Sat Mar 23, 2024 11:33 pm by globalturbo
Lorca earthquake ’caused by groundwater extraction’
The relatively modest Magnitude 5.1 quake resulted in extensive damage and nine deaths
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Scientists studying the
fault beneath the Spanish city of Lorca say that groundwater removal may
be implicated in a deadly 2011 earthquake there.
Detailed surface maps from satellite studies allowed them to infer which parts of the ground moved where.
They report in Nature Geoscience that those shifts correlate with locations where water has been drained for years.
The study highlights how human activity such as drainage or borehole drilling can have far-reaching seismic effects.
Pablo Gonzalez of the University of Western Ontario and colleagues
used satellite radar data to trace the ground movements of the Lorca
event back to their source, finding that the earthquake resulted from
slippage on a comparatively shallow fault that borders a large water
basin south of the city.
That the slippage happened at a depth of just 3km explains why the
fairly mild Magnitude 5.1 quake caused so much damage in the area.
The team went on to study potential reasons for the slippage, finding
that the water table in the adjacent Alto Guadalentin basin had dropped
by some 250m over the last 50 years as water was drained for irrigation
in the region.
Their calculations show that this created stresses on the fault that
initially triggered the earthquake and defined its eventual magnitude.
Geoengineering dreamsHowever, the
area lies on a seismically active region, and the data suggest only that
the water drainage sped up and eventually triggered a process that
would have eventually happened anyway.
“Start Quote
Dr Gonzalez stressed the study was specific to
the Lorca earthquake, telling the Reuters news agency that “we cannot
set up a rule just by studying a single particular case”.
“But the evidence that we have collected in this study could be
necessary to expand research in other future events that occur near…
dams, aquifers and melting glaciers, where you have tectonic faults
close to these sources.”
In an accompanying Nature Geoscience article,
Jean-Philippe Avouac of the California Institute of Technology said:
“It does not take much to trigger an earthquake – even strong rainfall
can do the job”.
“Numerous examples of seismicity triggered by the impoundment of
reservoir lakes, hydrocarbon extraction, quarrying and deep well
injections have been documented over the years.”
Previous research has suggested that the fluid injection associated
with the controversial practice of gas extraction by hydraulic
fracturing or “fracking” was linked so specific earthquake events.
If science can pin down exactly how stresses from anthropogenic
sources distribute and contribute to seismic events, Prof Avouac
suggested, “we might dream of one day being able to tame natural faults
with geoengineering”.
“For now, we should remain cautious of human-induced stress
perturbations, in particular those related to carbon dioxide
sequestration projects that might affect very large volumes of [the
Earth's] crust.”
BBC News – Lorca earthquake ’caused by groundwater extraction’.
Thanks to: http://2012indyinfo.com
The relatively modest Magnitude 5.1 quake resulted in extensive damage and nine deathsRelated Stories
- Destruction and shock in Spain’s earthquake ‘hot zone’
- Spain shocked by fatal earthquake
- Thousands flee Spanish quake town
Scientists studying the
fault beneath the Spanish city of Lorca say that groundwater removal may
be implicated in a deadly 2011 earthquake there.
Detailed surface maps from satellite studies allowed them to infer which parts of the ground moved where.
They report in Nature Geoscience that those shifts correlate with locations where water has been drained for years.
The study highlights how human activity such as drainage or borehole drilling can have far-reaching seismic effects.
Pablo Gonzalez of the University of Western Ontario and colleagues
used satellite radar data to trace the ground movements of the Lorca
event back to their source, finding that the earthquake resulted from
slippage on a comparatively shallow fault that borders a large water
basin south of the city.
That the slippage happened at a depth of just 3km explains why the
fairly mild Magnitude 5.1 quake caused so much damage in the area.
The team went on to study potential reasons for the slippage, finding
that the water table in the adjacent Alto Guadalentin basin had dropped
by some 250m over the last 50 years as water was drained for irrigation
in the region.
Their calculations show that this created stresses on the fault that
initially triggered the earthquake and defined its eventual magnitude.
Geoengineering dreamsHowever, the
area lies on a seismically active region, and the data suggest only that
the water drainage sped up and eventually triggered a process that
would have eventually happened anyway.
“Start Quote
Jean-Philippe Avouac California Institute of Technology
We should remain cautious of human-induced stress
perturbations, in particular those related to carbon dioxide
sequestration projects”
Dr Gonzalez stressed the study was specific to
the Lorca earthquake, telling the Reuters news agency that “we cannot
set up a rule just by studying a single particular case”.
“But the evidence that we have collected in this study could be
necessary to expand research in other future events that occur near…
dams, aquifers and melting glaciers, where you have tectonic faults
close to these sources.”
In an accompanying Nature Geoscience article,
Jean-Philippe Avouac of the California Institute of Technology said:
“It does not take much to trigger an earthquake – even strong rainfall
can do the job”.
“Numerous examples of seismicity triggered by the impoundment of
reservoir lakes, hydrocarbon extraction, quarrying and deep well
injections have been documented over the years.”
Previous research has suggested that the fluid injection associated
with the controversial practice of gas extraction by hydraulic
fracturing or “fracking” was linked so specific earthquake events.
If science can pin down exactly how stresses from anthropogenic
sources distribute and contribute to seismic events, Prof Avouac
suggested, “we might dream of one day being able to tame natural faults
with geoengineering”.
“For now, we should remain cautious of human-induced stress
perturbations, in particular those related to carbon dioxide
sequestration projects that might affect very large volumes of [the
Earth's] crust.”
BBC News – Lorca earthquake ’caused by groundwater extraction’.
Thanks to: http://2012indyinfo.com
