Constraining melt geometries beneath the Afar Depression, Ethiopia from teleseismic receiver functions: the anisotropic H-κ stacking technique

Understanding the nature of the crust has long been a goal for seismologists when imaging the Earth. This is particularly true in volcanic regions where imaging melt storage and migration can have important implications for the size and nature of an eruption. Receiver functions and the H-κ stacking (Hκ) technique are often used to constrain crustal thickness (H) and the ratio of P to S wave velocities (κ). In this paper, I show that it is essential to consider anisotropy when performing Hκ. I show that in a medium with horizontally transverse isotropy a strong variation in κ with back azimuth is present, which characterizes the anisotropic medium. In a vertically transverse isotropic medium, no variation in κ with back azimuth is observed, but κ is increased across all back azimuths. Thus, estimates of κ are more difficult to relate to composition than previously thought. I extend these models to melt-induced anisotropy and show that similar patterns are observed, but with more significant variations and increases in κ. Based on these observations, I develop a new anisotropic H-κ stacking technique which inverts Hκ data for melt fraction, aspect ratio, and orientation of melt inclusions. I apply this to data for the Afar Depression and show that melt is stored in interconnected stacked sills in the lower crust, which likely supply the recent volcanic eruptions and dike intrusions. This new technique can be applied to any anisotropic medium where it can provide constraints on the average crustal anisotropy

Structure of the crust and African slab beneath the central Anatolian plateau from receiver functions: New insights on isostatic compensation and slab dynamics

The central Anatolian plateau in Turkey is a region with a long history of subduction, continental collision, accretion of continental fragments, and slab tearing and/or breakoff and tectonic escape. Central Anatolia is currently characterized as a nascent plateau with widespread Neogene volcanism and predominantly transtensional deformation. To elucidate the present-day crustal and upper mantle structure of this region, teleseismic receiver functions were calculated from 500 seismic events recorded on 92 temporary and permanent broadband seismic stations. Overall, we see a good correlation between crustal thickness and elevation throughout central Anatolia, indicating that the crust may be well compensated throughout the region. We observe the thickest crust beneath the Taurus Mountains (>40 km); it thins rapidly to the south in the Adana Basin and Arabian plate and to the northwest across the Inner Tauride suture beneath the Tuz Gölü Basin and Kırşehir block. Within the Central Anatolian Volcanic Province, we observe several low seismic velocity layers ranging from 15 to 25 km depth that spatially correlate with the Neogene volcanism in the region, and may represent crustal magma reservoirs. Beneath the central Taurus Mountains, we observe a positive amplitude, subhorizontal receiver function arrival below the Anatolian continental Moho at ∼50–80 km that we interpret as the gently dipping Moho of the subducting African lithosphere abruptly ending near the northernmost extent of the central Taurus Mountains. We suggest that the uplift of the central Taurus Mountains (∼2 km since 8 Ma), which are capped by flat-lying carbonates of late Miocene marine units, can be explained by an isostatic uplift during the late Miocene–Pliocene followed by slab breakoff and subsequent rebound coeval with the onset of faster uplift rates during the late Pliocene–early Pleistocene. The Moho signature of the subducting African lithosphere terminates near the southernmost extent of the Central Anatolian Volcanic Province, where geochemical signatures in the Quaternary volcanics indicate that asthenospheric material is rising to shallow mantle depths

Crustal structure beneath the Indochina peninsula from teleseismic receiver functions

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95076/1/grl27455.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/95076/2/grl27455-sup-0012-ts01.pd

An innovative tailored instructional design for computer programming courses in engineering

Industry 4.0 and 5.0 topics are emerging fields and have seen rising demand recently. There is a critical need, on the other hand, for improved methods of instructing programming languages since a growing lack of student motivation during the pandemic has had a deleterious influence on the education of programmers. In this context, online/hybrid computer programming courses must be addressed with innovative solutions to support the field with well-educated professionals. In this paper, we present a case study to propose an innovative tailored instructional design for the online/hybrid learning environments for programming courses in engineering faculties. To develop the instructional design, the Kemp Instructional Design Model was followed. The instructional design is a result of the main outputs of the RECOM “Redesigning Introductory Computer Programming Using Innovative Online Modules” project, which aims to bridge the gap between the existing course design in programming courses and the needs of "Covid” and “post-Covid” generation students

Modeling the adsorption of benzeneacetic acid on CaO2 nanoparticles using artificial neural network

AbstractThe present work reported a method for removal of benzeneacetic acid from water solution using CaO2 nanoparticle as adsorbent and modeling the adsorption process using artificial neural network (ANN). CaO2 nanoparticles were synthesized by a chemical precipitation technique. The characterization and confirmation of nanoparticles have been done by using different techniques such as X-ray powder diffraction (XRD), high resolution field emission scanning electron microscope (HR-FESEM),transmittance electron microscopy (TEM) and high-resolution TEM (HRTEM) analysis. ANN model was developed by using elite-ANN software. The network was trained using experimental data at optimum temperature and time with different CaO2 nanoparticle dosage (0.002–0.05 g) and initial benzeneacetic acid concentration (0.03–0.099 mol/L). Root mean square error (RMS) of 3.432, average percentage error (APE) of 5.813 and coefficient of determination (R2) of 0.989 were found for prediction and modeling of benzeneacetic acid removal. The trained artificial neural network is employed to predict the output of the given set of input parameters. The single-stage batch adsorber design of the adsorption of benzeneacetic acid onto CaO2 nanoparticles has been studied with well fitted Langmuir isotherm equation which is homogeneous and has monolayer sorption capacity

Geochemistry of free and dissolved gases in the Amik basin area (Turkey) and its relationships with the tectonic setting

Twenty-two gas samples were collected in August 2012 in the area of Amik basin (Turkey). Two samples were collected from gas seeps, one was a bubbling gas in a thermal spring, while the remaining were dissolved gases from cold and thermal groundwaters (T 16-43 °C). All gases were analysed for their chemical composition (He, H2, O2, N2, CH4 and CO2) and for their He isotopic composition. Dissolved gases were also analysed for the carbon isotopic composition of the total dissolved carbon (TDC), while free gases also for their higher hydrocarbon (C1 – C5) content and for D of H2 and CH4, 13C of CH4 Basing on their chemical composition, the gases can be roughly subdivided in three groups. Most of the dissolved gases (16) belonging to the first group were collected from springs or shallow wells (< 150 m depth). All these samples contain mainly atmospheric gasses with very limited H2 (< 80 ppm) and CH4 (1 – 2700 ppm) contents and minor concentrations of CO2 (0.5 – 11.2 %). The isotopic composition of TDC evidences an almost organic contribution. The only exception is represented by the CO2-richest sample where a small but significant mantle contribution is found. Such contribution can also be evidenced in its 3He rich isotopic composition. Further three samples of this group evidence a small mantle contribution. These samples were collected in the northern part of the basin along the main tectonic structures delimiting the basin and close to areas with quaternary volcanic activity. A second group is composed by two dissolved gases collected from deep boreholes (> 1200 m depth). Their composition is typical of hydrocarbon reservoirs being very rich in CH4 (> 78 %) and N2 (> 13%). Also the water composition is typical of saline connate waters (Cl- and B-rich, SO4-poor). C-isotopic composition of methane ( 13C -65% ) points to a biogenic origin while He-isotopic composition indicates a prevailing crustal signature for one (R/Ra 0.16) of the sites and small mantle contribution for the other (R/Ra 0.98). To the last group belong four gas samples taken at two sites within the ophiolitic basement that crops out west of the basin. These gases have the characteristic composition of gas generated by low temperature serpentinisation processes with high hydrogen (37 – 50 %) and methane (10 – 61 %) concentrations. While all gases show an almost identical D-H2 of -750h those of one of the two sites display an isotopic composition of methane ( 13C -5h D -105% ) and a C1/[C2+C3] ( 100) ratio typical of abiogenic hydrocarbons and mantle-type helium (R/Ra: 1.33), while those of the other site evidence a contribution of a crustal (thermogenic) component ( 13C-CH4 -30h D -325h C1/[C2+C3] 3000). Such crustal contribution is also supported by higher N2 contents (40% instead of 2%) and lower He-isotopic composition (R/Ra 0.07). The preliminary results highlight contributions of mantle-derived volatiles to the fluids vented along the Amik Basin. The main tectonic structure of the area, the Death Sea Fault, and other parallel structures crossing the basin seem to be the responsible for deep-originated volatiles drainage towards shallow levels