What's Relatively New? We resurveyed 9 of 11 short arrays across the Kern Front fault on 24 May 2007, concluding that the vertical displacement is continuing at a rate of 5 mm/yr. We resurveyed the Nyland Ranch nail line on 11 May 2002, and then a M4.9 earthquake occurred on the Sargent fault at 2129 hrs on 13 May 2002. As of 11 May,, the creep rate continued to be 12 mm/yr, but more importantly, the residuals flattened indicating no creep retardation, and suggesting, therefore, no significant earthquake imminent in the area for perhaps the next 2-3 years. An earthquake on the Sargent fault may not count, but it will be interesting to see what effect that earthquake had on the array (Modified 15 May 2002). We performed in 2001 the sixth releveling of the bench marks established across the Teton fault in 1988. The results of the survey may be viewed on the Teton page, together with picutres of the crew and their activities. Here is the text of the abstract submitted in September 2001 to the American Geophysical Union for consideration for presentation in the annual Fall meeting in December in San Francisco: First-order Leveling and Campaign GPS Reveal Anomalous, Interseismic, Contractile, Transient Strain Across Teton Normal Fault, 1988-2001, Grand Teton National Park, Wyoming A. G. Sylvester (Univ. California, Santa Barbara CA), R. B. Smith and Wu Lung Chang (Univ. Utah, Salt Lake City, UT), C. S. Hitchcock (Wm. Lettis & Assoc., Inc., Walnut Creek, CA), and J. O. D. Byrd (Paradigm Geophys., Houston, TX) As part of a comprehensive neotectonic study of interseismic behavior of active faults, we have done six first order leveling surveys of 50 permanent bench marks in a 22 km-long base line across the Teton fault to characterize its interseismic behavior between 1988 and 2001. This 55 km-long normal fault extends along the eastern base of the Teton Range, exhibits up to 30 m of post-glacial offset, and has one the highest rates of Holocene slip of any fault in the Basin-Range. It is seismically dormant at the M2+ level, however, and presently lies in the center of a 50 km-long seismic gap. Results of five of the six levelings are remarkably similar and suggest that the alluvium-filled valley of northern Jackson Hole (hanging wall) subsided 6-8 mm relative to bedrock of the Teton Range (footwall) relative to the 1989 survey. In 1997, however, a 2 km-wide zone adjacent to the fault rose 12 mm relative to the 1993 survey, and then dropped 16 mm by the 2001 leveling. This zone coincides with an area of low topography characterized by lakes ponded along the fault and south-flowing streams parallel to the range front, rather than eastward away from the range. This subsidence zone records hanging wall subsidence related to long term faulting. The 1997 uplift of the valley floor and subsidence zone may reflect an unexpected, reverse loading and local crustal shortening between 1993 and 2001. Campaign GPS surveys (1987 to 2000) support this hypothesis, indicating that the principal horizontal strain axis is locally E-W perpendicular to the fault, and suggesting crustal shortening occurred in the period 1995-2000. Regionally during 1987-1995, subsidence and contraction characterized deformation of the Yellowstone caldera only 30 km to the north, when GPS recorded uplift and extension across the Teton fault. During 1995-2000, subsidence slowed or ceased for much of the caldera, whereas the overall GPS vectors across Jackson Hole were directed west with almost 2 mm/yr of E-W motion (N. America fixed). This strain field would load the east-dipping Teton normal fault in contraction, implying that the regional stress field was compressional against the fault at the time of the 2000 GPS survey. The return of the 2001 leveling signal to pre-1997 values suggests that the strain reversed, and that the 1997 leveling anomaly was a contractile strain transient that passed across the fault probably between 1995 when the strain pattern at Yellowstone caldera changed and the 2000 GPS survey, but before the 2001 leveling. Preliminary elastic dislocation models indicate 10-20 mm reverse slip at a depth of 1-2 km. Alternatively the observed leveling changes may reflect a complex combination of other processes including local poroelastic effects, or nearfield drag of the hangingwall as it subsides overall in farfield extension. Funded by NSF, NEHRP, UREP, UW/NPS Research Station, Teton Science School The leveling lines in Death Valley and Fish Lake Valley were resurveyed in March 2000 with the main result that height changes within all but the Artist Drive line are negligible. Return to the Title Page