 seventy-five homes were demolished or damaged along the 15 mile strip between Kalihiwai and Haena -- including 25 of 29 at Haena itself -- leaving around 250 persons homeless. Six Kaua‘i bridges were washed out, including the bridge at Kalihiwai, isolating 1,000 persons on the Haena end of the road. Fortunately, no deaths or injuries resulted from this event."
The remains of Kalihiwai bridge after 1957 tsunami hit Kauai's north shore
The following are the heights of ocean inundation, above sea level, reached during 1946 tsunami that hit Kauai.
Nawiliwili 9 feet
Kalihiwai, 18 feet
Wainiha 36 feet
Haena 45 feet
The event we have not prepared for is a tsunami generated in the Hawaiian Islands themselves. A major landslide, above or below the ocean surface, could generate a huge tsunami. Without forewarning such an event would create a wave that would travel from one end to the other of the inhabited islands within minutes, not hours.
It is possible that new GPS monitoring technology could give Hawaii sufficient warning of earth movements to be useful, but that technology is only being evaluated now.
It has been revealed only recently how extensive landslides have been in the history of the Hawaiian islands. In the following computer-generated map of Oahu, the Nuuanu landslide is seen. Debris, amounting to nearly a third of the island of Oahu, fell off the Windward side. The data was compiled by J.R. Smith and Terri Duennebier
from underwater mapping done by the University of Hawaii.
One thing is clear, the events in the Indian Ocean demonstrate how fragile our lives are living on islands in oceans that occasionally have large ripples.
Silent Volcanic Quakes Could Portend Tsunamis
by Sarah Graham published in Scientific American 28 Feb 2002
Nearly 15 months after the fact, scientists have discovered a magnitude-5.7 earthquake that occurred on Hawaii's Kilauea volcano. According to a report published today in the journal Nature, the 36-hour-long quake forced the southern flank of the volcano to slide nearly nine centimeters into the sea. Although no one felt it, such seemingly subtle quakes can potentially set in motion events leading to a tsunami.
Peter Cervelli of Stanford University and his colleagues detected the aseismic earthquake using a network of global positioning system (GPS) stations strewn around the volcano on Hawaii's Big Island. "We call them silent earthquakes because the ground doesn't shake and they produce no seismic waves," co-author Paul Segall explains.
As a result of the quake, a 2,000-cubic-kilometer section of the southeast side of the volcano moved seaward, achieving a maximum speed of six centimeters a day before coming to rest. When the side of the volcano doesn't halt in such circumstances and instead slips off into the ocean, a so-called flank collapse occurs. Because of the volume of rock involved, flank collapses can trigger tsunamis. "This event did not produce a tsunami," Segall says, "but if we can detect potentially catastrophic ground motion in its early stages, we might be able to issue tsunami warnings in the future."
As the new findings indicate, GPS networks are capable of identifying silent quakes in areas not previously known to experience the events. Now that they know such movement is possible, the authors propose that the monitoring data could be analyzed in real time so that warnings could be issued in cases of sudden acceleration or potential instability. Writing in an accompanying commentary, Steven N. Ward of the University of California at Santa Cruz agrees, noting that the "world's oceanic volcanoes are stages best not left unwatched." He adds, however, that "people should not lose sleep over large but rare natural hazards."