Joint Epicentre Determination

Douglas, A.

doi:10.1038/215047a0

Cited by 344 publications

(159 citation statements)

References 1 publication

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“…[41] It is difficult to interpret the station corrections computed in our JHDME inversions although it is shown that these corrections (and station residuals) correlate well with velocity variations, [Douglas, 1967;Toy, 1989; Pujol, Figure 7. The top panel shows the mantle P wave perturbations to P12 [Su and Dziewonski, 1993] after inverting about 70,000 relocated phases of the 1500 master events.…”

Section: Station Correctionsmentioning

confidence: 99%

“…[28] Detailed comparison of our method with other cluster relocation techniques (i.e., SER coupled with 3D mantle correction (SER3D) [Antolik et al, 2001], JHD [Douglas, 1967;Pavlis and Booker, 1983;Pujol, 1992], Hypocentroid Decomposition (HDC) [Jordan and Sverdrup, 1981], Double Difference (DD) [Waldhauser and Ellsworth, 2000] …”

Section: Jhdme With Single Master Eventmentioning

confidence: 99%

“…[46] JHD is an extension of the method first proposed by Douglas [1967] to relocate closely clustered earthquakes together with station corrections, to account for the inaccuracies of the Earth model, station response, and source mechanisms.…”

Section: Appendix B: Joint Hypocenter Determination (Jhd)mentioning

confidence: 99%

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Locations of mid‐oceanic earthquakes constrained by seafloor bathymetry

2002

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[1] Earthquakes associated with the creation of new oceanic crust are difficult to locate precisely because they normally occur far away from seismic stations. We assume that epicenters of these events can be constrained by seafloor topography and use the Harvard centroid moment tensor (CMT) focal mechanism of an interplate earthquake to relate the event to either a transform fault (a parallel in a coordinate system defined by the pole of rotation between two plates) or a mid-oceanic ridge (a meridian). Using arrival times from the International Seismological Center (ISC) Bulletin, we have relocated about 1500 globally distributed events for the time period 1976-1998. The ISC locations can be as much as 70 km away from appropriate topographic features. Our new locations support that large interplate earthquakes occur on or very close to the primary bathymetric features. For earthquakes with unknown mechanism or magnitude below the CMT threshold or predate the CMT catalog, we use a simultaneous Joint Hypocenter Determination procedure with respect to the already relocated Master Events (JHDME). We invert for earthquakes first for the Romanche Fracture Zone (RFZ) and then for a region extending from 30°N to 30°S. Seismicity agrees well with the main active ridge or transform. However, a small number of events might be related to the secondary bathymetry features. The improved locations for mid-oceanic earthquakes based on bathymetry could help improve our understanding of the oceanic crustal and deep Earth structure, seismic slip and budget constraint along plate boundaries, and dynamics of plate tectonics.

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Section: Station Correctionsmentioning

confidence: 99%

Section: Jhdme With Single Master Eventmentioning

confidence: 99%

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Locations of mid‐oceanic earthquakes constrained by seafloor bathymetry

2002

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“…There are several variants of this method (see, e.g., Waldhauser and Ellsworth 2000;Rudzinski and Debski 2012;Douglas 1967). In oint event location, events are relocated according to the location of the so-called ''master event'' (Douglas 1967). Relative location methods usually improve the accuracy of source location; however, they are strongly influenced by data quality, similarly to non-relative methods of location (Rudzinski and Debski 2011;Debski and Klejment 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Another method is the relative location method, for which the location of the source is determined relative to the location of adjacent sources. There are several variants of this method (see, e.g., Waldhauser and Ellsworth 2000;Rudzinski and Debski 2012;Douglas 1967). In oint event location, events are relocated according to the location of the so-called ''master event'' (Douglas 1967).…”

Section: Introductionmentioning

confidence: 99%

Time reversal seismic source imaging using peak average power ratio (PAPR) parameter

2017

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The time reversal method has become a standard technique for the location of seismic sources. It has been used both for acoustic and elastic numerical modelling and for 2D and 3D propagation models. Although there are many studies concerning its application to point sources, little so far has been done to generalise the time reversal method to the study of sequences of seismic events. The need to describe such processes better motivates the analysis presented in this paper. The synthetic time reversal imaging experiments presented in this work were conducted for sources with the same origin time as well as for the sources with a slight delay in origin time. For efficient visualisation of the seismic wave propagation and interference, a new coefficient-peak average power ratiowas introduced. The paper also presents a comparison of visualisation based on the proposed coefficient against a commonly used visualisation based on a maximum value.

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Investigation of Backprojection Uncertainties With M6 Earthquakes

Fan

Shearer

2017

JGR Solid Earth

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We investigate possible biasing effects of inaccurate timing corrections on teleseismic P wave backprojection imaging of large earthquake ruptures. These errors occur because empirically estimated time shifts based on aligning P wave first arrivals are exact only at the hypocenter and provide approximate corrections for other parts of the rupture. Using the Japan subduction zone as a test region, we analyze 46 M6–M7 earthquakes over a 10 year period, including many aftershocks of the 2011 M9 Tohoku earthquake, performing waveform cross correlation of their initial P wave arrivals to obtain hypocenter timing corrections to global seismic stations. We then compare backprojection images for each earthquake using its own timing corrections with those obtained using the time corrections from other earthquakes. This provides a measure of how well subevents can be resolved with backprojection of a large rupture as a function of distance from the hypocenter. Our results show that backprojection is generally very robust and that the median subevent location error is about 25 km across the entire study region (∼700 km). The backprojection coherence loss and location errors do not noticeably converge to zero even when the event pairs are very close (<20 km). This indicates that most of the timing differences are due to 3‐D structure close to each of the hypocenter regions, which limits the effectiveness of attempts to refine backprojection images using aftershock calibration, at least in this region.

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Joint Epicentre Determination

Cited by 344 publications

References 1 publication

Locations of mid‐oceanic earthquakes constrained by seafloor bathymetry

Locations of mid‐oceanic earthquakes constrained by seafloor bathymetry

Time reversal seismic source imaging using peak average power ratio (PAPR) parameter

Investigation of Backprojection Uncertainties With M6 Earthquakes

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