NEEDLE & GLOBE

Via BBC, by Jonathan Amos:

It is one of the most exquisite views we have ever had of the Earth.

This colourful new map traces the subtle but all pervasive influence the pull of gravity has across the globe.

Known as a geoid, it essentially defines where the level surface is on our planet; it tells us which way is “up” and which way is “down”.

It is drawn from delicate measurements made by Europe’s Goce satellite, which flies so low it comes perilously close to falling out of the sky.

Scientists say the data gathered by the spacecraft will have numerous applications.

One key beneficiary will be climate studies because the geoid can help researchers understand better how the great mass of ocean water is moving heat around the world.

The new map was presented here in Norway’s second city at a special Earth observation (EO) symposium dedicated to the data being acquired by Goce and other European Space Agency (Esa) missions.

Europe is currently in the midst of a huge programme of EO development which will see it launch some 20 missions worth nearly eight billion euros before the decade’s end.

The Gravity Field and Steady-State Ocean Circulation Explorer (Goce) is at the front of this armada of scientific and environmental monitoring spacecraft.

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Via NASA:

NASA has released the first-ever airborne radar images of the deformation in Earth’s surface caused by a major earthquake — the magnitude 7.2 temblor that rocked Mexico’s state of Baja California and parts of the American Southwest on April 4.

The data reveal that in the area studied, the quake moved the Calexico, Calif., region in a downward and southerly direction up to 80 centimeters (31 inches). The maps can be seen at: http://www.nasa.gov/topics/earth/features/UAVSARimage20100623.html.

A science team at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., used the JPL-developed Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) to measure surface deformation from the quake. The radar flies at an altitude of 12.5 kilometers (41,000 feet) on a Gulfstream-III aircraft from NASA’s Dryden Flight Research Center, Edwards, Calif.

The team used a technique that detects minute changes in the distance between the aircraft and the ground over repeated, GPS-guided flights. The team combined data from flights on Oct. 21, 2009, and April 13, 2010. The resulting maps are called interferograms.

The April 4, 2010, El Mayor-Cucapah quake was centered 52 kilometers (32 miles) south-southeast of Calexico, Calif., in northern Baja California. It occurred along a geologically complex segment of the boundary between the North American and Pacific tectonic plates. The quake, the region’s largest in nearly 120 years, was also felt in southern California and parts of Nevada and Arizona. It killed two, injured hundreds and caused substantial damage. There have been thousands of aftershocks, extending from near the northern tip of the Gulf of California to a few miles northwest of the U.S. border. The area northwest of the main rupture, along the trend of California’s Elsinore fault, has been especially active, and was the site of a large, magnitude 5.7 aftershock on June 14.

UAVSAR has mapped California’s San Andreas and other faults along the plate boundary from north of San Francisco to the Mexican border every six months since spring 2009, looking for ground motion and increased strain along faults. “The goal of the ongoing study is to understand the relative hazard of the San Andreas and faults to its west like the Elsinore and San Jacinto faults, and capture ground displacements from larger quakes,” said JPL geophysicist Andrea Donnellan, principal investigator of the UAVSAR project to map and assess seismic hazard in Southern California.

Each UAVSAR flight serves as a baseline for subsequent quake activity. The team estimates displacement for each region, with the goal of determining how strain is partitioned between faults. When quakes do occur during the project, the team will observe their associated ground motions and assess how they may redistribute strain to other nearby faults, potentially priming them to break. Data from the Baja quake are being integrated into JPL’s QuakeSim advanced computer models to better understand the fault systems that ruptured and potential impacts to nearby faults, such as the San Andreas, Elsinore and San Jacinto faults.

One figure (Figure 1) shows a UAVSAR interferogram swath measuring 110 by 20 kilometers (69 by 12.5 miles) overlaid atop a Google Earth image. Each colored contour, or fringe, of the interferogram represents 11.9 centimeters (4.7 inches) of surface displacement. Major fault lines are marked in red, and recent aftershocks are denoted by yellow, orange and red dots.

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