Accurate hypocentre determination in the seismogenic zone of the subducting Nazca Plate in northern Chile using a combined on-/offshore network

Husen, Stephan; Kissling, Edi; Flueh, Ernst R.; Asch, G.

doi:10.1046/j.1365-246x.1999.00893.x

Cited by 166 publications

(186 citation statements)

References 28 publications

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“…We used first detections from a short-term versus long-term average ratio (STA/LTA) trigger and a grid search algorithm for event association and preliminary locations and then specialized P and S phase pick algorithms on targeted phase windows for an improved set of phase picks, which were jointly inverted for new hypocentres and station-phase terms using a 1D velocity model developed for the Chilean forearc 42 . At each step, quality checks were performed to weed out spurious picks, wrong associations, and false and badly constrained events.…”

Section: Earthquake Catalogue Production and Analysismentioning

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: Earthquake Catalogue Production and Analysismentioning

confidence: 99%

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

Schurr

Asch

Hainzl

et al. 2014

Nature

317

364

View full text Add to dashboard Cite

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“…Predicted S-arrival times are calculated in the regional minimum one-dimensional P-wave model of Diehl et al (2009) divided by a constant V P =V S ratio of 1.70. The corresponding hypocenters are relocated in the same minimum one-dimensional model as described by Kissling (1988) or Husen et al (1999) using only P arrivals. The optimal performance was obtained with the picking parameters summarized in Table 4.…”

Section: Calibration and Test Modementioning

confidence: 99%

Automatic S-Wave Picker for Local Earthquake Tomography

Diehl

Deichmann

Kissling

et al. 2009

Bulletin of the Seismological Society of America

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120

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High-resolution seismic tomography at local and regional scales requires large and consistent sets of arrival-time data. Algorithms combining accurate picking with an automated quality classification can be used for repicking waveforms and compiling large arrival-time data sets suitable for tomographic inversion. S-wave velocities represent a key parameter for petrological interpretation, improved hypocenter determination, as well as for seismic hazard models. In our approach, we combine three commonly used phase detection and picking methods in a robust S-wave picking procedure. Information from the different techniques provides an in situ estimate of timing uncertainty and of the reliability of the automatic phase identification. Automatic picks are compared against manually picked reference picks of selected earthquakes in the Alpine region. The average accuracy of automatic picks and their classification is comparable with the reference picks, although a higher number of picks is downgraded to lower quality classes by the automatic picker. In the production-mode, we apply the picker to a data set of 552 earthquakes in the Alps recorded at epicentral distances ≤ 150 km. The resulting data set includes about 2500 S phases with an upper error bound of 0.27 sec.

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“…Steep Angle and wide angle reflection surveys (ANCORP Working Group, 1999;Lüth, 2000;ANCORP Working Group, 2003) and passive seismological networks PISCO 94 (Gräber and Asch, 1999), CINCA 95 (Husen et al, 1999;Patzig, 2000), ANCORP 96 (Haberland and Rietbrock, 2001;ANCORP Working Group, 2003), PUNA97 (Schurr et al, 1999;Schurr, 2000;Schurr et al, 2003;Schurr and Rietbrock, 2004;Schurr et al, 2006), were operated to obtain receiver function (e.g. Yuan et al, 2000) and local tomographic images (e.g.…”

Section: The Central Andes At 21°s and The Altiplano Plateaumentioning

confidence: 99%

More constraints to determine the seismic structure beneath the Central Andes at 21°S using teleseismic tomography analysis

Heit¹,

Koulakov²,

Asch³

et al. 2008

Journal of South American Earth Sciences

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A set of seismological stations was deployed in the Central Andes region along a ~600 km long profile at 21°S between Chile and Bolivia and operated for a period of almost two years, from March 2002 to January 2004. Here we present the results of the tomographic inversion for P-wave velocity anomalies, based on teleseismic data recorded at the stations. The reliability of the results has been checked by a series of synthetic tests. The tomographic images show high-velocities on the west of the profile that are indicative of cold material from the fore-arc. A low-velocity anomaly is detected at the border between the fore-and the volcanic arc where the Quebrada Blanca seismic anomaly was previously described. This anomaly might be related to the presence of fluids that originate at the cluster of earthquakes at a depth of ~100 km in the subducted plate. A strong low-velocity anomaly is detected beneath the entire Altiplano plateau and part of the Eastern Cordillera, in agreement with previous receiver function results. The Brazilian Shield is thought to be responsible for the strong high-velocity anomaly underneath the Interandean and Subandean regions.

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Accurate hypocentre determination in the seismogenic zone of the subducting Nazca Plate in northern Chile using a combined on-/offshore network

Cited by 166 publications

References 28 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

Automatic S-Wave Picker for Local Earthquake Tomography

More constraints to determine the seismic structure beneath the Central Andes at 21°S using teleseismic tomography analysis

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