Global Imaging of the Earth's Deep Interior: Seismic Constraints on (An)isotropy, Density and Attenuation

Trampert, Jeannot; Fichtner, Andreas

doi:10.1002/9781118529492.ch11

Cited by 10 publications

(8 citation statements)

References 151 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The lack of information with its resulting nonuniqueness is compensated by regularization, e.g., in the form of smoothing and damping. Since regularization is to some degree subjective, resolution estimates tend to be biased [Trampert and Fichtner, 2013]. Furthermore, the existence of multiple plausible solutions that explain the data equally well is not taken into account.…”

Section: Probabilistic Finite Source Inversionmentioning

confidence: 99%

Reducing nonuniqueness in finite source inversion using rotational ground motions

2014

View full text Add to dashboard Cite

We assess the potential of rotational ground motion recordings to reduce nonuniqueness in kinematic source inversions, with emphasis on the required measurement accuracy of currently developed rotation sensors. Our analysis is based on synthetic Bayesian finite source inversions that avoid linearizations and provide a comprehensive quantification of uncertainties and trade-offs. Using the fault and receiver geometry of the Tottori 2000 earthquake as a test bed, we perform inversions for two scenarios: In scenario I, we use translational velocity recordings only. In scenario II, we randomly replace half of the velocity recordings by rotation recordings, thus keeping the total amount of data constant. To quantify the noise-dependent impact of rotation recordings, we perform a sequence of inversions with varying noise levels of rotations relative to translations. Our results indicate that the incorporation of rotational ground motion recordings can significantly reduce nonuniqueness in finite source inversions, provided that measurement uncertainties are similar to or below the uncertainties of translational velocity recordings. When this condition is met, rupture velocity and rise time benefit most from rotation data. The trade-offs between both parameters are then strongly reduced, and the information gain nearly doubles. This suggests that rotational ground motion recordings may improve secondary inferences that rely on accurate information about rise time and rupture velocity. These include frictional properties of the fault, radiation directivity, and ground motion in general.

show abstract

Section: Probabilistic Finite Source Inversionmentioning

confidence: 99%

Reducing nonuniqueness in finite source inversion using rotational ground motions

2014

View full text Add to dashboard Cite

show abstract

“…It follows that the apparent variations in attenuation induced by 3-D density structure can be on the order of tens of percent, thus being comparable to attenuation heterogeneities found on regional and global scales (e.g. Mitchell, 1995;Romanowicz, 1995;Haberland and Rietbrock, 2001;Selby and Woodhouse, 2002;Dalton et al, 2008;Kennett and Abdullah, 2011;Trampert and Fichtner, 2013;Zhu et al, 2015). This result highlights that 3-D density structure should be taken into account when using fullwaveform techniques to invert for 3-D variations in attenuation.…”

Section: Attenuation Bias Estimationmentioning

confidence: 70%

“…The physical origin of this nearly complete absence of sensitivity lies in the scattering characteristics of density heterogeneities. When a body wave reaches a density perturbation, the resulting scattered wave propagates backwards, meaning that it cannot interfere with the incident wave unless the heterogeneity is located within one wavelength from either source or receiver (Wu and Aki, 1985;Tarantola, 1986;Trampert and Fichtner, 2013). This is in contrast to the scattered wave caused by a velocity heterogeneity, which propagates along with the incident wave, thereby leading to a finite-frequency travel-time shift (e.g.…”

Section: Introductionmentioning

confidence: 82%

The imprint of crustal density heterogeneities on regional seismic wave propagation

2016

Self Cite

View full text Add to dashboard Cite

Abstract. Density heterogeneities are the source of mass transport in the Earth. However, the 3-D density structure remains poorly constrained because travel times of seismic waves are only weakly sensitive to density. Inspired by recent developments in seismic waveform tomography, we investigate whether the visibility of 3-D density heterogeneities may be improved by inverting not only travel times of specific seismic phases but complete seismograms.As a first step in this direction, we perform numerical experiments to estimate the effect of 3-D crustal density heterogeneities on regional seismic wave propagation. While a finite number of numerical experiments may not capture the full range of possible scenarios, our results still indicate that realistic crustal density variations may lead to travel-time shifts of up to ∼ 1 s and amplitude variations of several tens of percent over propagation distances of ∼ 1000 km. Both amplitude and travel-time variations increase with increasing epicentral distance and increasing medium complexity, i.e. decreasing correlation length of the heterogeneities. They are practically negligible when the correlation length of the heterogeneities is much larger than the wavelength. However, when the correlation length approaches the wavelength, density-induced waveform perturbations become prominent. Recent regional-scale full-waveform inversions that resolve structure at the scale of a wavelength already reach this regime.Our numerical experiments suggest that waveform perturbations induced by realistic crustal density variations can be observed in high-quality regional seismic data. While density-induced travel-time differences will often be small, amplitude variations exceeding ±10 % are comparable to those induced by 3-D velocity structure and attenuation.While these results certainly encourage more research on the development of 3-D density tomography, they also suggest that current full-waveform inversions that use amplitude information may be biased due to the neglect of 3-D variations in density.

show abstract

“…Differences between 1-D Q models typically range between 10 and 100 per cent (e.g. Dziewoński & Anderson 1981;Widmer et al 1991;Durek & Ekström 1996;Resovsky et al 2005;Trampert & Fichtner 2013).…”

Section: Discussion a N D C O N C L U S I O N Smentioning

confidence: 99%

Models and Fréchet kernels for frequency-(in)dependent Q

Fichtner¹,

Driel²

2014

Geophysical Journal International

Self Cite

View full text Add to dashboard Cite

We present a new method for the modelling of frequency-dependent and frequencyindependent Q in time-domain seismic wave propagation. Unlike previous approaches, attenuation models are constructed such that Q as a function of position in the Earth appears explicitly as a parameter in the equations of motion. This feature facilitates the derivation of Fréchet kernels for Q using adjoint techniques. Being simple products of the forward strain field and the adjoint memory variables, these kernels can be computed with no additional cost, compared to Fréchet kernels for elastic properties. The same holds for Fréchet kernels for the power-law exponent of frequency-dependent Q, that we derive as well. To illustrate our developments, we present examples from regional-and global-scale time-domain wave propagation.

show abstract

Global Imaging of the Earth's Deep Interior: Seismic Constraints on (An)isotropy, Density and Attenuation

Cited by 10 publications

References 151 publications

Reducing nonuniqueness in finite source inversion using rotational ground motions

Reducing nonuniqueness in finite source inversion using rotational ground motions

The imprint of crustal density heterogeneities on regional seismic wave propagation

Models and Fréchet kernels for frequency-(in)dependent Q

Contact Info

Product

Resources

About