Vertical surface displacements at Yellowstone Caldera, Wyoming, 1976–1986

Abstract

Between first‐order leveling surveys in 1976 and 1986, the east central floor of Yellowstone caldera rose 15.4 ± 1.4 mm/yr and the west central floor rose 17.0 ± 2.0 mm/yr with respect to points on the south caldera rim. The same pattern has prevailed since an initial survey in 1923, except that the western caldera rose 30% faster during 1976–1986 than during 1923–1976. The 1976–1986 uplift extends beyond the northwest caldera rim near the adjacent Hebgen Lake fault zone, site of a magnitude 7.3 earthquake in August 1959. Marginally significant displacements in the eastern caldera suggest that uplift continued during 1983–1984, stopped during 1984–1985, and reversed to subsidence during 1985–1986; thus long‐term uplift may accumulate episodically. Historical uplift is especially noteworthy because regional crustal extension and thermal contraction during cooling would cause the caldera floor to subside if other processes were not acting to warp it upward. The pattern and dimensions of the uplift indicate a source in the upper crust beneath Yellowstone caldera, probably a reservoir of rhyolite magma within a cooling granitic pluton. A simple point source model would suggest a source 10–15 km deep, but the reservoir is probably lens‐shaped and closer to the surface. Uplift may be caused by basaltic intrusions near the base of the reservoir or accumulation of magmatic fluids during cooling and crystallization within the reservoir. Subsidence might be a response to regional tectonic extension or release of trapped magmatic fluids. Magmatic inflation, volatile accumulation, and crustal extension may culminate eventually in renewed eruptive activity, but there is no evidence of an imminent volcanic hazard.

Seismic moment tensor resolution by waveform inversion of a few local noisy records-II. Application to the Phlegraean Fields (Southern Italy) volcanic tremors

“…Since January 1985, the area has been slowly sinking (30 cm by the end of 1986), but the seismicity has stayed at very low levels. Similar behaviour, although less well documented, has been observed during the 1970-1972 bradyseismic activity ( Barberi et al 1989) and occasionally in other calderas, such as Yellowstone, USA (Dzurisin & Yamashita 1987), Long Valley, USA (Savage et al 1987) and Rabaul, New Guinea (McKee, .…”

Spatio-temporal evolution of Yellowstone deformation between 1992 and 2009 from InSAR and GPS observations

“…Approximately 50 rhyolitic and basaltic events occurred since this last cataclysmic eruption in association with the development of Yellowstone caldera, with the youngest events occurring at around 70 ka . Although no eruptions occurred since 70 ka, the Yellowstone volcanic system is still active as indicated by its alternating decadal episodes of subsidence and uplift, widespread hydrothermal activity, and extensive seismicity (e.g., Pelton and Smith 1979;Dzurisin and Yamashita 1987;Dzurisin et al 1990Dzurisin et al , 1994Waite and Smith 2002;Wicks et al 1998Wicks et al , 2006.…”

“…1) is one of the most concentrated regions of magmatic, hydrothermal, and seismic activity in North America (e.g., Pelton and Smith 1979;Dzurisin and Yamashita 1987;Dzurisin et al 1990Dzurisin et al , 1994Christiansen 2001;Waite and Smith 2002;Vasco et al 2007;Aly et al 2009). It is thus a critical region in which regular monitoring is required to track the evolution of potentially hazardous events that may affect millions of people.…”

Renewed uplift at the Yellowstone Caldera measured by leveling surveys and satellite radar interferometry

“…1; Smith 1979, 1982). Less extensive, annual surveys starting in 1983 showed additional uplift from 1976 to 1984 (22B1 mm/year) followed by progressive subsidence from 1985 to 1995 at an average rate of -19B1 mm/year (Dzurisin and Yamashita 1987;Dzurisin et al 1990Dzurisin et al , 1994. This paper compares leveling and satellite radar interferometry results for the period 1992-1998, including the most recent leveling survey in September 1998.…”

“…Specific procedures and accuracy for the 1975-1995 surveys at Yellowstone were discussed previously Smith 1979, 1982;Dzurisin and Yamashita 1987;Dzurisin et al 1990Dzurisin et al , 1994. For the most part, the same discussion applies to the 1998 survey.…”