Hi All. Could this be Petra’s dream? She told me about this dream she had. At the time she didn’t know where this tsunami would occur. I forget the year now, but I will never forget the look on her face when we looked at a poster at the AGU in San Francisco. Her face was completely and totally drained of all color. She saw the location of her dream. She didn’t have to tell me. The look on her face was all I needed to know. It was all I needed to see. Take Care…Don in creepy town

On the evening of July 17, 1998, the villagers in the town of Arop were celebrating the arrival of a three-day national holiday. Feasting was well under way on the narrow spit of land separating the open ocean from Sissano lagoon. When a M> 7.0 earthquake struck the area, the villagers were startled but unhurt. After all, their huts were built on stilts, capable of swaying with the shaking ground.

For most of them they only had a few minutes left, but of course they couldn’t have known this, even though they were told to leave the area.

About 10 minutes later, a loud booming noise coming from the ocean drew many people to the beach to investigate. To their horror, they saw a wall of water nearly 50 feet high rushing towards them at about 40 miles per hour. There was no escape. Within minutes, more than 2,000 people had either drowned or been killed by the force of the water and its accumulated debris. All traces of habitation between ocean and lagoon had vanished—swept bare by the scouring action of millions of tons of water. The devastation at Sissano lagoon was complete. In all, three villages along about six miles of beach were nearly wiped out. Frightened survivors refused for days to descend from the highest inland hills,

A M>7.0 earthquake couldn’t have caused a tsunami of this magnitude. An undersea landslide caused by the earthquake could and did. Coastal towns in Washington, Oregon, and California are not immune to the threat of the unpredictable waves. Within the past century, the northern coast of California, including Santa Cruz, has been hit more than five times by the powerful waves, causing millions of dollars worth of damage and several deaths.

It’s a threat worth considering. A tsunami similar in height and power to the one in New Guinea would easily engulf the Santa Cruz boardwalk, submerging souvenir shops, arcades, and unwary tourists alike. The Giant Dipper, the wooden roller coaster that has thrilled adventure seekers for half a century, would be taken on a wild ride of its own as the mighty wave first toppled it, then swept it out to sea. Much of downtown Santa Cruz would be underwater within seconds.

The landslide theory for New Guinea has disturbing implications for other parts of the world. It suggests that even a relatively small earthquake is capable of causing a huge tsunami, and that the hills and valleys of the ocean floor near a populated beach may be time bombs simply waiting for the appropriate trigger.

Some scientists think that Californians should take note. The Monterey Bay Canyon, less than a mile off the shore of Moss Landing between Santa Cruz and Monterey, has sides sloping sharply down nearly two miles. Such steep drop-offs create ample opportunities for underwater landslides. Additionally, Monterey Bay itself is bisected by two faults, the Monterey Bay fault and the San Gregorio fault.

In 1998, the California Division of Mines and Geology upgraded the San Gregorio to a Class A fault after comparing seismographic history in the region with recent movements detected along the fault line. The upgrade underscores the potential of the fault to rupture and cause an earthquake with a magnitude of M>7.0 or greater. With its new classification, the San Gregorio may be on its way to join its illustrious sisters the San Andreas and Hayward faults as household names for seismically savvy California residents. Keep in mind that the San Gregorio covers the entire entrance to the Monterey Bay and could cause a tsunami to extend across the entire width of the Bay.

http://scicom.ucsc.edu/SciNotes/9901/kill/kill.htm

http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicle/archive/2001/08/14/MN133258.DTL

http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicle/archive/1999/10/15/MN25095.DTL&type=printable