International audienceGeophysical observations from the 2011 moment magnitude (Mw) 9.0 Tohoku-Oki, Japan earthquake allow exploration of a rare large event along a subduction megathrust. Models for this event indicate that the distribution of coseismic fault slip exceeded 50 meters in places. Sources of high-frequency seismic waves delineate the edges of the deepest portions of coseismic slip and do not simply correlate with the locations of peak slip. Relative to the Mw 8.8 2010 Maule, Chile earthquake, the Tohoku-Oki earthquake was deficient in high-frequency seismic radiation--a difference that we attribute to its relatively shallow depth. Estimates of total fault slip and surface secular strain accumulation on millennial time scales suggest the need to consider the potential for a future large earthquake just south of this event
The Watershed Allied Telemetry Experimental Research (WATER) is a simultaneous airborne, satellite‐borne, and ground‐based remote sensing experiment aiming to improve the observability, understanding, and predictability of hydrological and related ecological processes at a catchment scale. WATER consists of the cold region, forest, and arid region hydrological experiments as well as a hydrometeorology experiment and took place in the Heihe River Basin, a typical inland river basin in the northwest of China. The field campaigns have been completed, with an intensive observation period lasting from 7 March to 12 April, from 15 May to 22 July, and from 23 August to 5 September 2008: in total, 120 days. Twenty‐five airborne missions were flown. Airborne sensors including microwave radiometers at L, K, and Ka bands, imaging spectrometer, thermal imager, CCD, and lidar were used. Various satellite data were collected. Ground measurements were carried out at four scales, that is, key experimental area, foci experimental area, experiment site, and elementary sampling plot, using ground‐based remote sensing instruments, densified network of automatic meteorological stations, flux towers, and hydrological stations. On the basis of these measurements, the remote sensing retrieval models and algorithms of water cycle variables are to be developed or improved, and a catchment‐scale land/hydrological data assimilation system is being developed. This paper reviews the background, scientific objectives, experiment design, filed campaign implementation, and current status of WATER. The analysis of the data will continue over the next 2 years, and limited revisits to the field are anticipated.
[1] A recent prospective on the Yellowstone Caldera discounts its explosive potential based on inferences from tomographic studies which suggests a high degree of crystallization of the underlying magma body. In this study, we show that many of the first teleseismic P-wave arrivals observed at seismic stations on the edge of the caldera did not travel through the magma body but have taken longer but faster paths around the edge. After applying a number of waveform modeling tools, we obtain much lower seismic velocities than previous studies, 2.3 km/sec (V p ) and 1.1 km/sec (V s ). We estimate the physical state of the magma body by assuming a fluid-saturated porous material consisting of granite and a mixture of rhyolite melt and water and CO 2 at a temperature of 800°C and pressure at 5 km (0.1 GPa). We found that this relatively shallow magma body has a volume of over 4,300 km 3 and is about 32% melt saturated with about 8% water plus CO 2 by volume.
Waveform ModelingBefore we can model the P waveform data of the Virginia earthquake, we need to determine the source parameters. Our preferred method is the Cut-And-Paste (CAP) method 1 , which allows the source parameters to be estimated in the presence of crustal complexity. This technique fits P nl and surface wave segments between observed and synthetics that are allowed to shift independently in timing for alignment (Fig. S1). The earthquake is assumed to be a sheardislocation with three parameters; strike, dip, and rake. We search for the best-fitting set of parameters as a function of earthquake depth through a grid-search approach 1 (Fig. S1b). During this search, each segment of waveforms is allowed to shift some time to compensate their traveltime residuals generated by heterogeneities in regional crustal structures. The amplitudes are on the same scale except that P nl 's are amplified by a factor of 2. Station names and distance are indicated for each station.Generally, cratons are relatively homogeneous compared to tectonic regions and the shifts are small and the cross-correlation coefficients, numbers below each trace, are high 2 . Note that Hidden hotspot track beneath the eastern United States SUPPLEMENTARY INFORMATION
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