Ground Deformation from the South Napa Earthquake

NASA’s Jet Propulsion Laboratory, Pasadena, California, has been monitoring active earthquake faults in California with a number of remote sensing and ground-based techniques. One such technique is the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) instrument, which has been in use since 2009. UAVSAR is an L-band Interferometric Synthetic Aperture Radar instrument that flies mounted underneath a NASA C-20A Earth science research aircraft from NASA’s Armstrong Flight Research Center in Edwards, California. UAVSAR is able to detect minute changes in Earth’s surface that occur over time between flights of the instrument.

UAVSAR has monitored much of California’s seismically active regions including the Napa area about every six months since November 2009. The temporal history is key to identifying and understanding change when an event, such as an earthquake occurs. A comparison of data collected May 29, 2014, three months before the earthquake, and data collected August 29, 2014, five days after the magnitude 6.0 South Napa earthquake on August 24, 2014, determined that the earthquake surface rupture was more complex than originally anticipated with motion on multiple strands of the fault near the earthquake’s epicenter. The colors in the image represent the amount of ground motion between the two flights in the direction from a point on the ground to the instrument, which flies at an altitude of 41,000 feet (12,497 meters). Each colored contour, or fringe, of the image represents 4.7 inches (12 centimeters) of ground displacement toward or away from the instrument. These preliminary results indicate that several inches/centimeters of horizontal slip occurred on the various strands of the fault. In addition, linear discontinuities in the colored zones indicate locations where surface rupture is highly likely and these are of profound concern. The exquisite detail of the UAVSAR imagery provides local, state and federal agencies with the exact location of the fault traces that shifted during the earthquake and how they relate to levees, buildings, roads, and other vital infrastructure, as well as to help provide a fundamental understanding of earthquakes processes.

Further analyses of UAVSAR data will reveal how deep under Earth’s surface the faults slipped and the amount of the slip. Initial GPS analyses (yellow arrows), indicate an average slip of nearly 23.6 inches (60 centimeters) along a 9.3-mile-long (15-kilometer) fault, which is equivalent to a magnitude 6.1 earthquake, suggesting that additional quiet (non-shaking) slip occurred along the fault following the main earthquake.

Image credit: NASA/JPL-Caltech/ASI/Google Earth

Note: For more information, see PIA18798: NASA Analyses of Global Positioning System Data and Italian Radar Satellite Data Reveal Napa Quake Ground Deformation and NASA Research Aids Response to California Napa Quake.

Ubinas Volcano, Peru

This false-color image of Peru's Ubinas volcano was acquired on April 14, 2014, by NASA's Uninhabited Aerial Vehicle Synthetic Aperture Radar, or UAVSAR. Located about 100 miles (160 kilometers) from the city of Arequipa, Ubinas is Peru's most active volcano.

UAVSAR flew exactly the same flight path over Ubinas in 2013. By combining the images from the two years, researchers will produce detailed maps of surface motions that can improve models of volcanic deformation.

Image credit: NASA/JPL-Caltech

Surface Displacement Map for 28 March 2014 La Habra Earthquake

Scientists at NASA's Jet Propulsion Laboratory, Pasadena, California, developed a model of the March 28, 2014, magnitude 5.1 La Habra, California earthquake, based on the distribution of aftershocks and other seismic information from the U.S. Geological Survey. This image shows what the earthquake may look like to an interferometric synthetic aperture radar, such as NASA's Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR).

The earthquake is believed to be associated with the Puente Hills Thrust fault, which zig-zags from Orange County northwest through downtown Los Angeles. The NASA model is based on a fault estimated to be 9 kilometers long, 5 kilometers deep and 3 kilometers wide. The modeled fault dips upward through the ground at a 60-degree angle, with one side of the fault moving at a slanted angle horizontally and vertically 10 centimeters relative to the other side. The model estimated the maximum displacement of Earth's surface from the quake at approximately 1 centimeter, which is at the threshold of what is detectable with UAVSAR. The region of ground displacement is indicated by the darker blue area located in the right center of the image.

In November 2008, NASA JPL scientists began conducting a series of UAVSAR flights over regions of Northern and Southern California that are actively deforming and are marked by frequent earthquakes. About every six months, the scientists precisely repeat the same flight paths to produce images of ground deformation called interferograms. From these data, 3-D maps are being created for regions of interest, including the San Andreas and other California faults, extending from the Gulf of California in Mexico to Santa Rosa in the northern San Francisco Bay.

UAVSAR, which flies on a NASA C20-A III aircraft from NASA's Armstrong Flight Research Center, measures ground deformation over large areas to a precision of 0.1 to 0.5 centimeters (0.04 to 0.2 inches).

By comparing the repeat-pass radar observations, scientists hope to measure any crustal deformations that may occur between observations, allowing them to 'see' the amount of strain building up on fault lines, and giving them a clearer picture of which faults are active and at what rates they're moving, both before earthquakes and after them. The UAVSAR fault mapping project is designed to substantially improve knowledge of regional earthquake hazards in California. The 3-D UAVSAR data will allow scientists to bring entire faults into focus, allowing them to understand faults not just at their surfaces, but also at depth. When integrated into computer models, the data should give scientists a much clearer picture of California's complex fault systems.

The scientists are estimating the total displacement occurring in each region. As additional observations are collected, they expect to be able to determine how strain is partitioned between individual faults.

The UAVSAR flights serve as a baseline for pre-earthquake activity. As earthquakes occur during the course of this project, the team is measuring the deformation at the time of the earthquakes to determine the distribution of slip on the faults, and then monitoring longer-term motions after the earthquakes to learn more about fault zone properties.

Airborne UAVSAR mapping can allow a rapid response after an earthquake to determine what fault was the source and which parts of the fault slipped during the earthquake. Information about the earthquake source can be used to estimate what areas were most affected by the earthquake shaking to guide rescue and damage assessment response.

The scientists now plan to acquire UAVSAR data from the region, possibly as soon as this week, and process the data to validate and improve the results of their model.

Image credit: NASA/JPL-Caltech/USGS/Google Earth

Note: For more information, see NASA Model Provides a 3-D Look at L.A.-area Quake.

Sinkholes Predicted in Louisiana

Analyses by NASA's UAVSAR radar performed after the Bayou Corne, Louisiana, sinkhole formed show it was able to detect precursory ground surface movement of up to 10.2 inches (260 millimeters) more than a month before the sinkhole collapsed in August 2012. This interferogram was formed with images acquired on June 23, 2011 and July 2, 2012. Colors represent surface movement, with one full color wrap corresponding to 4.7 inches (120 millimeters) of displacement.

Image credit: NASA/JPL-Caltech

Note: For more information, see That Sinking Feeling.

Hofsjökull Ice Cap, Iceland

This image shows a small part of the Hofsjökull ice cap in Iceland, which encompasses several glaciers. The fan at upper left is part of a glacier called Mûlajökul.

The above map shows the flight path (red lines) for a single flight to map flow speeds across two ice caps with the UAVSAR instrument. Each five-hour flight will follow this same complicated path for optimal coverage. The ice caps appear in white in the center of the tangled flight lines; Langjökull is west (left) of Hofsjökull. Keflavik International Airport is on the peninsula in the southwest.

A high-precision radar instrument from NASA's Jet Propulsion Laboratory, Pasadena, California, left Southern California for Iceland today to create detailed maps of how glaciers move in the dead of winter. This will help scientists better understand some of the most basic processes involved in melting glaciers, which are major contributors to rising sea levels.

Photo and map credit: Caltech

Note: For more information, see NASA Radar Maps the Winter Pace of Iceland's Glaciers.

Galeras Volcano, Colombia

This false-color image of Colombia's Galeras Volcano, was acquired by UAVSAR on March 13, 2013. A highly active volcano, Galeras features a breached caldera and an active cone that produces numerous small to moderate explosive eruptions. It is located immediately west of the city of Pasto. UAVSAR will precisely fly the same flight path over the volcano in 2014. By comparing these camera-like images taken at different times, interferograms are generated that reveal changes in Earth's surface caused by volcanic deformation.

UAVSAR is part of NASA's ongoing effort to apply space-based technologies, ground-based techniques and complex computer models to advance our understanding of Earth deformation processes, such as those caused by earthquakes, volcanoes and landslides. UAVSAR is also serving as a flying test bed to evaluate the tools and technologies for future space-based radars, such as those planned for a NASA Synthetic Aperture Radar (SAR) mission currently in formulation. That mission will study hazards such as earthquakes, volcanoes and landslides, as well as global environmental change.

Image credit: NASA/JPL-Caltech

Napo River in Ecuador and Peru

On March 17, 2013, NASA’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) acquired synthetic aperture radar data over the Napo River in Ecuador and Peru. The image colors indicate the likelihood of inundation (flooding) beneath the forest canopy, which is difficult to determine using traditional optical sensors. Red and yellow shades indicate a high likelihood of standing water with emergent vegetation, blue and green shades are areas less likely to be inundated, and black indicates the open water areas of the Napo River. These data, which have already been transmitted to a field team working along the Napo River, will be used to guide field measurements during a second observation by UAVSAR on March 31, 2013. The image is a 8.7-mile-wide by 5.6-mile-long (14-kilometer-wide by 9-kilometer-long) segment of an image measuring more than 124 miles (200 kilometers) long. North is toward the upper right. The resolution is 20 feet (6 meters). UAVSAR data like these are helping scientists assess the effectiveness of using synthetic aperture radar data to study the inundation dynamics of this and similar rivers around the world.

Image credit: NASA/JPL-Caltech

Note: For more information, see NASA Flies Radar South on Wide-Ranging Expedition; also, PIA16942: NASA Sends Unmanned Aircraft To Study Volcanoes and Wetlands.