Comparison of fluid tiltmeter data with long‐period seismograms: Surface waves and Earth's free oscillations

Ferreira, Ana M. G.; d’Oreye, Nicolas; Woodhouse, John; Zürn, W.

doi:10.1029/2006jb004311

Cited by 19 publications

(13 citation statements)

References 47 publications

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“…The earthquakes of the 1960s spurred the development of global networks of digital seismometers (Fels & Berger 1994; Stutzmann et al 2000; Butler et al 2004), so that seismic motions can now be measured with a dynamic range of 10 7 with minimal non‐linear distortion. Since the 1964 Alaskan quake, other geophysical technologies have been invented or have grown more precise, so that the seismic motion of great earthquakes can be studied with data from new perspectives, for example, superconducting gravimeters (van Camp 1999), tiltmeters (Ferreira et al 2006) and GPS receivers (Larson et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Long-period toroidal earth free oscillations from the great Sumatra-Andaman earthquake observed by paired laser extensometers in Gran Sasso, Italy

Park

Amoruso

Crescentini

et al. 2008

Geophysical Journal International

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S U M M A R YStrain data recorded by two crossed laser extensometers operating in the Gran Sasso underground observatory recorded seismic free oscillations excited by the 2004 December 26 Sumatra-Andaman earthquake. The main source of instrumental noise can be mitigated by differencing data from the crossed strainmeter arms, so that the resulting differential strain data set offers an unprecedented resolution of the seismic toroidal free oscillations with periods T > 1000 s. We reconstruct the time evolution of selected free-oscillations for comparison with synthetic seismograms that include normal-mode coupling effects from Coriolis force, attenuation and ellipticity. Envelopes estimated for the Gran Sasso differential data set for free oscillations with period T < 1000 s (frequencies f > 1 mHz) are approximated adequately by a composite Centroid-Moment-Tensor (CMT) source with five subevents and an aggregate M w = 9.3 moment-magnitude. Envelopes for several toroidal free oscillations with T > 1000 s are predicted less well. The amplitude of the rarely observed mode 0 T 2 is overpredicted at Gran Sasso by roughly a factor of two, and other modes are underpredicted. The amplitude discrepancy for 0 T 2 is confirmed at selected exceptionally low-noise seismic stations. Hypothetical explanations include a slow-slip component of the seismic moment release, errors in the composite-CMT source model, unmodelled coupling effects to Earth's secular modes and feedback from the Sumatra-Andaman tsunami on Indian Ocean coastlines. Of these hypotheses, either an extended-duration strain release or tsunami feedback seem most plausible. The viability of the tsunami-feedback mechansim deserves further investigation.

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Section: Introductionmentioning

confidence: 99%

Long-period toroidal earth free oscillations from the great Sumatra-Andaman earthquake observed by paired laser extensometers in Gran Sasso, Italy

Park

Amoruso

Crescentini

et al. 2008

Geophysical Journal International

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“…accelerate a full cup of hot coffee horizontally without tilting it and a painful experience will be the result). Examples for this are presented by Ferreira et al (2006) using records of the free oscillations excited by the great 2004 N. Sumatra–Andaman Islands quake from a 40 m water‐tube tiltmeter in Luxembourg and from a 120 m differential‐pressure fluid‐tiltmeter at Black Forest Observatory (BFO, see below). Comparing the data with predictions demonstrates that these tiltmeters sense predominantly the inertial accelerations associated with the toroidal modes, which on a spherically symmetric earth do not cause tilts.…”

Section: Introductionmentioning

confidence: 99%

On reduction of long-period horizontal seismic noise using local barometric pressure

Zürn¹,

Exß²,

Steffen

et al. 2007

Geophysical Journal International

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S U M M A R YTilt from atmospheric loading has long been known to be the major source of long-period horizontal seismic noise. We try to quantify these effects for seismic data from the Black Forest Observatory (BFO), which is known to be a very quiet station. Experimental transfer functions between local barometric pressure and horizontal seismic noise are estimated for two long time-series by standard methods. Two simple analytical physical models are developed: the local deformation model (LDM) and the acoustic-gravity wave model (TWM). Subsequently these models, with only two free parameters are fit using least squares to the observed seismic noise for time-series of widely differing lengths. The results are variable, sometimes rather dramatic variance reductions are obtained and sometimes the reduction is hardly significant. The method produces the best results when barometrically induced noise is high. The resulting admittances for the LDM are compared to finite element calculations. Since the methods are simple and can result in conspicuous reductions in noise we provide one more reason for installing barometers at even the best broad-band seismic stations.

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“…Station S1, which is nearest to the slide, exhibits maximum tilt values of approximately −2000 nrad for the x component and 3000 nrad in y direction. Regarding a present‐day tiltmeter accuracy of 1 nrad or less [ d'Oreye and Zürn , 2005; Ferreira et al , 2006; Gebauer et al , 2007], a huge landslide of the Storegga scale will be clearly detectable.…”

Section: Landslide Remote Sensing Via Tiltmetersmentioning

confidence: 99%

Are tilt measurements useful in detecting tsunamigenic submarine landslides?

Brune

Babeyko

Sobolev

2009

Geochem Geophys Geosyst

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[1] Large submarine landslides can generate dangerous tsunamis. Because of their long-period signal, detection of landslides by common seismological methods is difficult. Here we suggest a method of detecting submarine landslides by using an array of land-based tiltmeters. The displacement of a large volume of sediments during landsliding produces a detectable elastic response of the lithosphere. We propose a technique to calculate this response and to invert for tsunami relevant parameters like slide location, volume, and velocity. We exemplify our method by applying it to the Storegga slide west of Norway and other tsunamigenic landslide events. The parameter which can be most robustly estimated from tiltmeter array measurements is the product of slide volume and its velocity (slide tsunamigenic potential). This parameter also controls the amplitude of the generated tsunami wave. The inversion accuracy of this parameter and the estimated tsunami height near the coast depends on the noise level of tiltmeter measurements, distance of the tiltmeters from the slide, and slide tsunamigenic potential itself. The tsunamigenic potential of the most dangerous slides like Storegga can be estimated well by tiltmeters at the coast if the effective noise level does not exceed 50 nrad.

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Comparison of fluid tiltmeter data with long‐period seismograms: Surface waves and Earth's free oscillations

Cited by 19 publications

References 47 publications

Long-period toroidal earth free oscillations from the great Sumatra-Andaman earthquake observed by paired laser extensometers in Gran Sasso, Italy

Long-period toroidal earth free oscillations from the great Sumatra-Andaman earthquake observed by paired laser extensometers in Gran Sasso, Italy

On reduction of long-period horizontal seismic noise using local barometric pressure

Are tilt measurements useful in detecting tsunamigenic submarine landslides?

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