Depth variations of the 410 and 520 km‐discontinuities beneath Asia and the Pacific from PP precursors

Schäfer, J.; Rümpker, Georg

doi:10.1029/2009gl038374

Cited by 3 publications

(4 citation statements)

References 17 publications

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“…The detailed structure of the 410 beneath Changbai has rarely been discussed in the previous RF studies, but the 410 is as important as the 660 to speculate mantle dynamics and the origin of intraplate volcanism. The average depth of the 410 is estimated to be ~417 km in our study area, being consistent with the previous studies [ Flanagan and Shearer , ; Schäfer et al , ], which is much deeper than the global average (410 km). Figure shows P wave tomographic images along five vertical cross sections passing through the Changbai volcano.…”

Section: Discussionsupporting

confidence: 93%

“…Hence, we infer that the 520 uplift is related to the cold subducting slab. A number of studies have investigated the 520, and it is generally believed that the 520 is caused by the transition of β-olivine to γ-spinel in the MTZ, and its Clapeyron slope is about 4 MPa/K; the 520 is more sensitive to temperature changes than the 410 and the 660, and so the 520 would exhibit a prominent uplift around the subducting slab [e.g., Ringwood, 1969;Jeanloz and Thompson, 1983;Ito and Takahashi, 1989;Duffy and Anderson, 1989;Shearer, 1990;Deuss and Woodhouse, 2001;Sinogeikin et al, 2003;Schäfer et al, 2009]. A ~20 km uplift of the 520 may reflect a negative thermal anomaly of ~350 K. A previous tomographic study revealed a high-V anomaly of ~3% at 520 km depth beneath the present study region [Zhao and Tian, 2013], which is large enough to cause the 520 uplift detected by our RF study.…”

Section: Discussionmentioning

confidence: 99%

“…Compared with the case of N = 0 (Figure 4b), Figure 4c exhibits a good resolution and clearly shows variations of the discontinuities. Although the cases with N = 2 (Figure 4d) and N = 3 (Figure 4e) exhibit clearer and sharper phases, the converted phase at the 520 and a possible phase related to the upper boundary of the subducting slab are suppressed, which can also provide important information on the MTZ structure [e.g., Li and Yuan, 2003;Schäfer et al, 2009;Shen and Zhou, 2009]. Considering these test results, we chose the case N = 1, because it ensures a good resolution and detection of other meaningful phases.…”

Section: Phase Weighted Stackingmentioning

confidence: 99%

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Mantle transition zone structure beneath the Changbai volcano: Insight into deep slab dehydration and hot upwelling near the 410 km discontinuity

et al. 2016

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We study the detailed mantle transition zone structure beneath the active Changbai intraplate volcano in Northeast China by using a receiver‐function method. A total of 3005 teleseismic receiver functions recorded by 70 broadband stations are obtained by using a common‐conversion‐point stacking method. For conducting the time‐to‐depth conversion, we use a three‐dimensional velocity model of the study region so as to take into account the influence of structural heterogeneities. Our results reveal significant depth variations of the 410, 520, and 660 km discontinuities. A broad depression of the 410 km discontinuity and a low‐velocity anomaly are revealed beneath the Changbai volcano, which may reflect a large‐scale hot mantle upwelling around the 410 km discontinuity with a positive Clapeyron slope. The 520 km discontinuity is identified clearly, and its uplift occurs above the stagnant Pacific slab. We also find a prominent depression of the 660 km discontinuity, which is elongated along the trend of deep earthquake clusters in a range of 39°N–44°N latitude, and the depression area has a lateral extent of about 400 km. Because the 520 and 660 km discontinuities correspond to positive and negative Clapeyron slopes, respectively, we think that the 520 uplift and the 660 depression are caused by the cold subducting Pacific slab. A part of the Pacific slab may have penetrated into the lower mantle and so caused the large‐scale 660 depression in front of the deep earthquake clusters. Our results also reveal a part of the upper boundary of the subducting Pacific slab in the mantle transition zone.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Section: Phase Weighted Stackingmentioning

confidence: 99%

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Mantle transition zone structure beneath the Changbai volcano: Insight into deep slab dehydration and hot upwelling near the 410 km discontinuity

et al. 2016

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“…Ai et al (2005) observed the 520 in receiver functions in Alaska. Schäfer et al (2009) detected the 520 in PP precursors.…”

Section: Sharpness Of 410 and 660mentioning

confidence: 96%

Deep Earth Structure - Transition Zone and Mantle Discontinuities

Kind

2015

Treatise on Geophysics

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Observation of stagnant slab material in the lower transition zone beneath the Aleutian Trench using teleseismic underside reflections

Akoto

Gurrola

2022

Geophysical Journal International

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Summary The goal of this project is to investigate the mantle transition zone across the Aleutian subduction zone using SdS underside reflections. The Aleutian subduction zone is chosen as our study area because of its significant tectonic activity, coupled with high-density data set of SdS midpoints, largely obtained from the US Transportable Array. Seismic images were made using the Wavefield Iterative Deconvolution (WID) stacking method. Our results are corroborated by comparing them with velocity anomalies observed in the 3D GyPSuM Earth Velocity Model. The results of our investigation show that where the subducting Pacific plate passes through the transition zone, the 410 discontinuity is elevated by up to 20 km, and the 660 discontinuity is depressed by up to 40 km. We interpret the variations in the depth to the boundaries of the transition zone (TZ) in terms of Clapeyron slope of the olivine phase changes hypothesized to be responsible for these discontinuities. In this model, the 410 discontinuity is caused by a phase change of olivine to wadsleyite and has a positive Clapeyron slope, while the 660 discontinuity (phase change) represents a phase change of ringwoodite to perovskite and ferropericlase, and has a negative Clapeyron slope. Also, in the transition zone, the 520 discontinuity (a phase change from wadsleyite to ringwoodite) occurs over a 30 km interval, resulting in a boundary that is too gradational to be observed globally in seismic imaging. However, in this study, the 520 is observed in regions close to the cold subducting slab in the Aleutian trench. We suggest this observation is a result of mantle chilling of the lower half of the TZ where the cold subducting Pacific slab does not penetrate the 660 km discontinuity, thereby cooling the mantle beneath the 520. This chilling of the mantle appears to sharpen the velocity contrast at the 520 depth. Finally, we infer that the Pacific slab pools atop the 660 discontinuity and undergoes dehydration that contributes to the observed deepening of the 660.

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Depth variations of the 410 and 520 km‐discontinuities beneath Asia and the Pacific from PP precursors

Cited by 3 publications

References 17 publications

Mantle transition zone structure beneath the Changbai volcano: Insight into deep slab dehydration and hot upwelling near the 410 km discontinuity

Mantle transition zone structure beneath the Changbai volcano: Insight into deep slab dehydration and hot upwelling near the 410 km discontinuity

Deep Earth Structure - Transition Zone and Mantle Discontinuities

Observation of stagnant slab material in the lower transition zone beneath the Aleutian Trench using teleseismic underside reflections

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