S U M M A R Y History of instrumental seismology is short. Seismograms are available only for a little more than 100 years; high-quality seismograms are available only for the last 50 years and the seismological database is very limited in time. To extend the database, seismograms of old events are of vital importance. Many unusual earthquakes are known to have occurred, but their seismological...

Many geophysical problems involve inverting data in order to obtain meaningful descriptions of the Earth‘s interior. One of the basic characteristics of these inverse problems is their non-uniqueness. Since computation power has increased enormously in the last few years, it has become possible to deal with this non-uniqueness by generating and selecting a number of models that all fit the data...

The inclusion of amplitude constraints in body-wave inversions allows the separation of earth models which seem indistinguishable on the basis of traveltime observations. Amplitude constraints can be included through the calculation of synthetic seismograms by the quantized ray theory formulation. As an example, a preliminary model for the velocity structure of the upper mantle beneath part of ...

In our last SEP report, we introduced an AVO dataset consisting of seismic, petrophysical and well-log information which was provided by Mobil as part of an AVO workshop (?). The prestack seismic data are heavily contaminated by free-surface and water-bottom multiple reflections, and thus represent a challenge for true-amplitude processing. We described our preliminary preprocessing work and di...

Earthquakes in subduction zones occur the slab mantle, subducting crust, on plate interface, and, some cases, mantle wedge–regions that are separated by strong seismic discontinuities. These discontinuities typically imaged with techniques using teleseismic waves, while local earthquakes located based arrival times. While this combination of imaging and earthquake location provides a good initi...

Seismic wave propagation simulations are limited in their frequency content by two main factors: (1) the resolution of the seismic wave-speed structure of the region in which the seismic waves are propagated through and (2) the extent of our understanding about the rupture process, mainly on the short length scales. For this reason, high-frequency content in the ground motion must be simulated ...