Traveltimes for global earthquake location and phase identification

Kennett, B. L. N.; Engdahl, E. R.

doi:10.1111/j.1365-246x.1991.tb06724.x

Cited by 3,194 publications

(2,347 citation statements)

References 15 publications

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“…In this modelling scheme the surface displacements due to subduction are modelled as dislocations (backslips) on the plate interface, with regions of largest modelled dislocation interpreted as being the most locked regions. For forward modelling, we use a layered elastic half space and IASP Earth model 38 .…”

Section: Interseismic Lockingmentioning

confidence: 99%

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

Schurr

Asch

Hainzl

et al. 2014

Nature

317

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: Interseismic Lockingmentioning

confidence: 99%

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

Schurr

Asch

Hainzl

et al. 2014

Nature

317

364

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“…8(a) (Bassin et al 2000) over IASP91 (Kennett & Engdahl 1991) for the mantle structure (black) and Savage & Wang's model (2012, red). In the left-hand panel, the obtained (solid) shear wave velocities versus depth are plotted with respect to the initial models (dashed).…”

Section: Methodsmentioning

confidence: 99%

Seismic structure beneath the Gulf of California: a contribution from group velocity measurements

Luccio

Persaud

Clayton

2014

Geophysical Journal International

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“…Table 1 Basic information about the eight wells that have resolvable tidal responses, as well as the theoretical and actual initial response times of the water level to the M w 7.9 Wenchuan earthquake that happened on May 12, 2008 at 14:28 local time. We assume the initial response is coincident with the P-waves, calculate the travel times for the P wave by the IASP91 model (Kennett and Engdahl, 1991), and make clock corrections as necessary.…”

Section: Tidal Response Methodsmentioning

confidence: 99%

Tidal response variation and recovery following the Wenchuan earthquake from water level data of multiple wells in the nearfield

Lai

Xue

et al. 2014

Tectonophysics

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An important dataset to emerge from the Wenchuan earthquake Fault Scientific Drilling project is direct measurement of the permeability evolution of a fault zone. In order to provide context for this new observation, we examined the evolution of tidal responses in the nearfield region (within~1.5 fault lengths) at the time of the mainshock. Previous work has shown that seismic waves can increase permeability in the farfield, but their effects in the nearfield are more difficult to discern. Close to an earthquake, hydrogeological responses are generally a combination of static and dynamic stresses. In this work, we examine the well water level data in the region of the large M w 7.9 Wenchuan earthquake and use the phase shift of tidal responses as a proxy for the permeability variations over time. We then compare the results with the coseismic water level pattern in order to separate out the dynamic and static effects. The coseismic water level pattern for observed steps coincident with the Wenchuan mainshock mainly tracks the expected static stress field. However, most of the wells that have resolvable tidal responses show permeability enhancement after this large earthquake regardless of whether the coseismic response for the well water level is increasing or decreasing, indicating permeability enhancement is a distinct process from static poroelastic strain.

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Traveltimes for global earthquake location and phase identification

Cited by 3,194 publications

References 15 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

Seismic structure beneath the Gulf of California: a contribution from group velocity measurements

Tidal response variation and recovery following the Wenchuan earthquake from water level data of multiple wells in the nearfield

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