A Method for First-Order Earthquake Depth Estimation Using Superarrays

Tibuleac, I. M.

doi:10.1785/0220130212

Cited by 2 publications

(4 citation statements)

References 16 publications

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“…Using autocorrelation to extract depth phase energy is not new and has been applied elsewhere for depth relocation with data from stations at both local and teleseismic distances (e.g., Audet & Ma, ; Tibuleac, ; Zhang et al, ). One of the main differences with our method is that we apply spectral broadening to increase the high‐frequency content and facilitate depth phases detection.…”

Section: Methodsmentioning

confidence: 99%

“…In contrast, our method based on P wave autocorrelation (with move-out correction using the initial depth of 111.3 km to a reference distance of 70 • ) shows clearly the arrival of energy associated with the pP and sP phases, although sP phase is weaker than pP (more about this later). The first 60 s of 400 randomly selected autocorrelograms ( Figure 1c Using autocorrelation to extract depth phase energy is not new and has been applied elsewhere for depth relocation with data from stations at both local and teleseismic distances (e.g., Audet & Ma, 2018;Tibuleac, 2014;Zhang et al, 2014). One of the main differences with our method is that we apply spectral broadening to increase the high-frequency content and facilitate depth phases detection.…”

Section: Validation With a M W 45 Intermediate-depth Earthquake In Nmentioning

confidence: 99%

“…We also calculate the differential arrival time between sP and pP to characterize the Poisson's ratio around the source region to constrain the effect of dehydration. Similar to Tibuleac () and Audet and Ma (), our method relies on autocorrelation to align the

P

wave, but we adopt a spectral broadening scheme to normalize the contribution of different frequency contents, which turns out to have a critical influence on the final results. Since the arrival time of depth phases changes more slowly with respect to epicentral distance than to depth, we can stack the autocorrelograms coherently with a simple move‐out correction, thus greatly increasing the signal‐to‐noise ratio of depth phase energy by using the abundant distribution of broadband seismic stations at teleseismic distances (that is,

normalΔ > 30

°).…”

Section: Introductionmentioning

confidence: 99%

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Earthquake Depth Phase Extraction With P Wave Autocorrelation Provides Insight Into Mechanisms of Intermediate‐Depth Earthquakes

Fang

Hilst

2019

Geophysical Research Letters

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Constraining the mechanism of earthquakes in subduction zones requires adequate estimates of source location and near-source elastic properties. In this study, we propose a P wave autocorrelation-based method to extract depth phase energy from teleseismic earthquakes with moment magnitude down to 4.0. We apply the method to improve location estimates of intermediate-depth earthquakes in the Japan and northern Chile subduction zones, which represent so-called cold and warm slabs, respectively, and which are both marked by double seismic zones. A positive correlation of slab age and double-seismic-zone width validates a thermally controlled model of slab morphology. The negative to normal differential times (and, thus, low or normal Vp/Vs) of the deep parts of the double seismic zones suggest that the intermediate-depth earthquakes considered here are not due to dehydration.Plain Language Summary Earthquake depth, which can be obtained by using depth phases, is critical for hazard mitigation and a better understanding of their mechanisms. Most techniques that use depth phases with teleseismic data require large events, even when array-based techniques are used, which limits comprehensive studies of subduction zone seismicity. Here we propose a new autocorrelation-based method to extract depth phase energy from teleseismic data generated by earthquakes with magnitudes as small as M w 4.0. The application to Japan and northern Chile validates the robustness of the method, and the more precise delineation of the double seismic zones reveals a positive correlation between their widths and the age of the slab when it approaches the trench. Moreover, we find the differential times of sP and pP energy, which are sensitive to the average Vp/Vs between the events and the surface, are different between the upper and the lower layers in the double seismic zone, with the lower layer mostly showing negative to normal values and thus low or normal Vp/Vs. This indicates a lack of water in the lower layer and suggests that other mechanisms are needed to interpret intermediate earthquakes rather than dehydration.

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Section: Methodsmentioning

confidence: 99%

Section: Validation With a M W 45 Intermediate-depth Earthquake In Nmentioning

confidence: 99%

P

normalΔ > 30

°).…”

Section: Introductionmentioning

confidence: 99%

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Earthquake Depth Phase Extraction With P Wave Autocorrelation Provides Insight Into Mechanisms of Intermediate‐Depth Earthquakes

Fang

Hilst

2019

Geophysical Research Letters

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“…The pP depth phase is a wave that goes straight up from the event and is reflected at the free surface. The time difference pP‐P is extremely sensitive to depth [ Bondár and Storchak , ; Engdahl et al , ; Tibuleac , ]. To illustrate this fact we perform theoretical calculations of travel times for two events located at depths of 150 km and 140 km, respectively.…”

Section: Double Difference Relocation Using Depth Phasesmentioning

confidence: 99%

Precise relative earthquake depth determination using array processing techniques

Florez

Prieto

2017

JGR Solid Earth

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Precise determination of hypocentral depth remains one of the most relevant problems in earthquake seismology. It is well known that using depth phases allows for significant improvement in event depth determination; however, routinely and systematically picking such phases, for teleseismic or regional arrivals, is problematic due to poor signal‐to‐noise ratios around the pP and sP phases. To overcome this limitation, we have taken advantage of the additional information carried by seismic arrays. We use velocity spectral analysis to precisely measure pP‐P times. The individual estimates obtained at different subarrays, for all pairs of earthquakes, are combined using a double‐difference algorithm, in order to precisely map seismicity in regions where it is tightly clustered. We illustrate this method by relocating intermediate‐depth earthquakes in the Nazca subducting plate, beneath northern Chile, where we confirm the existence of a narrowly spaced double seismic zone, previously imaged using a local dedicated deployment. As a second example we relocate the aftershock sequence of the 2014 Mw 7.9 intermediate depth, Rat Islands earthquake, and provide evidence of a subvertical fault plane for the main shock. Finally, we show that the resulting relative depth errors are typically smaller than 2 km.

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A Method for First-Order Earthquake Depth Estimation Using Superarrays

Cited by 2 publications

References 16 publications

Earthquake Depth Phase Extraction With P Wave Autocorrelation Provides Insight Into Mechanisms of Intermediate‐Depth Earthquakes

Earthquake Depth Phase Extraction With P Wave Autocorrelation Provides Insight Into Mechanisms of Intermediate‐Depth Earthquakes

Precise relative earthquake depth determination using array processing techniques

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