ALBERT

Description: We present a new, S-velocity model of the European upper mantle, constrained by inversions of seismic waveforms from broad-band stations in Europe and surrounding regions. We collected seismograms for the years 1990–2007 from all permanent stations in Europe for which data were available. In addition, we incorporated data from temporary experiments. Automated multimode inversion of surface and S-wave forms was applied to extract structural information from the seismograms, in the form of linear equations with uncorrelated uncertainties. The equations were then solved for seismic velocity perturbations in the crust and mantle with respect to a 3-D reference model with a realistic crust. We present two versions of the model: one for the entire European upper mantle and another, with the highest resolution, focused on the upper 200 km of the mantle beneath western and central Europe and the circum Mediterranean. The mantle lithosphere and asthenosphere are well resolved by both models. Major features of the lithosphere–asthenosphere system in Europe and the Mediterranean are indentified. The highest velocities in the mantle lithosphere of the East European Craton (EEC) are found at about 150 km depth. There are no indications for a deep cratonic root below about 330 km depth. Lateral variations within the cratonic mantle lithosphere are resolved as well. The locations of kimberlites correlate with reduced S-wave velocities in the shallow cratonic mantle lithosphere. This anomaly is present in regions of both Proterozoic and Archean crust, pointing to an alteration of the mantle lithosphere after the formation of the craton. Strong lateral changes in S-wave velocity are found at the northwestern margin of the EEC and may indicate erosion of cratonic mantle lithosphere beneath the Scandes by hot asthenosphere. The mantle lithosphere beneath western Europe and between the Tornquist–Teisseyre Zone and the Elbe Line shows moderately high velocities and is of an intermediate character, between cratonic lithosphere and the thin lithosphere of central Europe. In central Europe, Caledonian and Variscian sutures are not associated with strong lateral changes in the lithosphere–asthenosphere system. Cenozoic anorogenic intraplate volcanism in central Europe and the circum Mediterranean is found in regions of shallow asthenosphere and close to changes in the depth of the lithosphere–asthenosphere boundary. Very low velocities at shallow upper-mantle depths are present from eastern Turkey towards the Dead Sea transform fault system and Sinai, beneath locations of recent volcanism. Low-velocity anomalies extending vertically from shallow upper mantle down to the transition zone are found beneath the Massif Central, Sinai and the Dead Sea, the Canary Islands and Iceland.

Description: The time has come to exploit the full richness of broadband, three-component waveforms. The inversion of full seismograms leads to a tremendous improvement in imaging resolution due to the ability to map structures that are smaller than the seismic wavelength. In addition, it provides important constraints on density and attenuation. State-of-the-art software for full waveform tomography is available in scientific environments but is not yet accessible to the practitioner. The Toolbox for Applied Seismic Tomography (TOAST) will open a new window to seismic inversion. Due to advances in available computational resources and recent developments in high performance and parallelized computing, 3D inversion of full seismograms is within reach. By combining tested code collections for waveform modelling and the solution of large inverse problems, complemented by experience in the management of large software projects and by sound expertise in the inversion of elastic waves from the centimeter to the kilometer scale, the cooperation of the TOAST project partners will provide a unique knowledge base for implementing flexible and efficient tools for full waveform tomography and to transfer the knowledge to industrial practice. The TOAST project pursues the concept of modularization. It will provide modules that interact through standardized interfaces and thereby can be re-combined in application-specific and efficient ways. The Toolbox for Applied Seismic Tomography will prove its worth through application to surveys from commercial practice. Existing data from seismic experiments at different scales (e.g., monitoring of embankments, CO2 sequestration studies) and newly aquired shallow seismic and ultrasonic data will serve as case studies to validate the functionality of the toolbox.

Description: An instantaneous measure of the moment magnitude (Mw) of an ongoing earthquake is estimated from the moment rate function (MRF) determined in real-time from available seismic data using waveform inversion. Integration of the MRF gives the moment function from which an instantaneousMw is derived. By repeating the inversion procedure at regular intervals while seismic data are coming in we can monitor the evolution of seismic moment and Mw with time. The final size and duration of a strong earthquake can be obtained within 12 to 15 minutes after the origin time. We show examples of Mw monitoring for three large earthquakes at regional distances. The estimated Mw is only weakly sensitive to changes in the assumed source parameters. Depending on the availability of seismic stations close to the epicenter, a rapid estimation of the Mw as a prerequisite for the assessment of earthquake damage potential appears to be feasible.