A Network of Superconducting Gravimeters Detects Submicrogal Coseismic Gravity Changes

Imanishi, Yuichi; Sasajima, Tadahiro; Higashi, Tomohito; Sun, Wenke; Okubo, Shuhei

doi:10.1126/science.1101875

Cited by 121 publications

(89 citation statements)

References 12 publications

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“…This mass redistribution induces changes in the Earth's gravitational field. Permanent gravity changes generated by static deformation induced by the co-seismic and post-seismic slip of large earthquakes have been observed by superconducting gravimeters and gravity field satellite missions on multiple occasions (Imanishi et al 2004;Wang et al 2012a;Fuchs et al 2013;Cambiotti & Sabadini 2013). Theoretical models of these static gravity perturbations have been developed (Okubo 1992;Sun et al 2009) and compared to observations (Matsuo & Heki 2011;Wang et al 2012b).…”

Section: Introductionmentioning

confidence: 99%

Transient gravity perturbations induced by earthquake rupture

Harms

Ampuero

Barsuglia

et al. 2015

Geophysical Journal International

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S U M M A R YThe static and transient deformations produced by earthquakes cause density perturbations which, in turn, generate immediate, long-range perturbations of the Earth's gravity field. Here, an analytical solution is derived for gravity perturbations produced by a point double-couple source in homogeneous, infinite, non-self-gravitating elastic media. The solution features transient gravity perturbations that occur at any distance from the source between the rupture onset time and the arrival time of seismic P waves, which are of potential interest for real-time earthquake source studies and early warning. An analytical solution for such prompt gravity perturbations is presented in compact form. We show that it approximates adequately the prompt gravity perturbations generated by strike-slip and dip-slip finite fault ruptures in a half-space obtained by numerical simulations based on the spectral element method. Based on the analytical solution, we estimate that the observability of prompt gravity perturbations within 10 s after rupture onset by current instruments is severely challenged by the background microseism noise but may be achieved by high-precision gravity strainmeters currently under development. Our analytical results facilitate parametric studies of the expected prompt gravity signals that could be recorded by gravity strainmeters.

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Section: Introductionmentioning

confidence: 99%

Transient gravity perturbations induced by earthquake rupture

Harms

Ampuero

Barsuglia

et al. 2015

Geophysical Journal International

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“…Observing changes in gravity is one of the most powerful methods for detecting mass redistributions associated with solid-earth tectonics, such as those resulting from earthquakes and volcanism (Furuya et al, 2003;Imanishi et al, 2004). However, gravity measurements are also sensitive to changes in land-water distributions in the vicinity of gravimeters.…”

Section: Introductionmentioning

confidence: 99%

Gravity changes associated with variations in local land-water distributions: Observations and hydrological modeling at Isawa Fan, northern Japan

et al. 2012

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Gravity changes associated with variations in local land-water distributions have been observed at Isawa Fan in northern Japan, and modeled by hydrological equations. We solve the Richards equation numerically for the time variation in the vertical soil moisture distribution, which is then spatially integrated to estimate gravity changes due to the soil moisture distribution. In modeling Isawa Fan, we assume a simple hydrological model: a horizontally homogeneous soil in an infinite half-space. The estimated gravity is consistent with the observed gravity during a 50-day period within about 0.4 µgal root mean square, owing to both observed soil parameter values and the observation building geometry being incorporated into the hydrological model. However, the estimated gravity cannot fully reproduce annual gravity changes observed during a 2-year time frame, because the boundary conditions in the modeling determine only local water distributions and the resultant short-period gravity changes. Instead, the observed gravity over these 2 years can be reproduced within about 1.0 µgal root mean square, if the additional parameters of the annual gravity change (A ac and A as ) and the snowfall effect (A s ) are calculated by the function regression to the observed gravity with the least-squares method. The hydrological modeling techniques presented here can be utilized at all gravity sites in flat areas similar to Isawa Fan, such that hydrological effects in gravity data can be corrected and mass transfers associated with earthquakes and volcanoes can be monitored.

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“…It is now the best instrument to survey the temporal gravity variations in the world. It has the potential to detect almost all signatures with periods ranging from serveral seconds related to coseimic movements to several years related to the variations in the Earth's rotation, even the phenomena associated with the secular tectonic movements of local crust, such as the the Earth's free oscillations (Banka and Crossley 1999;Van Camp 1999;Lei et al 2005;Park et al 2005), the Earth's tides (Sun et al 2001;Xu et al 2004a), the load effects of barometric pressure (Sun and Lou 1998), the nearly diurnal resonance (Defraigne et al 1994;Xu et al 2002), translational oscilations of the solid inner core (Smylie 1992;Courtier et al 2000;Rosat et al 2003;Xu et al 2010), Polar motion (Loyer et al 1999;Xu et al 2004b), secular crust deformation due to earthquakes or other reasons Imanishi et al 2004;Richter et al 2004;Xu et al 2008) and so on. As a result, a significant scientific project, i.e., the Global Geodynamics Project, has been carried out since 1997 in order to investigate global and local dynamic problems using continuous gravity data from a worldwide network of superconducting gravimeters Crossley 2004;Crossley and Hinderer 2009).…”

Section: Introductionmentioning

confidence: 99%

Results of Gravity Observations Using a Superconducting Gravimeter at the Tibetan Plateau

Sun¹,

Xu²,

Chen³

et al. 2013

Terr. Atmos. Ocean. Sci.

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The tidal and nontidal gravity change characteristics in the Tibetan Plateau region were investigated using the continuous gravity measurements recorded with a superconducting gravimeter (SG) installed in Lhasa from December 8, 2009 to September 30, 2011. The results indicated that the precision of the tidal gravity observations with the SG in Lhasa was very high. The standard deviation of the harmonic analysis for the gravity tides was 0.498 nm s -2 , and the uncertainties of amplitude factors in the four main tidal waves (i.e., O 1 , K 1 , M 2 and S 2 ) were better than 0.002%. In addition, the diurnal gravity tide observations clearly revealed a pattern of nearly diurnal resonance. As a result, it is affirmed that the station should act as a local tidal gravity reference in the Tibetan Plateau and its adjacent regions. The load effects of oceanic tides are so weak that the resulting perturbation in the gravimetric factors is less than 0.6%. However, the load effects of the local atmosphere on either the tidal or the nontidal gravity observations are significant, although no seasonal variations have been found. After removing the atmospheric effects, the standard deviation of the harmonic analysis for the gravity tides decreased obviously from 4.160 to 0.498 nm s -2 . Having removed the load effects of oceanic tides and local atmosphere, it is found that the tidal gravity observations are significantly different from those expected theoretically, which may be related to active tectonic movement and extremely thick crust in the Tibetan Plateau region. In addition, the Earth's free oscillations excited by 2011 Tohoku-Oki M w 9.0 Earthquake were successfully detected.

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A Network of Superconducting Gravimeters Detects Submicrogal Coseismic Gravity Changes

Cited by 121 publications

References 12 publications

Transient gravity perturbations induced by earthquake rupture

Transient gravity perturbations induced by earthquake rupture

Gravity changes associated with variations in local land-water distributions: Observations and hydrological modeling at Isawa Fan, northern Japan

Results of Gravity Observations Using a Superconducting Gravimeter at the Tibetan Plateau

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