Thursday, May 4, 2023, 16:00
WHGA Auditorium
Andreas Fichtner, ETHZ
Abstract:
Seismic tomography is the art and science of translating recordings of
seismic waves into quantitative images of the Earth's interior.
Conceptualised around 50 years ago, the family of seismic tomography
methods has grown and diversified rapidly, thereby evolving into one of
the cornerstones of geoscience. Seismic tomography reveals the dynamics
and composition of the Earth and other planetary bodies, illuminates the
structure of active volcanoes and fault zones, provides information on
deep reservoirs and storage sites, and enables the accurate simulation
of earthquake-induced ground motion in densely populated sedimentary
basins.
The propagation of seismic waves through the Earth is governed by the
wave equation, a second-order linear PDE. Its scale invariance permits
the translation of tomographic techniques between seismology (10,000 km
scale) and medical ultrasound (10 cm scale). In this presentation, we
will focus on a recently developed tomographic technique, commonly known
as full-waveform inversion (FWI). The exploitation of complete wavefield
recordings, enables FWI to produce images with unprecedented resolution,
thereby producing valuable insight, not only in seismology. Following an
introduction to the foundations of FWI from a seismological perspective,
we will present two applications in medical ultrasound that are both
motivated by early-stage cancer detection: (1) the imaging of a complete
mouse as a proof of concept, and (2) the imaging of the human brain
through the skull.