Investigation of Effects of Near-Surface Complexities on Measurement of Mantle Discontinuity Using SS and Its Precursors

Wang, Peifeng1,2; Zhou, Yong1,3,4; Xu, Min1,3,4; Zhang, Han5; Chen, Xiaofei3,6; Guo, Laiyin7

2022-09-01

10.1029/2022JB024485

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH   Impact Factor & Quartile

2169-9313

2169-9356

["Seismic observations of the mantle discontinuities at depths of 410 and 660 km provide crucial information to constrain the thermal and compositional states and further shape our understanding of mantle dynamics. The topography and impedance contrast of the mantle discontinuities, at both global and regional scales, have been imaged through differential travel times and amplitude ratios between SS and its precursors. However, a relatively simple reference phase (SS) is often assumed, which may overlook potential bias caused by near-surface complexities. To assess these effects, we developed an algorithm to simulate the waveforms of SS and its precursors efficiently based on the propagation matrix method. We found that the crustal thickening increases the differential travel times but does not change the amplitude ratios much, while the sedimentary layer significantly affects both the differential travel times and amplitude ratios. The global anomalies of differential travel times and amplitude ratios are mapped incorporating earth models from CRUST1.0 and PREM. The time shift can reach similar to 9 s, which will bring a depth bias of mantle discontinuity of more than 20 km, while the amplitude ratio anomaly is up to similar to 40%, which will make the impedance contrast of the mantle discontinuity overestimated. The near-surface complexities cannot be ignored in the investigation of mantle discontinuities with SS precursors, especially when the bounce points located in the regions with sediment.","Plain Language Summary The mantle discontinuities at depths of 410 and 660 km define the top and bottom of the mantle transition zone, and act as the phase transition boundaries of major mantle minerals. Investigation of their topography and physical state, which could be distorted by a cold subducting slab or a hot mantle plume, is important to understand the mantle dynamics. At both global and regional scales, the mantle discontinuities have been imaged by differential travel times and amplitude ratios between SS wave and its precursors, and the SS phase reflected at the surface while the precursors reflected at the depth of mantle discontinuities. However, existing studies often assumed a relatively simple reference phase that neglected the effects of near-surface complexities. In this paper, we developed an effective algorithm for simulating SS and its precursors accurately, and quantified the effects of near-surface complexities on the measurement of the differential travel times and amplitude ratios. We found that the near-surface complexities cannot be ignored in SS precursors studies."]

SCI

English

NI Journal Papers

Others

National Natural Science Foundation of China["91858207","42104104"] ; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou)[GML2019ZD0205] ; CAS Key Laboratory of Ocean and Marginal Sea Geology[OMG2020-03] ; Guangdong NSF["2021B1515020023","2017A030312002"] ; K.C. Wong Education Foundation[GJTD-2018-13] ; Ministry of National Science and Technology of China[2018FY100505] ; Chinese Academy of Sciences["Y4SL021001","QYZDY-SSW-DQC005","133244KYSB20180029"] ; Guangdong Basic and Applied Basic Research Foundation[2020A1515110953]

Geochemistry & Geophysics

Geochemistry & Geophysics

WOS:000859749300001

AMER GEOPHYSICAL UNION

GEOSCIENCES

Web of Science

1.Chinese Acad Sci, South China Sea Inst Oceanol, Key Lab Ocean & Marginal Sea Geol, Guangzhou, Peoples R China
2.Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing, Peoples R China
3.Southern Marine Sci & Engn Guangdong Lab, Guangzhou, Peoples R China
4.CAS HEC, China Pakistan Joint Res Ctr Earth Sci, Islamabad, Pakistan
5.Univ New Mexico, Dept Earth & Planetary Sci, Albuquerque, NM 87131 USA
6.Southern Univ Sci & Technol, Dept Earth & Space Sci, Shenzhen, Peoples R China
7.Southern Univ Sci & Technol, Dept Ocean Sci & Engn, Shenzhen, Peoples R China

Wang, Peifeng,Zhou, Yong,Xu, Min,et al. Investigation of Effects of Near-Surface Complexities on Measurement of Mantle Discontinuity Using SS and Its Precursors[J]. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,2022,127(9).

Wang, Peifeng,Zhou, Yong,Xu, Min,Zhang, Han,Chen, Xiaofei,&Guo, Laiyin.(2022).Investigation of Effects of Near-Surface Complexities on Measurement of Mantle Discontinuity Using SS and Its Precursors.JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,127(9).

Wang, Peifeng,et al."Investigation of Effects of Near-Surface Complexities on Measurement of Mantle Discontinuity Using SS and Its Precursors".JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 127.9(2022).