Modern observations of the effect of earthquakes on the Chandler wobble

Smylie, D. E.; Henderson, Gary; Zuberi, Midhat

doi:10.1016/j.jog.2014.09.012

Cited by 8 publications

(9 citation statements)

References 18 publications

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“…In fact, we must verify whether or not earthquakes can induce polar motion comparable with that due to these surface ice loadings. From the analysis of Earth Orientation Parameters (EOP) time-series from modern space measurement techniques (Lunar and Satellite Laser Ranging and Very Long Baseline Interferometry), it will be also possible to discriminate between the different sources of polar motion excitation by determining breaks in the prograde circular motion of the rotation pole corresponding to sudden excitations associated with large seismic events (Smylie & Zuberi 2009;Smylie et al 2015).…”

mentioning

confidence: 99%

Residual polar motion caused by coseismic and interseismic deformations from 1900 to present

Cambiotti¹,

Wang

Sabadini³

et al. 2016

Geophys. J. Int.

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We challenge the perspective that seismicity could contribute to polar motion by arguing quantitatively that, in first approximation and on the average, interseismic deformations can compensate for it. This point is important because what we must simulate and observe in Earth Orientation Parameter time-series over intermediate timescales of decades or centuries is the residual polar motion resulting from the two opposing processes of coseismic and interseismic deformations. In this framework, we first simulate the polar motion caused by only coseismic deformations during the longest period available of instrumental seismicity, from 1900 to present, using both the CMT and ISC-GEM catalogues. The instrumental seismicity covering a little longer than one century does not represent yet the average seismicity that we should expect on the long term. Indeed, although the simulation shows a tendency to move the Earth rotation pole towards 133 • E at the average rate of 16.5 mm yr −1 , this trend is still sensitive to individual megathrust earthquakes, particularly to the 1960 Chile and 1964 Alaska earthquakes. In order to further investigate this issue, we develop a global seismicity model (GSM) that is independent from any earthquake catalogue and that describes the average seismicity along plate boundaries on the long term by combining information about presentday plate kinematics with the Anderson theory of faulting, the seismic moment conservation principle and a few other assumptions. Within this framework, we obtain a secular polar motion of 8 mm yr −1 towards 112.5 • E that is comparable with that estimated from 1900 to present using the earthquake catalogues, although smaller by a factor of 2 in amplitude and different by 20 • in direction. Afterwards, in order to reconcile the idea of a secular polar motion caused by earthquakes with our simplest understanding of the seismic cycle, we adapt the GSM in order to account for interseismic deformations and we use it to quantify, for the first time ever, their contribution to polar motion. Taken together, coseismic and interseismic deformations make the rotation pole wander around the north pole with maximum polar excursions of about 1 m. In particular, the rotation pole moves towards about Newfoundland when the interseismic contribution dominates over the coseismic ones (i.e. during phases of low seismicity or, equivalently, when most of the fault system associated with plate boundaries is locked). When megathrust earthquakes occur, instead, the rotation pole is suddenly shifted in an almost opposite direction, towards about 133 • E.

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mentioning

confidence: 99%

Residual polar motion caused by coseismic and interseismic deformations from 1900 to present

Cambiotti¹,

Wang

Sabadini³

et al. 2016

Geophys. J. Int.

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show abstract

“…In this model the pole would proceed at a uniform rate along a circular arc centered at the secular pole until the exact time of the earthquake. At the time of the earthquake, the secular pole would shift and the pole would proceed at a uniform rate along a new circular arc centered at the new secular pole [11]. There appear to be some premonitory signs of large earthquakes in the pole path.…”

Section: Introductionmentioning

confidence: 99%

Variations of seismic activity caused by the Chandler Wobble

2019

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The problem of the correlation of the global dynamic phenomenon “Chandler wobble” with the local dynamics in different parts of the Earth’s crust and lithosphere is wide of the solution. In this study, an attempt was made to approach the solution by analyzing the temporal variations of local seismic activity in the restricted geospace volumes (GSV) within the uniform seismoactive regions. The driver of Chandler wobble is the deep mantle – the most hard and most massive Earth’s layer, whose large inertia tensor value is able to keep up Chandler’s specific rotation of the Earth for a long time. We use the geocentric coordinate system where daily rotation is absent. In this system Chandler wobble is very slow rotation of the Earth around the current equatorial axis (the pole of which is denoted as EP14). Probably, this slow rotation can influence on the seismic events in the GSV. This influence is proposed to determine by the some statistical parameter EP14gsv that indicates the most typical position EP14 on equator when the most part of the earthquakes have occurred in the given GSV. For some geospace volumes the distribution indicates certain longitudes, where the number of seismic events is maximal or minimal.

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“…But the time-varying periodic obtained by these methods will be corrupted easily by noise components, especially in the case when a large amounts of noise exist in the mixed signals because these methods choose a frequency band range in which may exist a lot of noises. In addition, other spatio-temporal analysis methods are also used to extracting the time-varying periodic signals, such as the singular spectrum analysis (SSA) (Chen et al 2013), and empirical mode decomposition (EMD) (Smylie et al 2015). However, when implementing the SSA, a key problem is choosing an appropriate lag-window size that determines the spectral resolution of the algorithm (Chen et al 2013); EMD has the problem of mode mixing (Wu and Huang 2009).…”

Section: Introductionmentioning

confidence: 99%

On the capabilities of the inaction method for extracting the periodic components from GPS clock data

Wang

Liu

et al. 2018

GPS Solut

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Almost all GPS signal clocks show a periodic fluctuation. Harmonics in GPS satellites are a well-known feature, such as 3-, 4-, 6-and 12-h terms, accurate extraction of these harmonics are helpful to improve the clock modeling. The inaction method (IM) originating from the concept of normal time-frequency transform (NTFT) can precisely extract the periodic signals which significantly present the NTFT spectrum. This method is essentially line-pass filtering, so it can avoid being polluted by noises to the maximum extent and then have the ability to extract the time-varying periodic signals with robustness. The simulation test demonstrates that IM is the best method for extracting the harmonics and time-varying harmonics from a time signal, compared to singular spectrum analysis and zero-phase digital filter. We focus on GPS satellite clock data, after removing 6-and 12-h terms extracted by IM, the oscillation phenomenon in Hadamard deviation virtually disappears; this demonstrates that these periodic signals have been extracted effectively by the IM.

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Modern observations of the effect of earthquakes on the Chandler wobble

Cited by 8 publications

References 18 publications

Residual polar motion caused by coseismic and interseismic deformations from 1900 to present

Residual polar motion caused by coseismic and interseismic deformations from 1900 to present

Variations of seismic activity caused by the Chandler Wobble

On the capabilities of the inaction method for extracting the periodic components from GPS clock data

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