Semblance and Other Coherency Measures for Multichannel Data

Neidell, Norman S.; Taner, M. Turhan

doi:10.1190/1.1440186

Cited by 752 publications

(409 citation statements)

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“…We have measured the coherence between the traces by semblance 10,35 , which is a normalized version of the stacked energy and ranges in the interval [0-1], where S=1 signifies perfectly coherent signals. Semblance and energy at the i-th grid point in the source area are defined as follows:…”

Section: Backprojectionmentioning

confidence: 99%

Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake

Schurr

Asch

Hainzl

et al. 2014

Nature

318

364

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Several major earthquakes (Mw>7) have occurred in this gap since 1850 (Fig. 1); the largest until now was the Mw 7.7 Tocopilla earthquake in 2007, which broke the southern rim of this segment beneath and north of Mejillones Peninsula along a total length of 150 km. Only the downdip end of the locked zone slipped in this event, and the total slip in the rupture area was less than 2.6 m 6,7 leaving most of the past slip deficit of c. 8-9 m accumulated since 1877 3 approaches. First, we performed waveform modelling of local strong motion seismograms and teleseismic body waves to constrain the kinematic development of the rupture towards the final displacement in a joint inversion with continuous GPS data of static displacements (Fig. 1, 2a). Second, we use the backprojection technique applied to stations in North America to map the radiation of high frequency seismic waves (HFSR; 1-4 Hz) 9,10 . The latter technique is not sensitive to absolute slip amplitudes, but rather to changes in slip and rupture velocity.During the first 35-40s the rupture propagated downdip with increasing velocity, nearly reaching the coastline (Fig. 2a,b). Surprisingly, towards the end of the rupture, the area near the epicenter was reactivated. In spite of the relatively complicated kinematic history of the rupture the cumulative slip shows a simple 'bull's eye' pattern with a peak coseismic slip of (Fig. 3a). The Iquique main shock nucleated at the 4 northwestern border of a locked patch and ruptured towards its center (Fig. 2a, 3a). The downdip end of the main shock as well as for the large Mw 7.6 aftershock rupture mapped both by the HFSR and co-seismic slip agrees quite accurately with the downdip end interseismic coupling (Fig. 2a,c 3a). The accelerated downdip rupture propagation for both earthquakes closely followed the gradient towards higher locking. Therefore, the Iquique event and its largest aftershock appear to have broken the central, only partly locked segment of the Northern Chile Southern Peru seismic gap releasing part of the slip deficit accumulated here since 1877 (cf. Fig. 1).The seismicity before the Iquique earthquake also concentrates in this zone of intermediate locking at the fringe of the highly locked -high slip patch (Fig. 3a). Starting in July 2013, three foreshock clusters with increasingly larger peak magnitudes and cumulative seismic moment occurred here (Fig. 2c, 3a,c). The mainshock rupture started at the northern end of the foreshock zone, inside the region of intermediate locking (Fig. 2c, 3a). Interestingly, the second foreshock cluster (January 2014) is associated with a weak transient deformation, whereas the third cluster (March 2014) shows a very distinct transient signal. GPS displacement vectors calculated over the times spanning these foreshock clusters point towards the cluster epicentres (Extended Data Figure 4). Deformation for both transients is entirely explained by the cumulative coseismic displacement of the respective foreshock clusters (Fig. 3d inset, Extended Data Figure 4). The ar...

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Section: Backprojectionmentioning

confidence: 99%

Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake

Schurr

Asch

Hainzl

et al. 2014

Nature

318

364

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“…4). The data quality monitoring then included evaluation of the classical ambient vibration H/V ratio (Nakamura 1989;SESAME team 2004;Bard et al 2010) (Fig. 4).…”

Section: Acquisition Layoutmentioning

confidence: 99%

Characterization of site conditions (soil class, VS30, velocity profiles) for 33 stations from the French permanent accelerometric network (RAP) using surface-wave methods

Hollender

Cornou

Dechamp

et al. 2017

Bull Earthquake Eng

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Data provided by accelerometric networks are important for seismic hazard assessment. The correct use of accelerometric signals is conditioned by the station site metadata quality (i.e., soil class, V S30 , velocity profiles, and other relevant information that can help to quantify site effects). In France, the permanent accelerometric network consists of about 150 stations. Thirty-three of these stations in the southern half of France have been characterized, using surface-wave-based methods that allow derivation of velocity profiles from dispersion curves of surface waves. The computation of dispersion curves and their subsequent inversion in terms of shear-wave velocity profiles has allowed estimation of V S30 values and designation of soil classes, which include the corresponding uncertainties. From a methodological point of view, this survey leads to the following recommendations: (1)

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“…However, dense networks of broadband receivers with station separation representing a fraction of the wavelength of VLP energy allow measurements of the coherence of VLP signals, and a derivation of source locations. To locate the VLP sources we use the semblance method [Neidell and Taner, 1971] extended to account for rectilinearity by Kawakatsu et al [2000]. Now called Radial Semblance (RS), this technique is well suited to calculating the source location of VLP signals.…”

Section: Introductionmentioning

confidence: 99%

Application of near real‐time radial semblance to locate the shallow magmatic conduit at Kilauea Volcano, Hawaii

Dawson

Whilldin²,

Chouet

2004

Geophysical Research Letters

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[1] Radial Semblance is applied to broadband seismic network data to provide source locations of Very-LongPeriod (VLP) seismic energy in near real time. With an efficient algorithm and adequate network coverage, accurate source locations of VLP energy are derived to quickly locate the shallow magmatic conduit system at Kilauea Volcano, Hawaii. During a restart in magma flow following a brief pause in the current eruption, the shallow magmatic conduit is pressurized, resulting in elastic radiation from various parts of the conduit system. A steeply dipping distribution of VLP hypocenters outlines a region extending from sea level to about 550 m elevation below and just east of the Halemaumau Pit Crater. The distinct hypocenters suggest the shallow plumbing system beneath Halemaumau consists of a complex plexus of sills and dikes. An unconstrained location for a section of the conduit is also observed beneath the region between Kilauea Caldera and Kilauea Iki Crater.

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Semblance and Other Coherency Measures for Multichannel Data

Cited by 752 publications

References 0 publications

Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake

Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake

Characterization of site conditions (soil class, VS30, velocity profiles) for 33 stations from the French permanent accelerometric network (RAP) using surface-wave methods

Application of near real‐time radial semblance to locate the shallow magmatic conduit at Kilauea Volcano, Hawaii

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