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Scripps contact: Mario Aguilera (858-245-3175) or AGU Press Room Scripps Communications: 858-534-3624, scrippsnews@ucsd.edu

Scripps News at 2015 AGU Fall Meeting Scripps Institution of Oceanography/University of California, San Diego Earthquake Swarms and the Big One S11A-2748 • Monday, Dec. 14, 8 a.m. – 12:20 p.m. • Moscone South Poster Hall  Are earthquake swarms a prelude to the Big One? Scripps Institution of Oceanography at UC San Diego researchers will present their analysis of earthquake swarms across Southern California to see if these localized groups of temblors have a distinct pattern. The findings can help produce more realistic estimates of earthquake probabilities in regions prone to swarms.

Former Scripps postdoctoral student Qiong Zhang and Scripps geophysicist Peter Shearer analyzed 296 earthquake swarms since 1981 and found that they are most common in the Salton Sea and Coso geothermal areas. They are also numerous at the northern and southern ends of the 130-mile long San Jacinto Fault, a major fault in California located about 60 miles northeast of San Diego and the most seismically active fault zone in the region. Earthquake swarms cause concern because of the uncertainty as to whether

they are likely to lead to the next Big One. Since they cause lower-than-average stress drops before and after a quake than other tremors in Southern California, the researchers suggest swarms may be associated with extensional stress in the crust caused by rocks stretching apart.  PRESENTATION TITLE: “IDENTIFICATION AND CHARACTERIZATION OF EARTHQUAKE SWARMS IN SOUTHERN CALIFORNIA”

Google Maps image of earthquake swarms in the Salton Sea in 2009. Credit: The ANZA Seismic Network  

Variability and Trends in Santa Ana Winds, the “Devil’s Breath” A32G-03 • Wednesday, Dec. 16, 10:50 a.m. • Moscone West 3008 Scripps Institution of Oceanography at UC San Diego researchers will present a new study on Santa Ana wind variability over the last six decades, revealing an increase in intensity and sensitivity of Santa Ana wind activity associated with El Niño events. “Santa Anas” are dry, offshore winds that typically occur in fall and winter in Southern California and are often associated with increased wildfire activity. Scripps graduate student Janin Guzman-Morales and Scripps researcher Alexander Gershunov created and analyzed a regional record of Santa Ana winds dating back to 1948, the longest such record to date. The study found that the most extreme Santa Ana wind seasons occur when El Niño is associated with warmer ocean temperatures in the North Pacific Ocean, known as a positive Pacific Decadal Oscillation phase (PDO). After 15 years in a cool phase, the North Pacific recently entered a warm PDO phase. The talk will highlight how variable seasonal Santa Ana wind activity translates to the frequency, duration, and intensity of Santa Ana events from year to year. Nicknamed “devil's breath,” Santa Anas have been known to produce gusts up to 60 mph. PRESENTATION TITLE: “SANTA ANA WINDS OF SOUTHERN CALIFORNIA: THEIR CLIMATOLOGY AND VARIABILITY SPANNING 6.5 DECADES FROM REGIONAL DYNAMICAL MODELING” Earthquake Early Warning System in California S33B-2765 • Wednesday, Dec. 16, 1:40 – 6 p.m. • Moscone South Poster Hall Scripps Institution of Oceanography at UC San Diego geodesist Yehuda Bock will discuss the latest tests in high seismic risk areas in the Western U.S. to further the development of an early warning system for earthquakes and tsunamis. The prototype system developed by Bock and colleagues uses specially designed sensors for the early warning of the arrival of intense seismic waves in populated areas. Bock’s prototype early warning system utilizes MEMS (micro-electromechanical systems) accelerometers developed at Scripps and deployed at existing GPS tracking stations. The ground

A satellite image of Santa Ana winds pushing smoke from widespread wildfires over the Southern California bight. Credit: NASA  

movements that occur as a consequence of the earthquake can be determined in real time, when data from the two instruments are combined. These include the shaking motions that are felt during the earthquake and conventionally measured by seismometers, as well as the permanent shifts in the ground. The system provides a more timely and accurate magnitude estimate for large hazardous earthquakes, especially critical for emergency response and tsunami warning. The presentation will focus on recent testing of the system in two areas with the largest seismic risk in California: along the San Andreas Fault, in the southern segment in proximity to Los Angeles, and the northern section of the Hayward Fault adjacent to San Francisco. In one scenario using a 7.2 magnitude earthquake in northern Baja California in 2010, the prototype system showed a 90-second early warning until the quake was felt in the heavily populated regions of Riverside and Los Angeles Counties.

The system detects the first and non-destructive seismic P-waves to propagate following a tremor to make a rapid calculation and provide an early warning on the impact the following destructive S-waves will have on a region. PRESENTATION TITLE: “PROTOTYPE EARTHQUAKE EARLY WARNING SYSTEM FOR AREAS OF HIGHEST SEISMIC RISK IN THE WESTERN U.S.” Pioneering Green Robotic Technology Conducts Research at Sea IN33C-1810 • Wednesday, Dec. 16, 1:40 – 6 p.m. • Moscone South Poster Hall Scripps Institution of Oceanography at UC San Diego researchers have pioneered a green robotic Wave Glider  technology that harnesses the power of wave and solar energy to conduct research at the seafloor. The wave gliders offer a new approach for conducting long-term seafloor research, including earthquake, tsunami, and nuclear explosion monitoring. Scripps Oceanography Distinguished Professor of Geophysics John Orcutt will discuss recent tests of the technology using one of 120 seafloor seismic/acoustic instruments operated

MEMS accelerator affixed to a GPS tracking station.

The glider and towed acoustic transponder set for a test deployment.

by Scripps for the National Science Foundation and located four kilometers (2.5 miles) deep. The surfboard-size glider, which is powered by rechargeable batteries and solar panels and propelled by wave motion, acts as a data gateway for instruments on the seafloor and satellites in the sky to deliver near-real-time data to researchers. The gliders and seafloor packages have been designed for a two-year operational lifespan at which time the glider swims back to shore from thousands of miles away. If problems arise, another glider can swim out to take the failing glider’s place. “The use of the glider both as a gateway and a system for towing the package to sea over thousands of miles largely eliminates the need for an expensive ship and reduces the costs for making these and many other seafloor measurements,” said Orcutt. PRESENTATION TITLE: “A ROBOTIC COMMUNICATION GATEWAY FOR OCEAN OBSERVATIONS”

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