scholarly journals Constraining the Moho Depth Below Bhutan With Global-Phase Seismic Interferometry

2021 ◽  
Vol 9 ◽  
Author(s):  
Anne Obermann ◽  
Elmer Ruigrok ◽  
Irene Bianchi ◽  
György Hetényi
Keyword(s):  
Receiver Function ◽  
Crustal Thickening ◽  
Seismic Interferometry ◽  
Moho Depth ◽  
Lithospheric Structure ◽  
Correlation Integral ◽  
First Order ◽  
Novel Technique ◽  
Collision Zone ◽  
Orogenic Wedge

We use a novel technique named global-phase seismic interferometry (GloPSI) to image the lithospheric structure, and in particular the Moho, below two parallel north-south transects belonging to the GANSSER network (2013–2014). The profiles cross the Himalayan orogenic wedge in Bhutan, a tectonically important area within the largest continent-continent collision zone on Earth that is still undergoing crustal thickening and represents a challenging imaging target for the GloPSI approach. GloPSI makes use of direct waves from distant earthquakes and receiver-side reverberations with near vertical incidence. Reflections are isolated from earthquake recordings by solving a correlation integral and are turned into a reflectivity image of the lithosphere below the arrays. Our results compare favorably with first-order features observed from a previous receiver function (RF) study. We show that a combined interpretation of GloPSI and RF results allows for a more in-depth understanding of the lithospheric structure across the orogenic wedge in Bhutan.

Sediment Thickness and Moho Depth Beneath Western Indonesian Region From Teleseismic Receiver Function

2021 ◽  
Author(s):  
Syaiful Bahri ◽  
Wiwit Suryanto ◽  
Drajat Ngadmanto
Keyword(s):  
Shear Wave ◽  
Shear Wave Velocity ◽  
Receiver Function ◽  
Velocity Model ◽  
Moho Depth ◽  
Sediment Layer ◽  
The North ◽  
East Kalimantan ◽  
Crust Layer ◽  
Teleseismic Receiver Function

Abstract The Earth's crust layer and sediment in Western Indonesia has been studied using the inversion of teleseismic receiver function from BMKG’s seismic network. Earthquake events were analyzed in this study with a moment magnitude greater than 6.0 with epicentral distances of 30° to 90°. A total of 60 earthquake events were observed and recorded by 91 stations around the study area. Furthermore, an inversion process was carried out using the initial velocity model from the modification of the AK135f velocity model to obtain the shear wave velocity structure below each stations. The velocity model from the azimuthally stacked vertical receiver function showed that the sediment layer had a relatively medium shear wave velocity value with an average of 2.1 km/s, while the crust layer had 4.60 km/s. The sedimentary layer thickness in this region also varies between 2 km to 10 km. A relatively thick sediment layer of about 8 km to 10 km was observed in two locations, in East Kalimantan associated with the Kutai Basin and Northern part of Sumatera in the North Sumatera Basin, a two major oil producer basinal area in Indonesia. The Moho discontinuity was also found at depths that vary between 16 km to 50 km. In addition, the most shallow Moho depth is 16 km below the North Kalimantan and North part of West Java, while the deeper Moho depth of 50 km is located below East Kalimantan, Central Kalimantan, North Sumatera and South Sumatera.

Striking differences in lithospheric structure between the north- and south-western Alps: insights from receiver functions along the Cifalps profiles and a new Vs model

2021 ◽  
Author(s):  
Anne Paul ◽  
Ahmed Nouibat ◽  
Liang Zhao ◽  
Stefano Solarino ◽  
Stéphane Schwartz ◽  
...  
Keyword(s):  
Receiver Function ◽  
Negative Polarity ◽  
Western Alps ◽  
Lithospheric Structure ◽  
Seismic Stations ◽  
Continental Subduction ◽  
The North ◽  
Ligurian Alps ◽  
The Alps ◽  
Converted Waves

<p>The CIFALPS receiver-function (RF) profile in the southwestern Alps provided the first seismological evidence of continental subduction in the Alps, with the detection of waves converted on the European Moho at 75-80 km depth beneath the western edge of the Po basin (Zhao et al., 2015). To complement the CIFALPS profile and enhance our knowledge of the lithospheric structure of the Western Alps, we installed CIFALPS2, a temporary network of 55 broadband seismic stations that operated for ~14 months (2018-2019) across the North-Western Alps (Zhao et al., 2018). The CIFALPS2 line runs from the Eastern Massif Central to the Ligurian coast, across the Mont-Blanc and Gran Paradiso massifs and the Ligurian Alps. Seismic stations were installed along a quasi-linear profile with a spacing of 7-10 km.</p><p>We will show 2 receiver-function CCP (common-conversion point) depth-migrated sections along the CIFALPS2 profile, the first one across the Alps, and the second one across the Ligurian Alps and the Po basin. The time-to-depth migration of RF data is based on the new 3-D Vs model of the Greater Alpine region derived by Nouibat et al. (2021) using transdimensional ambient noise tomography on a large dataset including the AlpArray seismic network. Depth sections across the Vs model are also useful for interpreting the RF CCP sections as they have striking similarities.</p><p>The images of the lithospheric structure of the NW Alps along CIFALPS2 are surprisingly different from those of the SW Alps along CIFALPS. The deepest P-to-S converted phases on the European Moho are detected at 60-65 km depth beneath the Ivrea-Verbano zone, that is 15 km less than on CIFALPS. The negative polarity converted phase interpreted as the base of the Ivrea body mantle flake on the CIFALPS section is still visible on CIFALPS2, but with a lower amplitude. The RF section confirms the existence of a jump of the European Moho of ~10 km amplitude in less than 10 km distance, which is located within a few km from the western boundary of the Mont Blanc external crystalline massif. All these observations are confirmed by the Vs model that also displays a less deep continental subduction than on CIFALPS, weaker S-wave velocities in the Ivrea body wedge, and the jump of the European Moho.</p><p>The Moho beneath the Ligurian Alps is detected at 25-30 km depth both on the RF and on the Vs depth sections. Moving northwards, this Ligurian Moho is separated from the Adriatic Moho by a puzzling S-dipping set of P-to-S converted waves with negative polarity. The crust of the Ligurian Alps is characterized by a set of north-dipping negative-polarity converted waves at 10 to 20 km depth beneath the Valosio massif, which is a small internal crystalline massif of (U)HP metamorphic rocks located north of Voltri. The similarity of this set of negative-polarity conversions to the one observed beneath the Dora Maira massif on the CIFALPS profile suggests that it may be a relic of the Alpine structure overprinted by the opening of the Ligurian sea.</p>

Architecture of the crust and lithosphere beneath the Semail Ophiolite from ambient noise tomography and receiver functions: insights on the tectonic evolution of eastern Arabia

2021 ◽  
Author(s):  
Christian Weidle ◽  
Lars Wiesenberg ◽  
Andreas Scharf ◽  
Philippe Agard ◽  
Amr El-Sharkawy ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Ambient Noise ◽  
Function Analysis ◽  
Oceanic Lithosphere ◽  
Receiver Functions ◽  
Crustal Thickening ◽  
Ambient Noise Tomography ◽  
First Order ◽  
Pan African ◽  
Semail Ophiolite

<p>The Semail Ophiolite is the world<span>‘</span>s largest and best exposed oceanic lithosphere on land and a primary reference site for studies of creation of oceanic lithosphere, initiation of subduction, geodynamic models of obduction, subduction and exhumation of continental rocks during obduction. Five decades of geological mapping, structural, petrological and geochronological research provide a robust understanding of the geodynamic evolution of the shallow continental crust in northern Oman and how the late Cretaceous obduction process largely shaped the present-day landscape. Yet, prior to obduction, other first-order tectonic processes have left their imprint in the lithosphere, in particular the Neoproterozoic accretion of Arabia and Permian breakup of Pangea. Due to the scarcity of deep structure imaging below the ophiolite, the presence and significance of inherited structures for the obduction process remain unclear.</p><p>We discuss a new 3-D anisotropic shear wave velocity model of the crust below northern Oman derived from ambient noise tomography and Receiver Function analysis which allows to <span>resolve</span> some key unknowns in geodynamics of eastern Arabia: (1) <span>Several NE-trending structural boundaries in the middle and lower crust are attributed to the Pan-African orogeny and align with first-order lateral changes in surface geology and topography.</span> (2) The well-known Semail Gap Fault Zone is an upper crustal feature whereas two other deep crustal faults are newly identified. (3) Permian rifting occurred on both eastern and northern margins but large-scale mafic intrusions and/or underplating occurred only in the east. (4) While obduction is inherently lithospheric by nature, its effects <span>are mostly observed at shallow crustal depths, and lateral variations in its geometry and dynamics can be explained by effects on pre-existing Pan-African and Permian structures. (5) Continental subduction and exhumation during late Cretaceous obduction may be the cause for crustal thickening below today‘s topography.</span> (6) Thinning of the continental lithosphere below northern Oman in late Eocene times – possibly related to thermal effects of the incipient Afar mantle plume - provides a plausible mechanism for the broad emergence of the Oman Mountains and in particular the Jabal Akhdar Dome. Uplift might thus be unrelated to compressional tectonics during Arabia-Eurasia convergence as previously believed.</p>

scholarly journals Moho depth of the British Isles: a probabilistic perspective

2020 ◽  
Vol 221 (2) ◽  
pp. 1384-1401
Author(s):  
A Licciardi ◽  
R W England ◽  
N Piana Agostinetti ◽  
K Gallagher
Keyword(s):  
Great Britain ◽  
Receiver Function ◽  
Moho Depth ◽  
British Isles ◽  
Data Types ◽  
The North ◽  
Data Driven Approach ◽  
Porcupine Basin ◽  
Reconstructed Surface ◽  
Surrounding Areas

SUMMARY We present a new Moho depth model of the British Isles and surrounding areas from the most up-to-date compilation of Moho depth estimates obtained from refraction, reflection and receiver function data. We use a probabilistic, trans-dimensional and hierarchical approach for the surface reconstruction of Moho topography. This fully data-driven approach allows for adaptive parametrization, assessment of relative importance between different data-types and uncertainties quantification on the reconstructed surface. Our results confirm the first order features of the Moho topography obtained in previous work such as deeper Moho (29–36 km) in continental areas (e.g. Ireland and Great Britain) and shallower Moho (12–22 km) offshore (e.g. in the Atlantic Ocean, west of Ireland). Resolution is improved by including recent available data, especially around the Porcupine Basin, onshore Ireland and Great Britain. NE trending features in Moho topography are highlighted above the Rockall High (about 28 km) and the Rockall Trough (with a NE directed deepening from 12 to about 20 km). A perpendicular SE oriented feature (Moho depth 26–28 km) is located between the Orkney and the Shetland, extending further SW in the North Sea. Onshore, our results highlight the crustal thinning towards the N in Ireland and an E–W oriented transition between deep (34 km) and shallow (about 28 km) Moho in Scotland. Our probabilistic results are compared with previous models showing overall differences around ±2 km, within the posterior uncertainties calculated with our approach. Bigger differences are located where different data are used between models or in less constrained areas where posterior uncertainties are high.

The role of pre-existing weak zones in the formation of the Himalaya and Tibetan plateau: 3-D thermomechanical modelling

2020 ◽  
Vol 221 (3) ◽  
pp. 1971-1983
Author(s):  
Lin Chen ◽  
Lijun Liu ◽  
Fabio A Capitanio ◽  
Taras V Gerya ◽  
Yang Li
Keyword(s):  
Tibetan Plateau ◽  
Early Stage ◽  
Crustal Thickening ◽  
The Tibetan Plateau ◽  
Crustal Material ◽  
Weak Zone ◽  
Orogenic Wedge ◽  
Orogenic Plateau ◽  
Weak Zones

SUMMARY The Tibetan crust is sliced by several east–west trending suture zones. The role of these suture zones in the evolution of the Himalayan range and Tibetan plateau remains unclear. Here we use 3-D thermomechanical simulations to investigate the role of pre-existing weak zones within the Asian Plate in the formation of orogen and plateau growth during continental collision. Our results show that partitioning of deformation along the convergent margin leads to scraping off of crustal material into an orogenic wedge above the margin and crustal thickening in the retro-continent, eventually forming a large orogenic plateau in front of the indenter. Pre-existing weak zone(s) within the retro-continent is reactivated at the early stage of convergence, and facilitates the northward propagation of strain and widening of the orogenic plateau. The northernmost weak zone sets the northern limit of the Tibetan plateau. Our models also show rheological weakening of the congested buoyant crust within the collisional zone drives wedge-type exhumation of deeply buried crust at the southern flank of the plateau, which may explain the formation of the Greater Himalayan Sequence.

Review: Receiver function studies in the southern Canadian Cordillera

1995 ◽  
Vol 32 (10) ◽  
pp. 1514-1519 ◽  
Author(s):  
John F. Cassidy
Keyword(s):  
British Columbia ◽  
Upper Mantle ◽  
Receiver Function ◽  
Vancouver Island ◽  
Moho Depth ◽  
Canadian Cordillera ◽  
Low Velocity ◽  
Strait Of Georgia ◽  
Low Velocity Zone ◽  
Velocity Zone

Receiver function analysis has proven to be a powerful, yet inexpensive tool for estimating the S-wave velocity structure of the crust and upper mantle beneath three-component seismograph stations in the southern Canadian Cordillera. Receiver function studies using a portable broadband seismograph array across southwestern British Columbia provided site-specific estimates for the location of the subducting Juan de Fuca plate. The oceanic crust was imaged at 47−53 km beneath central Vancouver Island, and 60–65 km beneath the Strait of Georgia. Further, these studies revealed a prominent low-velocity zone (VS = −1.0 km/s) that coincides with the E reflectors imaged ~5–10 km above the subducting plate on Lithoprobe reflection lines. The E low-velocity zone was shown to extend into the upper mantle beneath the Strait of Georgia and the British Columbia mainland, to depths of 50–60 km. Combining the receiver function and refraction models revealed a high Poisson's ratio (0.27–0.38) for this feature. The continental Moho was estimated at 36 km beneath the Strait of Georgia, and a crustal low-velocity zone associated with the Lithoprobe C reflectors beneath Vancouver Island was interpreted to extend eastward, near the base of the continental crust, to the British Columbia mainland. Analysis of data from the recently deployed Canadian National Seismograph Network demonstrates the variations in crustal thickness and complexity across the southern Canadian Cordillera, with the Moho depth varying from 35 km in the Coast Mountains, to 33 km near Penticton, to 50 km near the Rocky Mountain deformation front.

scholarly journals Modular specification and verification of closures in Rust

2021 ◽  
Vol 5 (OOPSLA) ◽  
pp. 1-29
Author(s):  
Fabian Wolff ◽  
Aurel Bílý ◽  
Christoph Matheja ◽  
Peter Müller ◽  
Alexander J. Summers
Keyword(s):  
Formal Verification ◽  
Functional Properties ◽  
Type System ◽  
Order Logic ◽  
First Order Logic ◽  
Formal Reasoning ◽  
First Order ◽  
Novel Technique ◽  
Smt Solvers ◽  
Specification And Verification

Closures are a language feature supported by many mainstream languages, combining the ability to package up references to code blocks with the possibility of capturing state from the environment of the closure's declaration. Closures are powerful, but complicate understanding and formal reasoning, especially when closure invocations may mutate objects reachable from the captured state or from closure arguments. This paper presents a novel technique for the modular specification and verification of closure-manipulating code in Rust. Our technique combines Rust's type system guarantees and novel specification features to enable formal verification of rich functional properties. It encodes higher-order concerns into a first-order logic, which enables automation via SMT solvers. Our technique is implemented as an extension of the deductive verifier Prusti, with which we have successfully verified many common idioms of closure usage.

scholarly journals Crustal thickening and endogenic oxidation of magmatic sulfur

2020 ◽  
Vol 6 (31) ◽  
pp. eaba6342
Author(s):  
Ming Tang ◽  
Cin-Ty A. Lee ◽  
Wei-Qiang Ji ◽  
Rui Wang ◽  
Gelu Costin
Keyword(s):  
Oxidation State ◽  
Sulfur Oxidation ◽  
Ore Deposits ◽  
Crustal Thickening ◽  
Sulfate Content ◽  
Southern Tibet ◽  
Ore Deposit ◽  
First Order ◽  
Outstanding Problem ◽  
Relationship Of

Porphyry ore deposits, Earth’s most important resources of copper, molybdenum, and rhenium, are strongly associated with felsic magmas showing signs of high-pressure differentiation and are usually found in places with thickened crust (>45 kilometers). This pattern is well-known, but unexplained, and remains an outstanding problem in our understanding of porphyry ore deposit formation. We approach this problem by investigating the oxidation state of magmatic sulfur, which controls the behavior of ore-forming metals during magma differentiation and magmatic-hydrothermal transition. We use sulfur in apatite to reconstruct the sulfur oxidation state in the Gangdese batholith, southern Tibet. We find that magma sulfate content increased abruptly after India-Eurasia collision. Apatite sulfur content and the calculated magma S6+/ΣS ratio correlate with whole-rock dysprosium/ytterbium ratio, suggesting that residual garnet, favored in thickened crust, exerts a first-order control on sulfur oxidation in magmatic orogens. Our findings link sulfur oxidation to internal petrogenic processes and imply an intrinsic relationship of magma oxidation with synmagmatic crustal thickening.

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