The Applicability of Modern Methods of Earthquake Location

Richards, Paul G.; Waldhauser, F.; Schaff, D. P.; Kim, Youn-Jung

doi:10.1007/3-7643-7585-x_4

Cited by 21 publications

(24 citation statements)

References 30 publications

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“…31 For example, a regional wave traveling 500 km has a travel time of about 100 seconds. If there is a total 5% error in the velocity model, this corresponds to a location error of 25 km.…”

Section: Location Of Seismic Sourcesmentioning

confidence: 99%

Progress in CTBT Monitoring Since its 1999 Senate Defeat

Hafemeister

2007

Science & Global Security

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“…31 For example, a regional wave traveling 500 km has a travel time of about 100 seconds. If there is a total 5% error in the velocity model, this corresponds to a location error of 25 km.…”

Section: Location Of Seismic Sourcesmentioning

confidence: 99%

Progress in CTBT Monitoring Since its 1999 Senate Defeat

Hafemeister

2007

Science & Global Security

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“…We apply the so-called double-difference techniques (e.g. Waldhauser & Ellsworth 2000;Richards et al 2006) which find the most probable relative event locations by minimizing the residuals between predicted and measured traveltime differences.…”

Section: Introductionmentioning

confidence: 99%

Accurate relative location estimates for the North Korean nuclear tests using empirical slowness corrections

Gibbons¹,

Pabian

Näsholm³

et al. 2016

Geophys. J. Int.

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SUMMARYDeclared North Korean nuclear tests in 2006, 2009, 2013, and 2016 were observed seismically at regional and teleseismic distances. Waveform similarity allows the events to be located relatively with far greater accuracy than the absolute locations can be determined from seismic data alone. There is now significant redundancy in the data given the large number of regional and teleseismic stations that have recorded multiple events, and relative location estimates can be confirmed independently by performing calculations on many mutually exclusive sets of measurements. Using a 1-dimensional global velocity model, the distances between the events estimated using teleseismic P phases are found to be approximately 25% shorter than the distances between events estimated using regional Pn phases. The 2009The , 2013, and 2016 events all take place within 1 km of each other and the discrepancy between the regional and teleseismic relative location estimates is no more than about 150 m. The discrepancy is much more significant when estimating the location of the more distant 2006 event relative to the later explosions with regional and teleseismic estimates varying by many hundreds of meters. The relative location of the 2006 event is challenging given the smaller number of observing stations, the lower signal-to-noise ratio, and significant waveform dissimilarity at some regional 2 S. J. Gibbons et al.stations. The 2006 event is however highly significant in constraining the absolute locations in the terrain at the Punggye-ri test-site in relation to observed surface infrastructure.For each seismic arrival used to estimate the relative locations, we define a slowness scaling factor which multiplies the gradient of seismic traveltime versus distance, evaluated at the source, relative to the applied 1-d velocity model. A procedure for estimating correction terms which reduce the double-difference time residual vector norms is presented together with a discussion of the associated uncertainty. The modified velocity gradients reduce the residuals, the relative location uncertainties, and the sensitivity to the combination of stations used. The traveltime gradients appear to be overestimated for the regional phases, and teleseismic relative location estimates are likely to be more accurate despite an apparent lower precision. Calibrations for regional phases are essential given that smaller magnitude events are likely not to be recorded teleseismically. We discuss

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“…Among network geometry, the power of hypoDD to resolve small structures depends on uncertainties and consistencies of the arrival times. Therefore, cross-correlation measurements are often combined with catalog picks to improve hypoDD locations (e.g., Waldhauser and Ellsworth 2000; Richards et al 2006). This approach requires careful and sophisticated weighting between the two sets of arrival times.…”

Section: Double-difference Hypocenter Locationsmentioning

confidence: 99%

Induced seismicity during the construction of the Gotthard Base Tunnel, Switzerland: hypocenter locations and source dimensions

2011

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A series of 112 earthquakes was recorded between October 2005 and August 2007 during the excavation of the MFS Faido, the southernmost access point of the new Gotthard Base Tunnel. Earthquakes were recorded at a dense network of 11 stations, including 2 stations in the tunnel. Local magnitudes computed from Wood-Anderson-filtered horizontal component seismograms ranged from −1.0 to 2.4; the largest earthquake was strongly felt at the surface and caused considerable damage in the tunnel. Hypocenter locations obtained routinely using a regional 3-D P-wave velocity model and a constant Vp/Vs ratio 1.71 were about 2 km below the tunnel. The use of seismic velocities calibrated from a shot in the tunnel revealed that routinely obtained hypocenter locations were systematically biased to greater depth and are now relocated to be on the tunnel level. Relocation of the shot using these calibrated velocities yields a location accuracy of 25 m in longitude, 70 m in latitude, and 250 m in focal depth. Double-difference relative relocations of two clusters with highly similar waveforms showed a NW-SE striking trend that is consistent with the strike of mapped faults in the MFS Faido. Source dimensions computed using the quasidynamic model of Madariaga (Bull Seismo Soc Am 66 (3): 1976) range from 50 to 170 m. Overlapping source dimensions for earthquakes within the two main clusters suggests that the same fault patch was ruptured repeatedly. The observed seismicity was likely caused by stress redistribution due to the excavation work in the MFS Faido.

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The Applicability of Modern Methods of Earthquake Location

Cited by 21 publications

References 30 publications

Progress in CTBT Monitoring Since its 1999 Senate Defeat

Progress in CTBT Monitoring Since its 1999 Senate Defeat

Accurate relative location estimates for the North Korean nuclear tests using empirical slowness corrections

Induced seismicity during the construction of the Gotthard Base Tunnel, Switzerland: hypocenter locations and source dimensions

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