Andreas Fichtner on the Frontiers of Seismic Imaging
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In the podcast, Andreas Fichtner describes the state of the art in seismic imaging. Despite enormous improvements in our capabilities over the past decades, there are still many structures and data types that remain elusive. Fichtner explains the various types of challenges faced by researchers seeking to sharpen our images of the Earth’s interior from seismic data. While some challenges appear insurmountable, others are gradually yielding to improved methods and computational power, and we can expect to see continual improvements over the next decade.
Fichtner is a Professor in the Department of Earth and Planetary Sciences at the Federal Institute of Technology in Zurich.
Numerical simulation of the L’Aquila earthquake of April 6, 2009
Then umerical simulation shows surface waves that propagate along the Earth’s surface and body waves that propagate through the interior.
As Fichtner explained in the podcast, although the absolute size of the resolvable structures is much smaller in the case of medical ultrasound, the relative resolution of seismic images is better than that of ultrasound.
Seismic recording of the Tohoku earthquake of that struck on March 11, 2011. The recording was made at the Black Forest Observatory in Germany, 83.3 degrees of latitude west of the earthquake epicenter. The body waves arrive first as they travel faster than the surface waves.
Each wave travels along a different path through the earth, and therefore “sees” as different part of the Earth. In the diagram, the simulated earthquake is at left, and the P waves was shown in red and S wave in green.
Brian Kennett
Section of a seismic tomographic image at depth of 100 km. The continents have fast seismic speeds (blue) with the exception of their active margins. Mid-ocean ridges are characterized by low velocities (red).
Section of a seismic tomographic image at depth of 2,800 km. The blue areas (fast seismic wave speed) may be accumulations of colder subducted material. The large red areas are the large low shear-velocity provinces (LLSVPs) discussed in earlier podcasts, such as the one with Alan McNamara.