Bucknell Dance Company Fall 1988

http://digitalcommons.bucknell.edu/dance_performances/1002/thumbnail.jpg

Bucknell Dance Company Spring 1988 Performance

http://digitalcommons.bucknell.edu/dance_performances/1003/thumbnail.jpg

EVALUATION OF THE EVOLVING STRESS FIELD OF THE YELLOWSTONE VOLCANIC PLATEAU FROM 1988 TO 2010 FROM EARTHQUAKE FIRST MOTIONS INVERSION

Within the Yellowstone National Park, Wyoming, the silicic Yellowstone volcanic field is one of the most active volcanic systems all over the world. Although the last rhyolite eruption occurred around 70,000 years ago, Yellowstone is still believed to be volcanically active, due to high hydrothermal and seismic activity. The earthquake data used in this study cover the period of time between 1988 and 2010. Earthquake relocations and a set of 369 well-constrained, double-couple, focal mechanism solutions were computed. Events were grouped according to location and time to investigate trends in faulting. The majority of the events has oblique, normal-faulting solutions. The overall direction of extension throughout the 0.64 Ma Yellowstone caldera looks nearly ENE, consistently with the direction of alignments of volcanic vents within the caldera, but detailed study revealed spatial and temporal variations. Stress-field solutions for different areas and time periods were calculated from earthquake focal mechanism inversion. A well-resolved rotation of σ3 was found, from NNE-SSW near the Hebgen Lake fault zone, to ENE-WSW near Norris Junction. In particular, the σ3 direction changed throughout the years in the Norris Junction area, from being ENE-WSW, as calculated in the study by Waite and Smith (2004), to NNE-SSW, while the other σ3 directions are mostly unchanged over time. The Yellowstone caldera was subject to periods of net uplift and subsidence over the past century, explained in previous studies as caused by expanding or contracting sills, at different depths. Based on the models used to explain these deformation periods, we investigated the relationship between variability in aseismic deformation and seismic activity and faulting styles. Focal mechanisms and P and T axes were divided into temporal and depth intervals, in order to identify spatial or temporal trends in deformation. The presence of “chocolate tablet” structures, with composite dilational faults, was identified in many stages of the deformation history both in the Norris Geyser Basin area and inside the caldera. Strike-slip component movement was found in a depth interval below a contracting sill, indicating the movement of magma towards the caldera.

The Bison: 1988

This digital object was funded in part through a grant from the Andrew W. Mellon Foundation. The digitalization of this object was part of a collaborative effort with the Washington Research Library Consortium and George Washington University.

Dr. Ralph Garber, Canada, President of IASSW 1988 - 1996

A fully revealing portrait of Ralph Garber would require a latter-day Boswell. As ordained, however, an attempt must be made to create a recognizable word picture. And it must give initial attention to the range of influences and factors in Ralph Garber's inheritance and environment that, throughout his life, he experienced, absorbed and utilized in his remarkably creative career.

Jan Floris de Jongh (1910 – 1988), President of IASSW 1954-1961

Jan Floris de Jongh played an undoubtedly significant role in the development of social work within and beyond The Netherlands. Yet, he and his contributions to the field are barely known, particularly in The Netherlands. His achievements warrant much more attention given that this Dutchman was also one of the most relevant figures in the international social work community.

Heinrich Schiller (Germany), President 1980 – 1988

Thanks to the Editor of this book for the invitation to continue the series of IASSW Presidents with Prof. Dr. Heinrich Schiller, MSW. It is an honour to pay tribute to one of my role models as a social worker and social work teacher and to a friend of many years.

Dr. Ralph Garber (Canada), President 1988 - 1996

A fully revealing portrait of Ralph Garber would require a latter-day Boswell. As ordained, however, an attempt must be made to create a recognizable word picture. And it must give initial attention to the range of influences and factors in Ralph Garber's inheritance and environment that, throughout his life, he experienced, absorbed and utilized in his remarkably creative career.