John, the experts can't even agree amongst themselves what the cause is, with the expert you're siding with stating it's a 'reasonable explanation' for the cause...... in other words he isn't sure.
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At least six earthquakes registering above a seven on the Richter scale struck a little-known Spanish fault in the recent past, according to new research. The finding suggests that the fault, in Southeast Spain, is more active than previously thought and could pose a potential hazard to people living in the region, according to the study, published in the Geological Society of America Bulletin in October.
The study also found that the fault has given rise to unusual earthquakes. "During earthquakes, the entire length of the fault does not break," said Jose J. Martínez Díaz, a study co-author and researcher at the Complutense University of Madrid, in a statement. "It does so in segments." These ruptures could give rise to larger earthquakes than previously thought.
"This fault has already produced an earthquake of magnitude 6.5 or 7, thousands of years ago, and could do so again tomorrow," Martínez Díaz said. "As a result, it is vital to bear in mind the earthquake-risk calculations and building codes on the area."
The seismic danger in the area has been underestimated because, until now, officials made estimates of earthquake likelihood based on records from only the last 2,000 years, according to the release.
The researchers found evidence for past faults by examining sediments in trenches they dug into the fault, some 100 feet long (30 meters) and 13 feet (4 meters) deep.
The study follows a 5.1 magnitude earthquake in Lorca, Spain, in 2011, which was twice as powerful as was thought possible in the region, according to the release. While some research suggests that groundwater removal caused the Lorca quake, Martínez Díaz is skeptical, pointing out that similar quakes took place in 1674 and 1818, when "aquifer exploitation was not practiced," according to the release.
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A report published in the Nature Geoscience Magazine has concluded that the Lorca, Murcia earthquakes of 2011, were "man made".
A research team headed by Dr Pablo Gonzalez from the University of Western Ontario in Canada has concluded that the seismic activity was caused by the result of excessive amounts of water being drawn from underground sources to feed domestic and agricultural supplies. This loss of water - according to Gonzalez - caused a stress change in the earth's crust along a known major faultline, which was enough to trigger a rupture in the rock.
The result was that in the late afternoon of the 11th of May 2011, an earthquake of 4.5 on the richter scale was followed minutes later by a quake measuring 5.2 which destroyed many historic buildings and claimed 9 lives.
Dr Gonzalez has spent months using satellite data to map the ground deformation caused by the activity before carrying out computer simulations of the fault slip. The results showed a pattern that correlated with stress changes due to loss of groundwater.
Since the 1960s, natural groundwater levels in the region had reduced by 250 metres.
The Scientist concluded that "The presented data and modelling results are consistent with a groundwater crustal unloading process, providing a reasonable explanation for the observed fault slip pattern..."
The subject of water availability and supply has always been a contentious issue for the region of Murcia, where dozens of Golf courses demand an increasing amount of water supply. The fact that the Paramount Pictures theme park at Alhama de Murcia also promises to bring an increased number of tourists to the region can only serve to place a greater strain on demand.
If the issue of groundwater extraction is allowed to go unchecked how long must we wait for the next activty ?