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Mapping hydrothermal alteration at the Fentale-Dofan magmatic segment of the Main Ethiopian Rift
Full text linkThe Main Ethiopian Rift (MER) is characterized by extensional tectonics and volcanism, associated with active hydrothermal systems, hydrothermal alteration and fumarolic deposits. The spatial distribution of these hydrothermal products and their link with faults and rock types provides important clues to what controls fluid flow in the subsurface. However, little is known about this in the East African Rift. We address this issue with a multidisciplinary approach in the Fentale-Dofan magmatic segment of the MER, an area characterized by intense volcanic and tectonic activity and a geothermal prospect. Primarily we conduct mapping of hydrothermal alteration and fumarolic deposits, and rock lithologies using a surface feature classification technique of multispectral satellite images. Then we interpret the map using a new database of faults and active hydrothermal manifestations such as hot-springs and fumaroles. We find that the surface hydrothermal alteration and deposits are mainly focused near Fentale and the Dofan Volcanic Complex (DVC). At DVC the hydrothermal products are focused on rhyolites on the western side of the volcano, in an area of intense NNE striking, rift parallel faults. At Fentale volcano the hydrothermal products are mainly associated with ignimbrite and show a circular pattern around the volcanic edifice, but also in places follow the NNE striking faults. At Fentale, the more complex association of hydrothermal products and active manifestations around the edge of the ignimbrite suggests formation contacts may also localize fluid flow in places. At both volcanoes the association between hydrothermal products with either the rhyolites and ignimbrites is likely due to them being relatively easily altered (in comparison to basalt), and also their brittle nature allows for fracturing through which localized fluid flow can occur (as opposed to the sediments). The general pattern of hydrothermal products suggests a stronger structural influence at the DVC with respect to Fentale. The presence of hydrothermal products and active hydrothermal manifestations, along with other lines of evidence such as locus of subsurface dike intrusion at the volcanic centres, suggest that discrete and localized magma reservoirs beneath Fentale and the DVC are the heat source for hydrothermal circulation. Our study also demonstrates that geology, including hydrothermal deposits, can be successfully mapped using automated remote sensing based classification
Seismicity induced by fluid migration in the Main Ethiopian Rift
No full textIn the last years a large amount of geological, geophysical and seismological data have been produced by induced seismicity studies. These studies have given a great contribute to the understanding of the physical processes triggered by the fluid-structure interaction in active fault zones. Frictional laboratory experiments on fault rock samples have shown that the style of deformation (e.g. stick-slip or aseismic creeping) can change in presence of fluids. In addition, high-precision seismicity locations coupled with the interpretation of high-resolution seismic profiles have allowed to understand the time-spatial evolution of the permeability inside complex fault systems. Here we integrate different data available from the literature to model the stress perturbations induced by wastewater injection in the Val d’Agri oil field by coupled fluid flow and geomechanical numerical simulations. We model the behaviour of main faults involved in the induced seismicity process by frictional contacts in a finite element framework. The permeability into the fault zones are changed in order to understand the role of these structures either as fluid pathways or as efficient compartmentalization barriers for the pore pressure diffusion front associated to wastewater injection. To do this a fault zone model that considers the spatial variation of the hydromechanical properties from the damage zone to the fault core has been implemented in the numerical code. Final aim is to have a more complete picture of the induced seismicity in Val d’Agri oilfield as a consequence of the pore pressure increase as well as its relationship with the deformation style of the fault system and the active stress field
Evidence of Fluid Induced Earthquake Swarms From High Resolution Earthquake Relocation in the Main Ethiopian Rift
No full textFluid overpressure and fluid migration are known to be able to trigger or induce fault slip. However, relatively little is known about the role of fluids on generating earthquakes in some of the major continental rifts. To address this, we investigate the interaction between fluids and faults in the Main Ethiopian Rift (MER) using a large seismicity catalog that covers both the rift axis and rift margin. We performed cross-correlation analysis on four major earthquake clusters (three within the rift and one on the rift margin) in order to significantly improve accuracy of the earthquake relative relocations and to quantify families of earthquakes in which waveforms are similar. We also analyzed variation of seismicity rate and seismic moment release through time for the four clusters. The major results are that for all four clusters the earthquake relocations are 5–15 km deep, aligned to clear N-NNE striking, steeply (>60°) dipping planes. For the three clusters within the rift, the cross-correlation analysis identifies earthquake families that occur in short swarms during which seismic rate and moment release increases. Together, this space and time pattern of the seismicity strongly points toward them being fluid induced, with fluid likely sourced from depth such as mantle derived CO2. In contrast, the seismicity on the rift margin lacks earthquake families, with occurrence of earthquakes more continuous in nature, which we interpret as pointing toward tectonic stress-driven microseismic creep. Overall, our results suggest that deep sourced fluid migration within the rift is an important driver of earthquake activity.
Key Points
Cross correlation and high-resolution relocation are used to investigate driving mechanisms of seismicity during continental rifting
Earthquake relocation aligns seismicity to N−NNE striking, ∼60° dipping planes corresponding to rift normal faults
The cross-correlation analysis identifies similar earthquakes that occur in swarms in the rift, pointing toward them being fluid induced
Plain Language Summary
Fluids such as water and carbon dioxide that come from the deep Earth can move toward the surface by following fractures and faults. When this happens, these fluids make it easier for the faults to move, causing lots of small earthquakes to happen in short periods of time and in the same place. These earthquake swarms have typical characteristics such as waveforms that are incredibly similar to each other. In our study, we are interested in understanding how important the movement of fluids is for the generation of earthquakes during the breakup of continents. We investigated the presence of these characteristics for earthquakes in the Main Ethiopian Rift in East Africa. Major findings are that earthquake swarms within the rift have characteristics that indicate earthquakes are generated by fluid flow along faults. In contrast at the edges of the rift, the earthquakes are different in character, which indicates that they are caused by tectonic motion of the plates rather than fluid migration
Extensional earthquakes in the absence of magma in northern Afar: insights from InSAR
No full textIn magma-rich rifts, normal faulting is commonly thought to be induced by dike intrusions. However, whether fault slip occurs purely tectonically is unclear. An earthquake sequence starting with a Mw 5.5 earthquake occurred in December 2022 in northern Afar, a continental rift near breakup. InSAR measurements show that seismicity was caused by normal faulting alone, without involvement of magma movements. Our best-fit InSAR models show that conjugate faults ruptured during the seismic sequence with mainly normal dip-slip and total deformation corresponding to a Mw 5.7 event, in agreement with local seismic recordings. Our models show that tectonic faulting accommodates 26 cm of extension corresponding to ∼30 years of plate spreading without any link to magma. Our observations point toward significant along-rift variation in the proportion of extension from faulting, potentially caused by along-rift variations in rate of extension and/or from a spatially and temporally segmented supply of magma
Cholinergic Urticaria, an Effective and Safe “Off Label” Use of Dupilumab: A Case Report with Literature Review
Full text linkCholinergic Urticaria (CholU) is a form of generalized urticaria induced by an increase in core body temperature that activates the sweat reflex. Clinically it is characterized by localized and highly itchy wheals with surrounding erythema and can occur in response to exercise, hot baths and/or emotional stress. Dupilumab is a fully human monoclonal antibody specifically designed to simultaneously inhibit the activity of interleukin-4 (IL-4) and interleukin-13 (IL-13), which play a key role in the inflammation cascade of type 2. We report the case of a 26-year-old man suffering from CholU for 3 years, unresponsive to standard treatment in which off-label therapy was undertaken with Dupilumab, 600 mg subcutaneous as a loading dose and then 300 mg every 15 days. The daily Visual Analogue Scale (VAS) score was used to assess the efficacy of the therapy. Already after the first two administrations, the patient no longer had CholU episodes and resumed regular sporting activity, with a marked improvement in the quality of life. A possible mechanism of Dupilumab in reducing the manifestations of CholU is the blocking of the IL-4 pathway and the expression of the high-affinity IgE receptor (FcεR1) on B cells, mast cells (MCs) and basophils. By decreasing the production of FcεR1, the adhesion of IgE to the surface of MCs decreases with consequent reduction of MCs activation and histamine release. Further experience and large-scale studies may be needed to establish whether Dupilumab can be a therapeutic alternative in CholU, especially in patients who do not respond to standard treatment
Henoch-Schönlein Purpura Following the First Dose of COVID-19 Viral Vector Vaccine: A Case Report
Full text linkA 76 year-old female came to our observation one week after the vaccination with ChAdOx1 nCoV-19 AZD1222 for the onset of purpuric rash on her gluteal and legs regions associated with coxalgia and episodes of macrohaematuria. Henoch-Schönlein purpura (HSP) was diagnosed on the basis of the revised criteria developed by the European League Against Rheumatism, the Paediatric Rheumatology International Trials Organization, and the Paediatric Rheumatology European Society (EULAR/PRINTO/PRES). HSP is a common IgA-mediated small vessel vasculitis, typical of childhood, that affects several systems and is characterized by a tetrad of dermatological, abdominal, joint, and renal manifestations. The Etiology of HSP is not completely understood, but it was observed following upper respiratory tract infections, medications, vaccinations, and malignancies. HSP has previously been reported following immunization with various vaccines, mostly within 12 weeks post, suggesting a possible correlation. To our knowledge, this is the first report of the possible association between COVID-19 ChAdOx1 nCoV-19 AZD1222 and the onset of HSP in a previously healthy woman. No similar cases were reported amongst 23.848 participants in the ChAdOx1 nCoV-19 AZD1222 trial
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Interaction between active faults and migration of fluids
No full textThe aim of the research project is to investigate the influence that fluids and their migration can have on the seismicity of active faults.
The study area is the Fentale-Dofan magmatic segment of the Main Ethiopian Rift (MER). It is an area of active rifting processes with widespread seismicity and hydrothermal manifestations. The seismic database used here was collected during the EAGLE project from October 2001 to February 2003.
Initially, the events were relocated with a linear location method using Hypoinverse software and a simple 1D velocity model. This allows me to understand the overall distribution of seismicity. Then, a non-linear location method was performed, using NonLinLoc software with an 2D velocity model of the area. This produced an earthquake distribution more grouped that shows a pattern parallel to the rift.
Then, the cross correlation analysis was performed. It reveals the presence of families of similar earthquakes in the clusters into the rift but not on the border fault. The occurrence of these families corresponds to an increase in the seismic rate. The differential times for the events with high cross correlation coefficients were used to improve the earthquake location using the HypoDD software. While the earthquakes in the rift are characterized by the presence of swarms, locally high b-value, small release of seismic moment, alignment of events along high angle normal faults, a similar pattern is absent or not as clear in the earthquakes on the border fault. In conclusion, it is possible to assume that the earthquakes in the rift show clear characteristics attributable to the fluid-fault interaction process. Instead, these characteristics are less clear on the western border faults, where it is more likely a tectonic dominated process.
In the end, a map of hydrothermal deposits was. No clear correlation between the seismicity and the hydrothermal deposits is observed. Then I can conclude that the fluid induced earthquakes in the rift are caused by a different fluid circulation compared to the one that generates the hydrothermal deposits
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