An Italian-led team of seismologists has conducted a study comparing a 2007 earthquake off southwestern Portugal with a similar 1755 earthquake.
This year's Feb. 12, magnitude 6 earthquake about 125 miles off southwestern Portugal was compared with the 8.5-8.7 magnitude 1755 quake and resulting tsunami that occurred at the same location.
The researchers said both earthquakes are special because their unique tectonic environment: Although active subduction is likely not occurring at that location, the researchers said brittle plate convergence in old oceanic lithosphere can account for the occurrence of great earthquakes along moderate-length faults.
The scientists discovered this year's earthquake originated 25 miles beneath the sea floor with an oblique reverse faulting source. They also identify the preferred fault plane. They then scaled the source characteristics to the size of the 1755 earthquake and found a fault length of 143- to 196 miles -- compatible with the lengths of mapped faults in the area.
The study that included scientists from the National Institute of Geophysics and Volcanology in Bologna, Italy; University College Dublin; and the University of Granada, appears in the journal Geophysical Research Letters.
Copyright 2007 by United Press International
Related stories:
Siberian quake triggers false US seismic reports
(AP) -- A powerful undersea earthquake off Russia's eastern coast on Monday caused automated monitoring systems to falsely indicate small temblors in Idaho and California, scientists reported.
Scientists find evidence of tsunamis on Indian Ocean shores long before 2004
(PhysOrg.com) -- A quarter-million people were killed when a tsunami inundated Indian Ocean coastlines the day after Christmas in 2004. Now scientists have found evidence that the event was not a first-time occurrence.
6.5 earthquake sparks panic in southern Mexico
A 6.5 magnitude earthquake struck Mexico's southern Chiapas state Thursday, near the Guatemalan border, sparking panic in the region, local officials and US scientists said.
Tectonic fragment linked to Tokyo's quake peril: scientists
A massive slab of rock lurking beneath the Kanto Plain on the central Japanese island of Honshu is a major source of the earthquake threat that dogs Tokyo, scientists said on Sunday.
Biologists hope to kill all of Rat Island's rats
Just one tiny misstep, one goof, and years of planning a $3 million wildlife project will be worthless. Last week, a crew of 18 left Homer aboard the crabber Reliance, bound for little Rat Island at the end of the Aleutian chain on a mission of devastation.
Researchers discover unexpected properties of materials in lowermost mantle
Materials deep inside Earth have unexpected atomic properties that might force earth scientists to revise their models of Earth's internal processes, a team of researchers has discovered.
May 2008 earthquake in China could be followed by another significant rupture
Researchers analyzing the May 2008 Wenchuan earthquake in China's Sichuan province have found that geological stress has significantly increased on three major fault systems in the region. The magnitude 7.9 quake on May 12 has brought several nearby faults closer to failure and could trigger another major earthquake in the region.
New analysis of earthquake zone raises questions
Oregon State University scientists have completed a new analysis of an earthquake fault line that extends some 200 miles off the southern and central Oregon coast that they say is more active than the San Andreas Fault in California.