Shear wave anisotropy beneath the Aegean inferred from SKS splitting observations

Evangelidis, Christos; Liang, Wen‐Tzong; Melis, Νikolaos S.; Konstantinou, K. I.

doi:10.1029/2010jb007884

Cited by 41 publications

(52 citation statements)

References 53 publications

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“…Only seismic anisotropy (Fig. 10a, Paul et al, 2010;Hatzfeld et al, 2001;Evangelidis et al, 2011) possibly advocates for alongarc mantle flow that could be interpreted as originating from the Kefalonia window, but the not-so-clear nature of alongarc anisotropy (e.g. Russo and Silver, 1994;Long and Silver, 2009;Faccenna and Capitanio, 2013) prevents from being conclusive.…”

Section: Mantle Flowmentioning

confidence: 99%

“…Subduction rates at the North and South Hellenic trenches occur at rates of 5 to 12 mm yr −1 and 25 to 40 mm yr −1 (e.g. McClusky et al, 1s (Paul et al, 2010) 1s (Evangelidis et al, 2011) 1s (Hatzfeld et al, 2001) − o n ti n e n ta l p la te o c e a n ic p la te 2000; Royden and Papanikolaou, 2011;Pérouse et al, 2012), respectively, which offsets the South and North Hellenic subduction zones by a few tenths of kilometres at present day. The formation of the fault itself results from the entry in the subduction zone of a very negatively buoyant oceanic plate to the south, while in the north the subduction of a continental unit of increasingly positive buoyancy proceeds, as the buoyancy difference of the two plate units suffices to trigger a laterally variable regime along the trench .…”

Section: Geological Settingmentioning

confidence: 99%

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The dynamics of laterally variable subductions: laboratory models applied to the Hellenides

et al. 2013

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Abstract. We designed three-dimensional dynamically selfconsistent laboratory models of subduction to analyse the relationships between overriding plate deformation and subduction dynamics in the upper mantle. We investigated the effects of the subduction of a lithosphere of laterally variable buoyancy on the temporal evolution of trench kinematics and shape, horizontal flow at the top of the asthenosphere, dynamic topography and deformation of the overriding plate. Two subducting units, which correspond to a negatively buoyant oceanic plate and positively buoyant continental one, are juxtaposed via a trench-perpendicular interface (analogue to a tear fault) that is either fully-coupled or shear-stress free. Differential rates of trench retreat, in excess of 6 cm yr −1 between the two units, trigger a more vigorous mantle flow above the oceanic slab unit than above the continental slab unit. The resulting asymmetrical sublithospheric flow shears the overriding plate in front of the tear fault, and deformation gradually switches from extension to transtension through time. The consistency between our models results and geological observations suggests that the Late Cenozoic deformation of the Aegean domain, including the formation of the North Aegean Trough and Central Hellenic Shear zone, results from the spatial variations in the buoyancy of the subducting lithosphere. In particular, the lateral changes of the subduction regime caused by the Early Pliocene subduction of the old oceanic Ionian plate redesigned mantle flow and excited an increasingly vigorous dextral shear underneath the overriding plate. The models suggest that it is the inception of the Kefalonia Fault that caused the transition between an extension dominated tectonic regime to transtension, in the North Aegean, Mainland Greece and Peloponnese. The subduction of the tear fault may also have helped the propagation of the North Anatolian Fault into the Aegean domain.

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Section: Mantle Flowmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

The dynamics of laterally variable subductions: laboratory models applied to the Hellenides

et al. 2013

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“…The recorded delay time between these two components is a function of the severity of the anisotopy and the thickness of the anisotropic layer. The shear wave anisotropy studies that I use here are representative down to a depth of around 200 km or more in eastern Turkey (34) and the eastern part of NAFZ (35) being possibly shallower farther west (36). P n waves, on the other hand, propagate typically below the Moho discontinuity along approximately horizontal rays apart from source and receiver legs.…”

mentioning

confidence: 99%

“…Therefore, it is more meaningful to compare the P n anisotropy directions with geodetically measured strain rates rather than velocities [see (40) for a study in which P n anisotropy is used to measure the width of mantle deformation across a Continental Transform]. In my analysis, I use the SKS fast-splitting directions from (34)(35)(36)41) for the Aegean, central and eastern parts of the NAF, eastern Turkey, and Dead Sea Transform, respectively (see Fig. 2).…”

mentioning

confidence: 99%

Crust-mantle mechanical coupling in Eastern Mediterranean and Eastern Turkey

Özeren

2012

Proc. Natl. Acad. Sci. U.S.A.

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Present-day crust-mantle coupling in the Eastern Mediterranean and eastern Turkey is studied using the Global Positioning System (GPS) and seismic anisotropy data. The general trend of the shear wave fast-splitting directions in NE Turkey and Lesser Caucaus align well with the geodetic velocities in an absolute plate motion frame of reference pointing to an effective coupling in this part of the region of weak surface deformation. Farther south, underneath the Bitlis Suture, however, there are significant Pn delays with E-W anisotropy axes indicating significant lateral escape. Meanwhile, the GPS reveals very little surface deformation. This mismatch possibly suggests a decoupling along the suture. In the Aegean, the shear wave anisotropy and the Pn anisotropy directions agree with the extensional component of the right-lateral shear strains except under the Crete Basin and other parts of the southern Aegean Sea. This extensional direction matches perfectly also with the southward pulling force vectors across the Hellenic trench; however, the maximum right-lateral shear directions obtained from the GPS data in the Aegean do not match either of these anisotropies. Seismic anisotropy from Rayleigh waves sampled at 15 s, corresponding to the lower crust, match the maximum right-lateral maximum shear directions from the GPS indicating decoupling between the crust and the mantle. This decoupling most likely results from the lateral variations of the gravitational potential energies and the slab-pull forces.

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“…In the Southern Aegean, anisotropy is present as indicated by shear wave splitting (e.g. Hatzfeld et al 2001; Evangelidis et al 2011). If S ‐wave splitting occurs a further increase of the CF is observed when the second S wave arrives.…”

Section: Application To Egelados Datamentioning

confidence: 99%

Automated determination of S-phase arrival times using autoregressive prediction: application to local and regional distances

Küperkoch

Meier

Brüstle

et al. 2011

Geophysical Journal International

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S U M M A R YWe present an algorithm for automated S-phase arrival time determination of local, regional and teleseismic events based on autoregressive (AR) prediction of the waveform. The waveforms of the horizontal components are predicted using a scalar AR model for multicomponent recordings. The AR coefficients are estimated in a short moving window using a least-squares approach minimizing the forward prediction error. Synthetic tests with single-component data show that the least-squares approach yields similar or even better results than the Yule-Walker and Burg's algorithms. We discuss the choice of the AR model and show that the corresponding prediction error of the AR model, applied to both horizontal components, is sufficient to detect instantaneous changes in amplitude, frequency, phase and polarization. The rms prediction error of both horizontal components defines the characteristic function, to which an algorithm for the estimation of the arrival time is applied. The proposed algorithm also accounts for automatic quality assessment of the estimated S-onset times. Four quality criteria are used to define the weight of the automatically estimated S-arrival time. They are based on two different estimations of the slope of the characteristic function and on two signal-to-noise ratios (SNRs).The proposed algorithm is applied to a large data set recorded by a dense regional seismic network in the southern Aegean. The data set contains recordings of local and regional crustal as well as intermediate deep earthquakes. The reliability and the robustness of the picking algorithm is tested by comparing more than 2600 manual S readings, serving as reference picks, with the corresponding automatically derived S-onset times. We find an average deviation from the reference picks of 0.5 s ± 0.8 s. If only excellent automatic picks are considered, the average difference from the reference picks is reduced to −0.057 s ± 0.12 s. The proposed automatic quality weighting scheme yields similar weights for the individual S onsets as the ones set by the analysts. The presented algorithm works reliably and robust even when applied to a data set with heterogeneous SNRs. Furthermore, the proposed method may be suitable for the implementation in an earthquake early-warning system as additional, accurate S-wave arrival time estimates stabilize the location, especially the determination of the event depth.

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Shear wave anisotropy beneath the Aegean inferred from SKS splitting observations

Cited by 41 publications

References 53 publications

The dynamics of laterally variable subductions: laboratory models applied to the Hellenides

The dynamics of laterally variable subductions: laboratory models applied to the Hellenides

Crust-mantle mechanical coupling in Eastern Mediterranean and Eastern Turkey

Automated determination of S-phase arrival times using autoregressive prediction: application to local and regional distances

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