scholarly journals Explosion study of the structure and seismic velocity distribution of the crust and upper mantle under the Xizang (Tibet) Plateau

1987 ◽  
Vol 89 (1) ◽  
pp. 405-414 ◽  
Author(s):  
Ji-wen Teng
Keyword(s):  
Velocity Distribution ◽  
Upper Mantle ◽  
Seismic Velocity ◽  
Tibet Plateau ◽  
Crust And Upper Mantle

Quaternary sodic and potassic intraplate volcanism in northeast China controlled by the underlying heterogeneous lithospheric structures

Geology ◽  
2021 ◽  
Author(s):  
Xingli Fan ◽  
Qi-Fu Chen ◽  
Yinshuang Ai ◽  
Ling Chen ◽  
Mingming Jiang ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Northeast China ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Subcontinental Lithospheric Mantle ◽  
Seismic Velocities ◽  
S Wave ◽  
Crust And Upper Mantle ◽  
Potassic Volcanism

The origin and mantle dynamics of the Quaternary intraplate sodic and potassic volcanism in northeast China have long been intensely debated. We present a high-resolution, three-dimensional (3-D) crust and upper-mantle S-wave velocity (Vs) model of northeast China by combining ambient noise and earthquake two-plane wave tomography based on unprecedented regional dense seismic arrays. Our seismic images highlight a strong correlation between the basalt geochemistry and upper-mantle seismic velocity structure: Sodic volcanoes are all characterized by prominent low seismic velocities in the uppermost mantle, while potassic volcanoes still possess a normal but thin upper-mantle “lid” depicted by high seismic velocities. Combined with previous petrological and geochemical research findings, we propose that the rarely erupted Quaternary potassic volcanism in northeast China results from the interaction between asthenospheric low-degree melts and the overlying subcontinental lithospheric mantle. In contrast, the more widespread Quaternary sodic volcanism in this region is predominantly sourced from the upwelling asthenosphere without significant overprinting from the subcontinental lithospheric mantle.

scholarly journals Seismic Velocity Structure in the Crust and Upper Mantle beneath Northern Japan.

1994 ◽  
Vol 42 (4) ◽  
pp. 269-301 ◽  
Author(s):  
Hiroki Miyamachi ◽  
Minoru Kasahara ◽  
Sadaomi Suzuki ◽  
Kazuo Tanaka ◽  
Akira Hasegawa
Keyword(s):  
Upper Mantle ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Crust And Upper Mantle ◽  
Seismic Velocity Structure ◽  
Northern Japan

Electrical properties of the lithosphere in the western desert, Egypt, using magnetotelluric sounding

2021 ◽  
Author(s):  
Hossam Marzouk ◽  
Tarek Arafa-Hamed ◽  
Michael Becken ◽  
Mohamed Abdel Zaher ◽  
Matthew Comeau
Keyword(s):  
Upper Mantle ◽  
Seismic Velocity ◽  
Western Desert ◽  
Velocity Data ◽  
Profile Data ◽  
Crust And Upper Mantle ◽  
Near Surface ◽  
The Earth ◽  
Nubian Aquifer ◽  
Dakhla Oasis

<p>We present electrical resistivity models of the crust and upper mantle estimated from 2D inversions of broadband magnetotellurics (MT) data acquired from two profiles in the western desert of Egypt, which can contribute to the understanding of the structural setup of this region. The first profile data are collected from 14 stations along a 250 km profile, in EW direction profile runs along latitude ~25.5°N from Kharga oasis to Dakhla oasis. The second profile comprises 19 stations measured along a 130 km profile in NS direction centered at longitude 28°E and crossing the Farafra. The acquisition for both profiles continued for 1 to 3 days at each station, which allowed for the calculation of impedances for periods from 0.01 sec up to  4096 sec at some sites. The wide frequency band corresponds to a maximal skin depths of up to 150 km that can provide penetration to the top of the asthenosphere. The inversion models display high-conductivity sediments cover at the near surface (<1-2 km), which can be associated with the Nubian aquifer. Along the EW-profile from Kaharge to Dhakla, the crustal basement is overly highly resistive and homogeneous und underlain by a more conductive lithospheric mantle below depths of 30-40 km. Along the N-S profile across Farafra, only the southern portion exhibits a highly resistive crust, whereas beneath Farafra northwards, moderate crustal conductivities are encountered. A comparison has been made between the resultant resistivity models with the 1° tessellated updated crust and lithospheric model of the Earth (LITHO1.0) which was developed by <em>Pasyanos, 2014</em> on the basis of seismic velocity data. The obtained results show a remarkable consistency between the resistivity models and the calculated crustal boundaries. Especially at the Kharga-Dakhla profile a clear matching can be noticed at the upper and lower boundaries of a characteristic anomaly with the Moho and LAB boundaries respectively.</p>

Lateral inhomogeneities in P velocity under the Tarbela array of the lesser Himalayas of Pakistan

1977 ◽  
Vol 67 (3) ◽  
pp. 725-734
Author(s):  
William H. Menke
Keyword(s):  
Travel Time ◽  
Upper Mantle ◽  
Lower Crust ◽  
Seismic Velocity ◽  
Three Dimensional ◽  
Horizontal Layer ◽  
Main Central Thrust ◽  
Crust And Upper Mantle ◽  
Lesser Himalayas ◽  
Velocity Anomalies

abstract Three-dimensional seismic-velocity heterogeneities (to a depth of 125 km) under the Tarbela array are determined by the Aki et al. (1976a) method of inverting teleseismic travel-time residuals. Velocity anomalies are clearly present and are elongated in the northwest direction. An overall 2 to 3 per cent decrease in velocity to the northeast is observed across any horizontal layer. These features result from a 4° dip of geologic structures in the direction N41°E. This direction is similar to some observed trends of seismicity in the Tarbela area and to the trend of the Himalayan Main Central Thrust (MCT) east and north of Tarbela, but not to the trend of the fault traces nor the strike of geologic structures in the Tarbela area. Just to the southeast of the Tarbela array, these faults bend sharply westward, forming a mountainous loop. In this study it is concluded that the westerly trending fault traces and westerly striking geology are both only surficial and not representative of structures at greater depth. These deep structures within the lower crust and upper mantle preserve a strike similar to more eastern areas along the MCT. They are shown to be volumetrically and tectonically the more important features.

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