Recent destructive M 8.0 earthquake that struck Solomon Islands on February 6, 2013, as well as ongoing seismic swarm in the area, is fair reminder that we live in a planet that is undergoing constant change.
According to seismologist’s theories of earthquake cycles. the devastating earthquakes that rocked Tohoku, Japan in 2011, Sumatra in 2004 and Chile in 1960 — all of magnitude 9.0 or greater — should not have happened. And that might mean earthquake prediction needs an overhaul, some researchers say.
All those earthquakes, including the latest at Santa Cruz Islands, struck along subduction zones, where two of Earth’s tectonic plates collide and one dives beneath the other. Scientists had thought that earlier earthquakes had released the pent-up strain along Chile’s master fault, meaning no big quakes were coming. Japan and Sumatra both sat above on old oceanic crust, thought to be too stiff for superquakes. When two tectonic plates collide, they build up strain where a fault sticks, or locks, together. Earthquakes release this strain, which is a form of energy.
Massive Sumatra-Andaman earthquake and tectonic plates (Credit: Colonial.net)
For decades, scientists assumed faults acted like rubber bands, steadily building up strain and then releasing it all at once. Some wide accepted models suggested the longer the time since the last earthquake, the larger the next earthquake would be. And records of past quakes, combined with measurements of the speed of Earth’s tectonic plates, suggested the Tohoku and Sumatra-Andaman regions couldn’t make quakes larger than 8.4, almost nine times smaller than a magnitude 9.0 temblor. .
However, seismic activity in recent years showed that subduction faults were capable of producing some of the most destructive earthquakes in recorded history, suggesting earthquake researchers need to re-think aspects of how they evaluate a fault’s earthquake potential.
Researchers failed to recognize that faults could actually store energy. Now, scientists begin to understand that those faults can discharge energy in small amounts, or all at once. So, if a “small” quake hits, it may not release all of the accumulated energy in a fault. A small subduction quake can still register in the magnitude 8.0 range.
Typical subduction zone components (Credit: le.ac.uk)
Chris Goldfinger, a marine geologist at Oregon State University in Corvallis, and his colleagues propose in a study published in the January/February 2013 issue of the journal Seismological Research Letters, that a fault can “borrow” stored energy from previous strain-building cycles, generating larger earthquakes than expected, such as those that hit Sumatra and Tohoku.
Goldfinger said scientists’ failure to recognize that faults could store energy comes from a lack of data. Historic earthquake records go back only 100 years, so in fact, geologists are only now getting histories that reach back thousands of years, via techniques that decode evidence of past earthquakes in sediments.
Goldfinger calls these long-term histories supercycles, and the unusually large and rare earthquakes that discharge the battery are superquakes. The sequence, size and location of quakes vary from one supercycle to the next, he said.
Seismologist Marco Cisternas first proposed that faults could store energy in a 2005′ study that show the magnitude 9.5 Chile earthquake in 1960 (the largest on record) released more energy than had been stored since its most recent quake (in 1837). Data from tsunami deposits in Chile indicate the last superquake occurred in 1575, and smaller quakes since then had only partly released the strain built up on the fault.
And analyses of corals uplifted and killed during Sumatra earthquake, also indicated that the subduction zone undergoes supercycles, according to a 2008 study led by geologists at the Earth Observatory Institute in Singapore. According to that study, each series of quakes in the region lasts between 30 and 100 years, while the supercycles unfold every 200 years or so.
Cascadia Subduction Zone (Credit: USGS)
Goldfinger and his colleagues have evidence that the Cascadia Subduction Zone, which stretches from Northern California to British Columbia, is also in the middle of an earthquake supercycle. Over the past 10,000 years, 19 superquakes and four supercycles have occurred along the zone. There have been 22 additional earthquakes that involved just the southern end of the fault. The force required to shove a piece of ocean crust into Earth’s mantle can produce megaearthquakes along the zone, as in Japan and Sumatra. The Cascadia Subduction Zone has not experienced a major earthquake since 1700, when an estimated 9.0-magnitude earthquake generated an enormous tsunami that killed trees in Puget Sound and traveled across the ocean to Japan.
The model of earthquake energy storage and discharge makes it difficult for scientists to forecast future earthquakes, as there’s no explanation yet for why faults would behave this way. And there is no way to find out how much energy a fault stores.
Massive and deadly M 8.0 earthquake hit Santa Cruz Islands – Tsunami went 500 m inland damaging 3 villages
- The Watchers
Massive subduction earthquake, registered as M 8.0 (USGS/EMSC), hit Santa Cruz Islands at 01:12 UTC onFebruary 6, 2013. The epicenter was located at coordinates 10.752°S, 165.089°E, about 81 km (50 miles) W of Lata, Solomon Islands at depth of 5.8 km (3.6 miles) (poorly constrained). Depth was later revised to 28.7 km by USGS. EMSC is reporting magnitude 7.9 and depth of 20 km.
Update 18:08 UTC : Police in the Solomon Islands report that at least six people have been killed, 3 are missing and approx. 100 homes have been destroyed at a little above sea level areas along the coast.
Due to the relatively close distance to the epicenter (in the epicenter area the waves are moving at high speed) the water swell/current arrived already after approx. 5 minutes. Nearly 800 houses were inundated including the low lying airstrip at Lata.
Update 12:48 UTC : The following paragraphs are from a World Vision report, a religious NGO very active in Asia and the Pacific. The report was made up before the latest casualty numbers were published. This is the most detailed report of what happened since the earthquake struck!
At least 100 homes in Lata have been completely destroyed by a one meter sea surge following today’s 8.0 earthquake, according to Christian humanitarian organization World Vision. Water and electricity remain down as well. Government officials have confirmed four (in the meantime 6) deaths in the islands, and there are unconfirmed reports that some people and fishing boats may have been swept out to sea by the surge. Lata is a township in the Solomon Islands’ Temoto Province that was hardest-hit by Wednesday’s quake.
The majority of Lata’s population (approximately 4,000 people) – including 20 World Vision staff members – have relocated to central Lata, 150 metres above sea level (ER : these quakes are striking since the end of last week and people do not trust it anymore – They may hold their relocation location for many days or even weeks depending on seismicity).
It appears that most families living in Lata were able to relocate before the sea surge. The tsunami warning for the region has now been lifted butsignificant tremors are still being felt throughout Temotu Province. World Vision staff in Honiara were on the phone with their colleagues when the earthquake struck at approximately 12:15 p.m. Wednesday. All staff have been identified and are safe.
Early reports throughout the province indicate water is still knee-deep in some areas.
Lata’s local airport and four surrounding villages (total population: 800) were also flooded by the surge. Some property damage to low-lying homes is also likely.
“I am currently walking through one community [in Lata], and I’m knee-deep in water,” said Jeremiah Tabua, World Vision’s emergency response coordinator in the Solomon Islands. “I can see a number of houses that have been swept away by the surge.”World Vision is coordinating with the Provincial Disaster Management Office, the local Red Cross, and the Temotu Provincial Authority to complete a rapid assessment of the hardest-hit regions. The initial emergency response will likely include providing clean drinking water and clothing, setting up temporary sanitation facilities, and establishing temporary shelters for families who escaped their homes.
Update 10:31 UTC : 42 aftershocks of more than Magnitude 5 since the mainshock. These kind of strong continuous aftershocks are rather exceptional.
Update 10:29 UTC : A lot of people are surprised that a Tsunami of “only” 1 to 1.5 meter can generate this kind of destruction. Many people are having a wrong idea of Tsunamis merely because of the drawings who can be found on the internet. They think that tsunamis have to be huge waves arriving on the coast. In most cases tsunamis are sea swelling with extremely strong currents. The swelling can go on and off for a couple of times, exactly what happened based on testimonies reported in Lata. 2 swells of 1.5 meter can be very destructive on a flat coastal strip.
Update 09:29 UTC : SIBC (Solomon Islands Broadcasting Corporation) reports that up to six people have reportedly died as a result of the tsunami that struck near Temotu Province early this afternoon.
Update 06:00 UTC: Unfortunately the Lata Hospital is expecting further casualties of this tsunami. They have confirmed that around 700 people live in the 3 villages destroyed but many people would have escaped. If we take the Koshimura (2006) percentages seen in Banda Aceh from the 2004 Indian Ocean Tsunami. For a 2m tsunami, the death ratio was around 0.08-0.1 thus around 60-70 deaths would be expected. For a 0.9-1.1m tsunami as reported, the death ratio was around 0.01-0.025 which would mean around 7-18 deaths are to be expected using this function.
Update 05:26 UTC: At least 5 people have been killed in the tsunami. This earthquake is now CATDAT Red. Running on the trend of the tsunami in Japan – 4 of these were elderly victims (2 women, 2 men) and one was a 10-12 year old male.
Update 05:15-05:30 UTC: Nendo is home to around 5000 people and from what can be gathered the destroyed villages are to the west and south of the village of Lata which would mean that around 500 people are likely affected. It is likely that they would have left to higher ground given the intensity of the earthquake, however there is still no word as to their fate. No casualties have as yet been reported.
Update 04:35 UTC: Solomon authorities were telling the BBC that : The wave went 500m inland damaging 3 villages. Houses have collapsed. The messages are dripping in very slowly as all the local authorities have been running for their live uphill.
ER: 500 meter inland, if true, is a huge tsunami, even at “only” 1 meter. Let us hope that most people made it uphill in time. Some older people way have had a hard time in reaching a safe higher location.
Update 04:18 UTC: Local officials in the Solomons said that 2 1.5-meter (4 foot, 11-inch) waves hit the epicenter side of Santa Cruz Island, damaging around 50 homes and properties. (ER)
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| Magnitude | 8.0 |
|---|---|
| Date-Time |
|
| Location | 10.752°S, 165.089°E |
| Depth | 5.8 km (3.6 miles) (poorly constrained) |
| Region | SANTA CRUZ ISLANDS |
| Distances | 81 km (50 miles) W of Lata, Solomon Islands 575 km (357 miles) NNW of Luganville, Vanuatu 581 km (361 miles) ESE of Honiara, Solomon Islands 847 km (526 miles) NNW of Port-Vila, Vanuatu |
| Location Uncertainty | horizontal +/- 15.3 km (9.5 miles); depth +/- 6.9 km (4.3 miles) |
| Parameters | NST=114, Nph=116, Dmin=582.2 km, Rmss=1.48 sec, Gp= 40°, M-type=regional moment magnitude (Mw), Version=7 |
| Source |
|
| Event ID | usc000f1s0 |
Epicenter close view (Credit: EMSC)
After almost a week of increased seismic activity around Solomon Islands, massive M 8.0 was followed by few strong M5+ and M6+. Strong M 6.3 struck Santa Cruz Islands only hour before big quake. In following 60 minnutes after the M 8.0, islands was shaken again by M 6.4 and M 6.6 and numerous M 5+ earthquakes. The earthquakes in this area are triggered by the Australian Plate subducting the Pacific plate.
Tsunami warning was in effect for Solomon Islands, Vanuatu, Nauru, Papua New Guinea, Tuvalu, New Caledonia, Kosrae, Fiji, Kiribati, Wallis and Futuna A Tsunami Watch is in Effect For Marshall Islands, Howland and Baker, Pohnpei, Tokelau, Samoa, Kermadec Islands, New Zealand, American Samoa, Tonga, Australia, Niue, Cook Islands, Indonesia, Wake Island, Chuuk, Jarvis Island, Guam, Northern Marianas, Palmyra Island, Yap, Johnston Island, Minamitorishima, Belau, Midway Island, French Polynesia, Hawaii, Philippines, Japan
Local authorities and Pacific Tsunami Warning Center issued a Regional Tsunami Warning, Watch and Advisory. There were reports of 1 meter high waves around island coastlines. Emergency authorities on Santa Cruz island have confirmed the tsunami has destroyed three villages on the island.
Tsunami travel time map as compiled by NOAA
TSUNAMI BULLETIN NUMBER 008
PACIFIC TSUNAMI WARNING CENTER/NOAA/NWS
ISSUED AT 0347Z 06 FEB 2013
THIS BULLETIN APPLIES TO AREAS WITHIN AND BORDERING THE PACIFIC OCEAN AND ADJACENT SEAS…EXCEPT ALASKA…BRITISH COLUMBIA… WASHINGTON…OREGON AND CALIFORNIA.
… TSUNAMI WARNING AND WATCH CANCELLATION …
THE TSUNAMI WARNING ISSUED BY THE PACIFIC TSUNAMI WARNING CENTER IS NOW CANCELLED FOR
SOLOMON ISLANDS / VANUATU / NAURU / PAPUA NEW GUINEA / TUVALU / NEW CALEDONIA / KOSRAE / FIJI / KIRIBATI / WALLIS AND FUTUNA
THE TSUNAMI WATCH ISSUED BY THE PACIFIC TSUNAMI WARNING CENTER IS NOW CANCELLED FOR
MARSHALL ISLANDS / HOWLAND AND BAKER / POHNPEI / TOKELAU / SAMOA / KERMADEC ISLANDS / NEW ZEALAND / AMERICAN SAMOA / TONGA / AUSTRALIA / NIUE / COOK ISLANDS / INDONESIA / WAKE ISLAND / CHUUK / JARVIS ISLAND / GUAM / NORTHERN MARIANAS / PALMYRA ISLAND / YAP / JOHNSTON ISLAND / MINAMITORISHIMA / BELAU
THIS BULLETIN IS ISSUED AS ADVICE TO GOVERNMENT AGENCIES. ONLY NATIONAL AND LOCAL GOVERNMENT AGENCIES HAVE THE AUTHORITY TO MAKE DECISIONS REGARDING THE OFFICIAL STATE OF ALERT IN THEIR AREA AND ANY ACTIONS TO BE TAKEN IN RESPONSE.
Comments
Yes FW, and also remember what goes up must come down, all that ash is not good to breath and it adds to the smog problem, especially in the ring of fire. he earths magnetic energy as well as the sun and other planets are growing exponentially and thats is effecting our mental abilities as well. But this is part of the Ascension isn't it. Adonai