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Glacial retreat in recent decades has exposed unstable slopes and allowed deep water to extend beneath some of those slopes. Slope failure at the terminus of Tyndall Glacier on 17 October 2015 sent 180 million tons of rock into Taan Fiord, Alaska. The resulting tsunami reached elevations as high as 193 m, one of the highest tsunami runups ever documented worldwide. Precursory deformation began decades before failure, and the event left a distinct sedimentary record, showing that geologic evidence can help understand past occurrences of similar events, and might provide forewarning. The event was detected within hours through automated seismological techniques, which also estimated the mass and direction of the slide - all of which were later confirmed by remote sensing. Our field observations provide a benchmark for modeling landslide and tsunami hazards. Inverse and forward modeling can provide the framework of a detailed understanding of the geologic and hazards implications of similar events. Our results call attention to an indirect effect of climate change that is increasing the frequency and magnitude of natural hazards near glaciated mountains.

Glacial retreat in recent decades has exposed unstable slopes and allowed deep water to extend beneath some of those slopes. Slope failure at the terminus of Tyndall Glacier on 17 October 2015 sent 180 million tons of rock into Taan Fiord, Alaska. The resulting tsunami reached elevations as high as 193 m, one of the highest tsunami runups ever documented worldwide. Precursory deformation began decades before failure, and the event left a distinct sedimentary record, showing that geologic evidence can help understand past occurrences of similar events, and might provide forewarning. The event was detected within hours through automated seismological techniques, which also estimated the mass and direction of the slide - all of which were later confirmed by remote sensing. Our field observations provide a benchmark for modeling landslide and tsunami hazards. Inverse and forward modeling can provide the framework of a detailed understanding of the geologic and hazards implications of similar events. Our results call attention to an indirect effect of climate change that is increasing the frequency and magnitude of natural hazards near glaciated mountains.

Reconciliation of structures shown in global models of Earth structure with those shown in detailed, high-resolution regional models has become one of the most important tasks in seismic tomography. Recent studies have shown that combination of regional seismic phases with teleseismic phases can greatly increase location accuracy; however, for this to be the case, the velocity structure has to be well resolved on a fine scale. The most efficient method to accomplish this task is development of multi-resolution models using local (but smooth) basis functions that increase in resolution from regions with sparse data coverage to regions of dense coverage. This paper reports on recent results from an ongoing project designed to bridge the gap between regional and global seismic tomography and achieve correspondingly incremental improvements in event location. We have previously developed a moderately high-resolution global model (equivalent to spherical harmonic degree 18) using local spline functions. This model improves locations using teleseismic phases over other more finely parameterized models ( Antolik et al., 2001). Here we extend the same techniques to simultaneous development of more detailed regional models for inclusion within the global model. We describe progress in constructing a new regional model of the Africa/Mediterranean region which makes use of surface wave dispersion data, regional travel times and waveforms, and teleseismic phase arrivals. This model also incorporates shear wave anisotropy and agrees well with other published models for the region. Other regions for which we intend to develop combined regional/global models include the former Soviet Union and North America. Tomographic models can also be vastly improved through the use of sources with calibrated travel-time data (i.e., reference events with accurately known locations)., Presented at the Seismic Research Review: Worldwide Monitoring of Nuclear Explosions (23rd) held in Jackson Hole, WY on 2-5 October 2001. Published in the Proceedings of the Seismic Research Review: Worldwide Monitoring of Nuclear Explosions, p136-146, 2001.

The objective of the project is to develop and improve upon three-dimensional (3-D) seismic velocity models of the Earth and to utilize such models for improving the locations of events recorded at regional and teleseismic distances. Our previous experiments performed using 3-D models of varying resolution show that the accuracy of event location with respect to ground truth does not necessarily improve with an increasing number of free parameters in a model. One reason for this may be the lack of waveform data used for constructing recent high-resolution models, since the maximum sensitivity of seismic travel times to structure is in the middle to lower mantle. In this paper we develop a new joint, P and S velocity model parameterized in terms of radial and horizontal cubic splines, using a combination of direct and differential travel times and surface wave phase measurements. The accuracy of the travel time data has been improved by relocating the events using a previously existing 3-D mantle P wave model. The cubic spline parameterization conveniently allows more detailed models to be inserted within it for use of regional phases in event location. Our preliminary model shows substantial differences in compressional velocity in the uppermost mantle compared with previous models. In conjunction with the model development, we are collecting new reference events with accurate locations, among them earthquakes on mid-ocean ridges and transforms, using a constrained inversion technique., Proceedings of the Annual DoD/DOE Seismic Research Symposium (22nd): Planning for Verification of and Compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) held in New Orleans, Louisiana on 13-15 September 2000. U.S. Government or Federal Rights. The original document contains color images.

The primary objective of this work has been to map the variations of elastic mantle properties beneath Eurasia over horizontal length scales of approximately 1000-1500 kilometers and vertial length scales of 50-100 kilometers in the upper mantle. Large and diverse datasets of seismic waveforms, absolute and relative body wave travel times, and surface wave phase velocity and amplitudes have been collected and have been analyzed. Several tens of thousands of measurements of intermediate period surface wave dispersion have been made in order to characterize and properly account for the highly heterogeneous velocity structure associated with the crust and the uppermost mantle. Global maps of phase velocity for Love and Rayleigh waves in the period range 35-150 seconds have been produced. The new dataset of surface wave dispersion has been combined with previously collected data in the finalization of a new 3-D whole mantle model. In comparison with previous Harvard mantle models the horizontal resolution has been increased by expanding the global structure up to spherical harmonic degree l = 20, and a radial parameterization has been adopted which gives better vertical resolution in the upper mantle.