Publications

HypoDD is a Fortran computer program package for relocating earthquakes with the double-difference algorithm of Waldhauser and Ellsworth (2000). This document provides a brief introduction into how to run and use the programs ph2dt and hypoDD to compute double-difference (DD) hypocenter locations. It gives a short overview of the DD technique, discusses the data preprocessing using ph2dt...

We have examined the local base of the south polar layered deposits (SPLD) exposed in the bounding scarp near 72°–74°S, 215°–230°W where there is a clear unconformable contact with older units. Sections of layering up to a kilometer thick were examined along the bounding scarp, permitting an estimate of the thinnest individual layers yet reported in the SPLD. Rhythmic layering is also...

No abstract available.

No abstract available.

The Los Angeles Region Seismic Experiment (LARSE) is a joint project of the U.S. Geological Survey (USGS) and the Southern California Earthquake Center (SCEC). The purpose of this project is to produce seismic images of the subsurface of the Los Angeles region down to the depths at which earthquakes occur, and deeper, in order to remedy a deficit in our knowledge of the deep structure of...

We use the energy-to-moment ratio, as introduced by Newman and Okal [1998] to examine the source characteristics of normal-faulting intraslab earthquakes, compared to nearby interplate thrust events, based on recent case studies in central Chile and southeastern Mexico. In Chile, we find that the 1997 intraslab event had an exceptionally large E/M0 ratio, 30 times greater than the nearby

We examine the various methods and parameters in common use for quantifying and reporting surface topographic "roughness." It is shown that scale-dependent roughness parameters are almost always required, though not widely used. We suggest a method of standardizing the parameters that are computed and reported so that topographic data gathered by different workers using different field...

Approximately half the Nation's original wetland habitats have been lost over the past 200 years. In part, this has been a result of natural evolutionary processes, but human activities, such as dredging wetlands for canals or draining and filling for agriculture, grazing, or development, share a large part of the responsibility for marsh habitat alteration and destruction. Louisiana's...

In the past decade, Earth scientists have recognized the seismic hazards that crustal faults and sedimentary basins pose to Seattle, Washington (Figure 1). In 1998, the US. Geological Survey and its collaborators initiated a series of urban seismic studies of the upper crust to better map seismogenic structures and sedimentary basins in the Puget Lowland. These studies are called the...

At a marsh on the hanging wall of the Seattle fault, fossil brackish water diatom and plant seed assemblages show that the marsh lay near sea level between ∼7500 and 1000 cal yr B.P. This marsh is uniquely situated for recording environmental changes associated with past earthquakes on the Seattle fault. Since 7500 cal yr B.P., changes in fossil diatoms and seeds record several rapid...

In 1946, 1960, and 1964, major tsunamis (giant sea waves usually caused by earthquakes or submarine landslides) struck coastal areas of the Pacific Ocean. In the U.S. alone, these tsunamis killed hundreds of people and caused many tens of millions of dollars in damage. Recent events in Papua New Guinea (1998) and elsewhere are reminders that a catastrophic tsunami could strike U.S...

No abstract available.