Strain accumulation in the Rocky Mountain states

Savage, J. C.; Lisowski, M.; Prescott, W. H.

doi:10.1029/jb090ib12p10310

Cited by 20 publications

(15 citation statements)

References 18 publications

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“…On the basis of relocated teleseismically recorded aftershocks for the Hebgen Lake earthquake,Dewey et al [1972, p. 886] suggest that "the fault surface of the main shock at depth extended a considerable distance east and west of the surface fault scarps. "Savage et al [1985] reached this same conclusion from analysis of horizontal strain measurements.…”

supporting

confidence: 56%

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Evidence for postseismic viscoelastic relaxation following the 1959 M = 7.5 Hebgen Lake, Montana, Earthquake

Reilinger¹

1986

J. Geophys. Res.

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A 1983 releveling survey conducted by the National Geodetic Survey, combined with previous surveys in 1923, 1960, 1967, and 1975, provides evidence for ongoing vertical deformation of a broad region (diameter of ∼150 km) surrounding the site of the 1959 Hebgen Lake earthquake. Deformation consists of relative uplift centered roughly on the coseismic fault and a smaller amplitude zone of relative subsidence south of the fault. Maximum observed elevation change during the postseismic period (1960–1983) exceeds 30 cm. Assuming that the entire uplift (i.e., 1923–1983) occurred following the 1959 earthquake (i.e., uplift measured between 1923 and 1960 was entirely postseismic), the rate of vertical deformation appears to have decreased exponentially with a characteristic decay time of about 10 years. The spatial pattern and time behavior of the observed movements are consistent with simple models of postseismic deformation following normal faulting in an elastic layer (thickness of ∼30–40 km) overlying a viscoelastic half‐space (viscosity of ∼1019 Pa s). This model may also account for the anomalously large horizontal strain around the Hebgen Lake region measured by repeated trilateration surveys during the period 1973–1984. The releveling measurements in the Hebgen Lake region appear to provide the first observations of viscoelastic relaxation in the asthenosphere following an intraplate earthquake in the United States.

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supporting

confidence: 56%

“…Additional evidence for postearthquake deformation in the Hcbgen Lake area was reported by Prescott et al [1979] and Savage et al [1985] on the basis of trilateration surveys conducted by the U.S. Geological Survey (USGS) since 1973. These measurements indicate uniaxial extension perpendicular to the 1959 rupture trace at a rate of 0.28 + 0.02 #strain/yr.…”

mentioning

confidence: 79%

Evidence for postseismic viscoelastic relaxation following the 1959 M = 7.5 Hebgen Lake, Montana, Earthquake

Reilinger¹

1986

J. Geophys. Res.

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“…2) has, however, been attributed to water pumping near Albuquerque (Reilinger et al 1980). While horizontal strain rates of this magnitude were recorded in the vicinity of Socorro during a 1972-1984 trilateration survey (Savage et al 1985), the inferred strains revealed no systematic temporal pattern, and in fact changed their sign during the period of observation. the preferred model of Larsen et al 1986) would imply a surface contraction in these areas giving rise to a strain rate of the order of (subsidence rate)/ (source depth).…”

Section: Origin Of Uplift: Continual Magma Injection or In Situ Melting?mentioning

confidence: 92%

“…Note that the spherical deflation sources in the middle crust beneath Belen and Socorro (i.e. The absence of a systematic strain accumulation in the trilateration data of Savage et al (1985) argues against volume changes in the middle crust below the Rio Grande rift. That is, for a subsidence rate of several millimetres per year and a source depth of 19 km, the corresponding strain rate is O(10 x7 yr x1 ).…”

Section: Origin Of Uplift: Continual Magma Injection or In Situ Melting?mentioning

confidence: 99%

Finite source modelling of magmatic unrest in Socorro, New Mexico, and Long Valley, California

Fialko¹,

Simons²,

Khazan³

2001

Geophysical Journal International

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SUMMARY We investigate surface deformation associated with currently active crustal magma bodies in Socorro, New Mexico, and Long Valley, California, USA. We invert available geodetic data from these locations to constrain the overall geometry and dynamics of the inferred deformation sources at depth. Our best‐fitting model for the Socorro magma body is a sill with a depth of 19 km, an effective diameter of 70 km and a rate of increase in the excess magma pressure of 0.6 kPa yr−1. We show that the corresponding volumetric inflation rate is ∼6×10−3 km3 yr−1, which is considerably less than previously suggested. The measured inflation rate of the Socorro magma body may result from a steady influx of magma from a deep source, or a volume increase associated with melting of the magma chamber roof (i.e. crustal anatexis). In the latter case, the most recent major injection of mantle‐derived melts into the middle crust beneath Socorro may have occurred within the last several tens to several hundreds of years. The Synthetic Interferometric Aperture Radar (InSAR) data collected in the area of the Long Valley caldera, CA, between June 1996 and July 1998 reveal an intracaldera uplift with a maximum amplitude of ∼11 cm and a volume of 3.5×10−2 km3. Modelling of the InSAR data suggests that the observed deformation might be due to either a sill‐like magma body at a depth of ∼12 km or a pluton‐like magma body at a depth of ∼8 km beneath the resurgent dome. Assuming that the caldera fill deforms as an isotropic linear elastic solid, a joint inversion of the InSAR data and two‐colour laser geodimeter data (which provide independent constraints on horizontal displacements at the surface) suggests that the inferred magma chamber is a steeply dipping prolate spheroid with a depth of 7–9 km and an aspect ratio in excess of 2:1. Our results highlight the need for large radar look angles and multiple look directions in future InSAR missions.

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“…Grande (Savage et al 1985), Baikal (Calais et al 1998), and the Rhine Graben (Ahorner 1983). Elsewhere, opening rates are based on magnetic lineations in the Woodlark Rift (Taylor et al 1995) and the Red Sea-Gulf of Suez.…”

Section: Seismicity In Riftsmentioning

confidence: 99%

Evidence for seismogenic normal faults at shallow dips in continental rifts

Abers

2001

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Several recent observations indicate that normal faulting earthquakes occasionally occur on faults dipping <35 ° , dips often considered shallow. Most of these occur in the Woodlark and Aegean rifts. These two rifts are found to generate significantly more earthquakes than others and are the most rapidly extending, and so display the widest variety of fault behaviour. Even within the Woodlark Rift system extension rates vary along strike, with the shallowest-dipping faults confined to the most rapidly rifting segment. Here, several events (Mw 6.0-6.8) feature nodal planes dipping 23-35 °. These planes are subparallel to shear zones bounding nearby metamorphic core complexes, including one imaged to 8-9km depth by seismic reflection profiling.

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Strain accumulation in the Rocky Mountain states

Cited by 20 publications

References 18 publications

Evidence for postseismic viscoelastic relaxation following the 1959 M = 7.5 Hebgen Lake, Montana, Earthquake

Evidence for postseismic viscoelastic relaxation following the 1959 M = 7.5 Hebgen Lake, Montana, Earthquake

Finite source modelling of magmatic unrest in Socorro, New Mexico, and Long Valley, California

Evidence for seismogenic normal faults at shallow dips in continental rifts

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