The simultaneous inversion for hypocentre locations and 3-D seismic velocity structure is known as local earthquake tomography (LET e.g. Furthermore, due to the CSS source–receiver geometry in combination with the inherent nature of seismic wave energy being preferably transmitted by high-velocity low-attenuation rock volumes, CSS-derived seismic models exhibit a tendency towards the higher velocities, while smaller low-velocity zones remain unsampled ( Kissling 1993). Due to the setup of CSS methods (source–receiver geometry) and considering the resulting ray paths, however, which are often more or less parallel to each other, information obtained on seismic velocities is limited. Using the information from several crossing 2-D seismic profiles the 2-D (in-line) migration can be further constrained and subsequently allows a 3-D (off-line) migration of the reflector elements (e.g. This process is called 2-D (in-line) migration and is routinely applied along 2-D seismic profiles. Knowing the seismic velocities, it is possible to determine depth, and approximate location and dip of a reflecting/refracting element. This leads to an imaging geometry with sources and receivers on the same side of the studied volume. Controlled sources are either at or close to the Earth's surface. On the crustal scale, CSS methods are 2-D techniques applied to 3-D structures. CSS methods are especially suitable for detecting and imaging seismic interfaces showing a strong contrast in seismic velocity, such as the crust-mantle boundary (Moho). They have provided a wealth of information on crustal structure worldwide, and, in particular, on the crustal structure of the Alpine region (e.g. Refraction and reflection seismology, both controlled-source seismology (CSS) methods, are complementary high-resolution imaging techniques (e.g. Furthermore, our new 3-D crustal model directly includes a 3-D migrated image of the Ivrea body.Ĭontrolled-source seismology, Seismic tomography, Crustal structure, Europe 1 Introduction Due to the larger number of available Moho reflector elements a more accurate definition of plate boundaries at Moho level is possible and, therefore, new insights in deep lithosphere structures of the Alpine collision zone can be expected. The biggest differences occur along plate boundaries, where the strong lateral velocity variations are best resolved by LET. In general, it is in a good agreement with previous studies. Our model clearly shows three Moho surfaces, being Europe, Adria and Liguria as well as major tectonic structures like suture zones and the high-velocity Ivrea body. Finally, our definition of LET Moho elements and their uncertainties is validated by comparisons of highest quality Moho results from both methods coinciding in 353 localities. These uncertainty estimates are based on values of the diagonal element of the resolution matrix, absolute P-wave velocities that are typical for crust and mantle and a specific velocity gradient across the Moho discontinuity. The consistent combination of results from the two different seismic methods is feasible due to LET Moho elements, as defined by characteristic P-wave velocities and their uncertainty estimates. Our western Alpine 3-D model is primarily based on a well-defined Moho, constrained by CSS and LET data, and includes smooth lateral variations in seismic velocities mainly constrained by LET data, but locally also by CSS data. Our approach combines either data by taking into account the strengths of the individual seismic methods. Several quizzes, as well as 3 mini-projects, will allow you to check your knowledge and assess your understanding of the various topics.We present a newly developed approach of combining controlled-source seismology (CSS) and local earthquake tomography (LET) data to obtain a new 3-D crustal model of the western Alpine region. magnet-Earth, seismicity of Mars, seismic sensors, probabilistic approaches). Various types of sessions are proposed: regular sessions describing a phenomenon or explaining its basic principles, lab sessions illustrating concepts through simple experiments (fault motion, liquefaction, resonant column tests, shaking table tests) and research topics focusing on advanced topics from various research fields (e.g.
It investigates various technical fields: rock mechanics, soil dynamics, structural dynamics and dynamic soil-structure interaction. It is consequently aimed at undergraduates, graduates and professionals interested in engineering seismology, earthquake engineering or seismic risk. This course ranges from the earth structure, the generation of earthquakes and seismic waves by faults to the seismic response of soils, foundations and structures as well as seismic risk.
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