AGU Journal Highlights -- March 19, 2008

Title: Full waveform inversion of reflection seismic data for ocean temperature profiles

Authors: Warren T. Wood: Naval Research Laboratory, Stennis Space Center, Mississippi, U.S.A.;

W. Steven Holbrook: Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming, U.S.A.;

Mrinal K. Sen and Paul L. Stoffa: Institute for Geophysics, University of Texas at Austin, Austin, Texas, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL032359, 2008; http://dx.doi.org/10.1029/2007GL032359

5. Tracking earthquake motion with GPS at finer timescales

After a large earthquake, a fault continues to creep aseismically, resulting in measurable ground deformation. Typically, such postseismic motions are measured with Global Positioning System (GPS) receivers. In order to reduce intrinsic GPS noise for these studies, most scientists average all GPS data collected within 24-hour spans. Miyazaki and Larson note that these 24-hour averages make it impossible to separate seismic deformations from the initial aseismic deformations. They study the 2003 Tokachi-Oki event, where the ground signal was further complicated by the rupture of a large aftershock (magnitude 7.4) about an hour after the main shock (magnitude 8). By reducing GPS noise, the authors estimate the displacements due to both earthquakes, along with aseismic motions in the first few hours. By inverting the measurements of surface deformation, they find that slip between the two earthquakes occurred between the two epicentral regions, possibly triggering the aftershock. The authors expect that higher sampling rates for GPS solutions will help scientists gain greater insight into studies of slip propagation and stress transfer.

Title: Coseismic and early postseismic slip for the 2003 Tokachi-Oki earthquake sequence inferred from GPS data

Authors: Shin'ichi Miyazaki: Earthquake Research Institute, University of Tokyo, Tokyo Japan;

Kristine M. Larson: Department of Aerospace Engineering Sciences, University of Colorado, Boulder, Colorado, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL032309, 2008; http://dx.doi.org/10.1029/2007GL032309

6. Atlantic sea-surface temperatures affect Indian monsoon

The Indian monsoon is strongly influenced by El Niño–Southern Oscillation (ENSO) patterns on interannual timescales, with a drier than normal monsoon season usually preceding peak El Niño conditions and a wetter than normal monsoon season preceding peak La Niña conditions. However, sea surface temperatures (SST) in the Pacific, which serve as an indicator of the phase of the ENSO cycle, are not the only factors affecting Indian monsoon patterns. Building on their recent discovery that atmospheric teleconnections between the tropical Atlantic Ocean and the Indian basin contributed to the weakening of the ENSO-monsoon link during the 1980s and 1990s, Kucharski et al. investigate the role of south equatorial Atlantic SSTs in forcing the volume and pattern of Indian monsoon rainfall. Using two observational data sets and two ensembles of models, the authors show that characteristics of Indian monsoon rainfall are significantly correlated with south equatorial Atlantic SSTs. The authors expect that their results might help with monsoon forecast efforts.