AGU Journal Highlights -- Aug. 14, 2007

Authors: Neven S. Fučkar: Atmospheric and Oceanic Sciences Program, Princeton University, Princeton, New Jersey, U.S.A.;

Geoffrey K. Vallis: Geophysical Fluid Dynamics Laboratory, National Oceanic and Atmospheric Administration, Princeton, New Jersey, U.S.A.; also at Atmospheric and Oceanic Sciences Program, Princeton University, Princeton, New Jersey, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL030379, 2007

5. Estimating local tsunami wave height from great earthquakes

The massive 9.2-magnitude Sumatra-Andaman earthquake on 26 December 2004 generated a tsunami that propagated throughout the Indian Ocean, killing more than 250,000 people. By contrast, the nearby 8.7-magnitude Simeulue-Nias earthquake on 28 March 2005 generated a small tsunami that caused only a few casualties. Though these earthquakes occurred in similar tectonic settings, their tsunami were markedly different, highlighting the need for reliably determining tsunami hazards from earthquake geometry. Using geodetic and stress accumulation studies, McCloskey et al. model about 100 different complex earthquake ruptures in this area and calculate their sea-floor displacements and resulting tsunami wave heights. They find that, for locations close to the earthquake source, the timing of tsunami inundation is independent of the earthquake magnitude and slip distribution. However, the maximum tsunami wave height is directly proportional to the vertical displacement of the rupture. Because stress field studies indicate that the Sumatra-Andaman region is overdue for another great earthquake, the authors note that a single estimate of vertical displacement during an earthquake might provide a reliable short-term forecast of tsunami wave height.

Title: Near-field propagation of tsunamis from megathrust earthquakes

Authors: John McCloskey, Andrea Antonioli, Sandy Steacy, Suleyman S. Nalbant, JianDong Huang, and Paul Dunlop: Geophysics Research Group, School of Environmental Sciences, University of Ulster, Coleraine, Northern Ireland, U.K.;

Alessio Piatanesi, Massimo Cocco, and Carlo Giunchi: Seismology and Tectonophysics Department, Istituto Nazionale de Geofisica e Vulcanologia, Rome, Italy;

Kerry Sieh: Tectonics Observatory, California Institute of Technology, Pasadena, California, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL030494, 2007

6. Soil moisture induces atmospheric circulation: Observations from Africa's Sahel

Theoretical studies and models have shown that contrasting land-surface properties can induce circulations in the atmosphere. Taylor et al. seek to observe this through monitoring Africa's Sahel region, an area where intense precipitation generates a varied spatial and temporal distribution of soil moisture. Using aircraft and satellite data, the authors find that the air just above wet soil was moister and up to 3ºC (5 ºF) cooler than nearby dry areas. In addition, winds near the ground were found to vary significantly over patches of wet soil as small as 10 kilometers (6 miles) across, consistent with the theory that soil moisture can drive atmospheric circulations. The authors expect that analysis of additional cloud data will reveal the role of these circulations in the generation of new storms, aiding forecasting in this notoriously unpredictable region and helping to refine models of tropical climate.