ESA : Satellites shed new light on earthquakes .- Los satélites arrojan nueva luz sobre los terremotos.....

http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-1/Satellites_shed_new_light_on_earthquakes

Kaikoura quake

 

24 March 2017

Satellite radar scans of last year’s earthquake in New Zealand are changing the way we are thinking about earthquake hazards in regions where our planet’s tectonic plates meet.

The 7.8-magnitude quake that struck New Zealand’s South Island near the town of Kaikoura on 14 November was one of the most comprehensively recorded earthquakes in history.

Immediately after it, a team of scientists from New Zealand, the UK and the US began to study radar images from the Copernicus Sentinel-1 and Japanese ALOS-2 missions to measure the extent of the land movement.

They found that the quake caused the ground to rise by 8–10 m and offset features like roads that crossed the fault by up to 12 m. This caused large landslides and triggered a tsunami.

Satellite radar scans from before and after the quake showed that the ground-based seismic readings were not giving accurate assessments of where the ruptures were occurring.

Seismic readings are based on the shockwaves rippling through Earth. Although they are the quickest way to gather information on earthquakes, they are unable to show details in complex quakes like Kaikoura.

 

3D ground displacement using Sentinel-1 data

 

But radar satellites like Sentinel-1 can detect movements of millimetres in the ground and across wide areas, providing a detailed picture of land deformation and the locations of fault lines.

In the case of Kaikoura, it showed the research team that ruptures took place across many separate faults.

They saw that the complexity and large amount of uplift point towards how mountains in regions such as New Zealand could build rapidly.

“We’ve never seen anything like the Kaikoura quake before – it was one of the most complex ever recorded,” said Professor Tim Wright, study co-author and director of the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics at the UK’s University of Leeds.

“An earthquake commonly ruptures across a single fault line or faults that are closely grouped, but Kaikoura ruptured at least 12 major crustal faults across two distinct active fault domains.

“This challenges many assumptions about how individual faults control earthquake ruptures.”

The study published yesterday in Science has prompted scientists to reassess how many different faults can be involved in a single earthquake, and could potentially help to re-evaluate seismic hazard models.

Sentinel-1

 

“There was growing evidence internationally that conventional seismic hazard models are too simple and restrictive,” said Dr Ian Hamling, a natural hazards geodesist from New Zealand research institute GNS Science and the lead author of the study.

“The message from Kaikoura is that earthquake science should be more open to a wider range of possibilities when rupture models are being developed. It underlines the importance of re-evaluating how rupture scenarios are defined for seismic hazard models. ”

New Zealand’s complex network of faults is similar to those found in western US, Japan and central Asia.

“While earthquakes like Kaikoura’s do not commonly occur, the data we’ve gathered from this event will expand our understanding of similar boundary zones around the world,” said Dr John Elliott from Leeds’ School of Earth and Environment, and co-author.

“Not only could the data help inform us for the future but it may change how we’ve interpreted ancient earthquakes.

“If an earthquake like Kaikoura’s took place thousands of years ago, current methods of paleoseismology would possibly see it as a series of earthquakes over a long period of time, rather than as one large single quake.”

ESA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

Inscríbete en el Foro del blog y participa : A Vuelo De Un Quinde - El Foro!

ESA : Sentinel-1 provides new insight into Italy’s earthquake .- Sentinel-1 proporciona nuevos conocimientos sobre el terremoto de Italia

http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-1/Sentinel-1_provides_new_insight_into_Italy_s_earthquake

Ground displacement from Italy’s earthquake

29 August 2016

On 24 August, an earthquake struck central Italy, claiming at least 290 lives and causing widespread damage. Satellite images are being used to help emergency aid organisations, while scientists have begun to analyse ground movement.

The Italian peninsula is prone to earthquakes because of the continuing collision of the African and Eurasian tectonic plates. Under the Apennine mountain chain, the regional collision is causing the African slab to flex and dip under the Tyrrhenian Sea, while at the same time retreating northeastwards.
The slab's retreat is the main process driving the present tectonic extension which causes earthquakes like this one and the 2009 quake that devastated L'Aquila.

Under the coordination of the Italian Department of Civil Protection, scientists from Italy’s National Institute for Geophysics and Volcanology and the Institute for Electromagnetic Sensing of the Environment of the National Research Council are studying data from the Sentinel-1 satellite mission and other spaceborne radar missions to map surface deformations caused by the earthquake.

 

Italy earthquake deformation

The team found that the main deformation pattern shows subsidence reaching about 20 cm in the Accumoli area, and sideways movement of up to 16 cm.

The scientists use a technique that allows them to map surface deformations by comparing radar images over the affected area taken before and after the event.

The team has benefited from the availability of both Sentinel-1A and Sentinel-1B scans. The scientists were able to quantify the ground movement in both vertical and east–west directions by combining the radar scans obtained as the satellites flew both south to north and north to south.

Sentinel-1 is not the only satellite providing information on this recent quake: scientists are also relying on data from the Italian space agency’s Cosmo-SkyMed satellites, as well as satellite imagery from other space agencies.

In addition, data from a multitude of Copernicus contributing missions are being used to produce maps through the Copernicus Emergency Management Service for damage assessment.

 

Source fault of Italy’s earthquake

 

Sentinel-1 is a two-satellite mission for Europe’s Copernicus environment monitoring programme, led by the European Commission. The first satellite – Sentinel-1A – was launched in 2014, while its sister Sentinel-1B is still in its commissioning phase following launch just four months ago.

With its 250 km-wide swatch over land surfaces, Sentinel-1 gives scientists a broad view of the displacement, allowing them to examine the ground displacement caused by this earthquake and develop the scientific knowledge of quakes.

Once Sentinel-1B is operational next month, it will be possible to perform routine scans over critical areas like Italy every six days with the two-satellite constellation.

Related articles

Nepal earthquake on the radar29 April 2015

Nepal earthquake on the radar29 April 2015 On 25 April, a 7.8-magnitude earthquake struck Nepal, claiming over 5000 lives and affecting millions of people. Satellite images are being used to support emergency aid organisations, while geo-scientists are using satellite measurements to analyse t...

Radar vision maps Napa Valley earthquake02 September 2014

Radar vision maps Napa Valley earthquake02 September 2014 Sentinel-1A has added yet another string to its bow. Radar images from this fledgling satellite have been used to map the rupture caused by the biggest earthquake that has shaken northern California in 25 years.

ESA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
Inscríbete en el Foro del blog y participa : A Vuelo De Un Quinde - El Foro!

nsf.gov - National Science Foundation - : California Central Valley groundwater depletion slowly raises Sierra Nevada mountains

Changes may trigger small earthquakes, scientists find

Water in Southern California's Great Valley flows along the California Aqueduct. Credit and Larger Version

May 14, 2014

Winter rains and summer groundwater pumping in California's Central Valley make the Sierra Nevada and Coast Mountain Ranges sink and rise by a few millimeters each year, creating stress on the state's faults that could increase the risk of an earthquake.

Gradual depletion of the Central Valley aquifer, because of groundwater pumping, also raises these mountain ranges by a similar amount each year--about the thickness of a dime--with a cumulative rise over the past 150 years of up to 15 centimeters (6 inches), according to calculations by a team of geophysicists.

The scientists report their results in this week's issue of the journal Nature.

While the seasonal changes in the Central Valley aquifer have not yet been firmly associated with any earthquakes, studies have shown that similar levels of periodic stress, such as that caused by the motions of the moon and sun, increase the number of microquakes on the San Andreas Fault.

If these subtle seasonal load changes are capable of influencing the occurrence of microquakes, it's possible that they can sometimes also trigger a larger event, said Roland Bürgmann, a geoscientist at the University of California, Berkeley and co-author of the Nature paper.

"The stress is very small, much less than you need to build up stress on a fault leading to an earthquake, but in some circumstances such small stress changes can be the straw that breaks the camel's back," Bürgmann said. "It could just give that extra push to get a fault to fail."

The study, based on GPS measurements from California and Nevada between 2007 and 2010, was led by scientists Colin Amos at Western Washington University and Pascal Audet of the University of Ottawa.

The detailed GPS analyses were performed by William Hammond and Geoffrey Blewitt of the University of Nevada, Reno, as part of a National Science Foundation (NSF) grant. Hammond and Blewitt, along with Amos and Audet, are also co-authors of this week's paper.

"Other studies have shown that the San Andreas Fault is sensitive to small-scale changes in stress," said Amos.

"These appear to control the timing of small earthquakes on portions of the fault, leading to more small earthquakes during drier periods of the year. Previously, such changes were thought to be driven by rainfall and other hydrologic causes."

This work ties overuse of groundwater by humans in the San Joaquin Valley to increases in the height of nearby mountain ranges and possible increases in the number of earthquakes on the San Andreas Fault, said Maggie Benoit, program director in NSF's Division of Earth Sciences, which funded the research.

"When humans deplete groundwater," said Benoit, "the amount of mass or material in Earth's crust is reduced. That disrupts Earth's force balances, causing uplift of nearby mountains and reducing a force that helps keep the San Andreas fault from slipping."

Draining of the Central Valley
Water has been pumped from California's Central Valley for more than 150 years, changing what used to be a marsh and extensive lake, Tulare Lake, into fertile agricultural fields.

In that time, about 160 cubic kilometers (40 cubic miles) of water was removed--the capacity of Lake Tahoe--dropping the water table in some areas more than 120 meters (400 feet) and the ground surface 5 meters (16 feet) or more.

The weight of water removed allowed the underlying crust or lithosphere to rise by so-called isostatic rebound, which may have raised the Sierra as much as half a foot since about 1860.

The same rebound happens as a result of the state's seasonal rains.

Torrential winter storms drop water and snow across the state, which eventually flow into Central Valley streams, reservoirs and underground aquifers, pushing down the crust and lowering the Sierra 1-3 millimeters.

In the summer, water flow into the Pacific Ocean, evaporation and ground water pumping for irrigation, which has accelerated because of drought, allows the crust and surrounding mountains to rise again.

Bürgmann said that the flexing of Earth's crust downward in winter would clamp the San Andreas fault tighter, lowering the risk of quakes, while in summer the upward flexure would relieve this clamping and perhaps increase the risk.

"The hazard is ever so slightly higher in the summer than in the wintertime," he said. "This suggests that climate and tectonics interact, and that water changes ultimately affect the deeper Earth."

High-resolution mapping with continuous GPS
Millimeter-precision measurements of elevation have been possible only in the last few years. Improved continuous GPS networks--part of the NSF EarthScope Plate Boundary Observatory, which operates 1,100 stations around the western United States--and satellite-based interferometric synthetic aperture radar have provided the data.

The measurements revealed a steady yearly rise of the Sierra of 1-2 millimeters per year, which was initially ascribed to tectonic activity deep underground, even though the rate was unusually high.

The new study provides an alternative and more reasonable explanation for the rise of the Sierra in historic times.

"The Coast Range is doing the same thing as the Sierra Nevada, which is part of the evidence that this can't be explained by tectonics," Bürgmann said.

"Both ranges have uplifted over the last few years and both exhibit the same seasonal up and down movement in phase. This tells us that something has to be driving the system at a seasonal and long-term sense, and that has to be groundwater recharging and depletion."

In response to the current drought, about 30 cubic kilometers (7.5 cubic miles) of water has been removed from Central Valley aquifers between 2003 and 2010, causing a rise of about 10 millimeters (2/5 inch) in the Sierra over that time.

-NSF-

Media Contacts Cheryl Dybas, NSF, (703) 292-7734, cdybas@nsf.gov
Robert Sanders, UC Berkeley, (510) 643-6998, rlsanders@berkeley.edu
Mike Wolterbeek, UNR, (775) 784-4547, mwolterbeek@unr.edu
John Thompson, WWU, (360) 650-4502, john.thompson@wwu.edu

Related WebsitesNSF Grant: Revealing the Nature of Contemporary Uplift and Collapse in the Sierra Nevada - Great Basin System (II):
http://www.nsf.gov/awardsearch/showAward?AWD_ID=1252210&HistoricalAwards=false
NSF EarthScope Program:
http://www.earthscope.org/
NSF EarthScope Plate Boundary Observatory:
http://www.earthscope.org/science/observatories/pbo/

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2014, its budget is $7.2 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives about 50,000 competitive requests for funding, and makes about 11,500 new funding awards. NSF also awards about $593 million in professional and service contracts yearly.

 Get News Updates by Email 
Useful NSF Web Sites:
NSF Home Page: http://www.nsf.gov
NSF News: http://www.nsf.gov/news/
For the News Media: http://www.nsf.gov/news/newsroom.jsp
Science and Engineering Statistics: http://www.nsf.gov/statistics/
Awards Searches: http://www.nsf.gov/awardsearch/

The NSF EarthScope Plate Boundary Observatory GPS network is providing millimeter-precision data.
Credit and Larger Version

The GPS station that's part of the NSF Plate Boundary Observatory is pictured on a Nevada summit.
Credit and Larger Version

The Sierra Nevada has gone through kilometers of rock uplift over the last several million years.
Credit and Larger Version

GPS station 311 in the Eastern Sierra Nevada, part of the NSF Plate Boundary Observatory.
Credit and Larger Version

Waning snowpack on the crest of the Sierra Nevada's Twin Peaks, near the Pacific Crest Trail.
Credit and Larger Versión
NASA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@Hotmail.com
ayabaca@yahoo.com
Inscríbete en el Foro del blog y participa : A Vuelo De Un Quinde - El Foro!

nsf.gov - Scientists Discover Layer of Liquified Molten Rock in Earth's Mantle

Hidden magma layer could play role in shaping the geologic face of our planet.-

 

Marine scientists haul in a successfully recovered marine electromagnetic receiver.
Credit: Kerry Key
Download the high-resolution JPG version of the image. (465 KB)
 

Map of the survey region where the research was conducted.
Credit: Scripps Institution of Oceanography
Download the high-resolution JPG version of the image. (499 KB) 


Crew deploying an ocean bottom electromagnetic receiver in the ocean off Nicaragua's shores.
Credit: Kerry Key
Download the high-resolution JPG version of the image. (2 MB)
 

Orange-colored area enclosed by dashed line denotes recently discovered magma layer.
Credit: Scripps Institution of Oceanography
  Download the high-resolution JPG version of the image. (149 KB)


Researchers pull an ocean bottom electromagnetic receiver onto the vessel Melville's deck.
Credit: Kerry Key
Download the high-resolution JPG version of the image. (533 KB)

Scientists have discovered a layer of liquified molten rock in Earth's mantle that may be responsible for the sliding motions of the planet's massive tectonic plates.

The finding may carry far-reaching implications, from understanding basic geologic functions of the planet to new insights into volcanism and earthquakes.

The research was funded by the National Science Foundation (NSF), and is reported in this week's issue of the journal Nature by Samer Naif, Kerry Key, and Steven Constable of the Scripps Institution of Oceanography (SIO), and Rob Evans of the Woods Hole Oceanographic Institution.

"This new image greatly enhances our understanding of the role that fluids, both seawater and deep subsurface melts, play in controlling tectonic and volcanic processes," said Bil Haq, program director in NSF's Division of Ocean Sciences, which funded the work through the NSF Directorate for Geosciences' MARGINS (now GeoPRISMS) Program.

The scientists discovered the magma layer at the Middle America trench off Nicaragua's shores.

Using advanced seafloor electromagnetic imaging technology pioneered at SIO, the scientists imaged a 25-kilometer- (15.5-mile-) thick layer of partially melted mantle rock below the edge of the Cocos plate where it moves beneath Central America.

The new images of magma were captured during a 2010 expedition aboard the research vessel Melville.

After deploying a vast array of seafloor instruments that recorded natural electromagnetic signals to map features of the crust and mantle, the scientists realized they had found magma in a surprising place.

"This was completely unexpected," said Key. "We went out looking to get an idea of how fluids are interacting with plate subduction, but we discovered a melt layer we weren't expecting to find."

For decades scientists have debated the forces that allow the planet's tectonic plates to slide across the Earth's mantle.

Studies have shown that dissolved water in mantle minerals results in a more ductile mantle that would facilitate tectonic plate motions, but for many years clear images and data required to confirm or deny this idea were lacking.

"Our data tell us that water can't accommodate the features we are seeing," said Naif. "The information from the new images confirms the idea that there needs to be some amount of melt in the upper mantle. That's what's creating this ductile behavior for plates to slide."

The marine electromagnetic technology employed in the study was originated by Charles "Chip" Cox, an emeritus oceanographer at SIO, and in recent years further advanced by Constable and Key.

They have been working with the energy industry to apply this technology to map offshore oil and gas reservoirs.

The researchers say their results will help geologists better understand the structure of the tectonic plate boundary and how that affects earthquakes and volcanism.

"One of the longer-term implications of our results is that we are going to understand more about the plate boundary, which could lead to a better understanding of earthquakes," said Key.

The researchers are now trying to find the source that supplies the magma in the newly discovered layer.

The Seafloor Electromagnetic Methods Consortium at SIO also supported the research.

-NSF-

Media Contacts Cheryl Dybas, NSF (703) 292-7734 cdybas@nsf.gov
Mario Aguilera, SIO (858) 534-3624 maguilera@ucsd.edu

Related WebsitesNSF MARGINS (now GeoPRISMS) Program: http://www.nsf-margins.org/
NSF GeoPRISMS Program: http://www.geoprisms.org/

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2012, its budget is $7.0 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives over 50,000 competitive requests for funding, and makes about 11,000 new funding awards. NSF also awards nearly $420 million in professional and service contracts yearly.

 Get News Updates by Email 

Useful NSF Web Sites:
NSF Home Page: http://www.nsf.gov
NSF News: http://www.nsf.gov/news/
For the News Media: http://www.nsf.gov/news/newsroom.jsp
Science and Engineering Statistics: http://www.nsf.gov/statistics/
Awards Searches: http://www.nsf.gov/awardsearch/

 The National Science Foundation (NSF)

Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
 Inscríbete en el Foro del blog y participa : A Vuelo De Un Quinde - El Foro!