Annals of Geophysics最新文献

{"title":"A refined catalogue of focal mechanisms for the Intra‑Carpathian region of Romania: implications for the stress field and seismogenic features assessment","authors":"E. Oros, M. Popa, D. Paulescu, A. Plăcintă, C. Ghita","doi":"10.4401/ag-8387","DOIUrl":"https://doi.org/10.4401/ag-8387","url":null,"abstract":"We present a refined and the most complete catalogue of the focal mechanisms for the Intra-Carpathian region of Romania. It contains the high-quality solutions computed for 1217 earthquakes recorded between 1909 and 2018. Primary data gathered from the original seismograms and seismic bulletins have been used to compute the source parameters and focal mechanisms solutions. The focal mechanisms have been obtained using the HASH method by the polarities and S/P amplitudes ratios inversion. Our catalogue provides data necessary for the investigation of the contemporary stress field at different scales with high spatial and temporal resolution. We determined the stress field characteristics through formal inversion of focal mechanisms and also computed the reactivation potential of the active fault systems using the Win‑Tensor program. The stress field is heterogeneous, with SHmax significantly deviating from the first-order stress field direction and also with strong local variations in the stress regime.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88203781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The FastVRP automatic platform for the thermal monitoring of volcanic activity using VIIRS and SLSTR sensors: FastFRP to monitor volcanic radiative power","authors":"F. Torrisi, E. Amato, C. Corradino, C. Del Negro","doi":"10.4401/ag-8823","DOIUrl":"https://doi.org/10.4401/ag-8823","url":null,"abstract":"Satellite thermal remote sensing is widely used to detect and quantify the high-temperature vol- canic features produced during an eruption, e.g. released radiative power. Some space agencies provide Fire Radiative Power (FRP) Products to characterize any thermal anomaly around the world. In particular, Level-2 FRP Products of the Visible Infrared Imaging Radiometer Suite (VIIRS) and the Sea and Land Surface Temperature Radiometer (SLSTR) are freely available online and they allow to monitor high-temperature volcanic features related to the dynamics of volcanic activity. Here, we propose the FastVRP platform developed in Google Colab to process automatically the FRP Products provided by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) space agencies. FastVRP was designed to monitor the volcanic radiative power (VRP) related to eruptive activity of Mt. Etna (Sicily, Italy). We compared the quality of these FRP Products during a number of recent paroxysmal lava fountains occurred at Etna volcano between February and March 2021. We highlighted the advantages and the limits of each sensor in monitor- ing intense volcanic eruptions lasting a few hours. Furthermore, we combine the mid-high spatial/ low temporal resolution VIIRS and SLSTR with the low spatial-high temporal resolution SEVIRI (Spinning Enhanced Visible and Infrared Radiometer Imager) to improve estimates of the energies released from each paroxysmal episode. In particular, we propose a fitting approach to enhance the accuracy of SEVIRI low spatial-high temporal resolution measurements exploiting the few acqui- sitions from VIIRS and SLSTR high spatial-low temporal resolution during lava fountain cooling phase. We validated the radiative power values forecasted from VIIRS and SLSTR with the radiative power values retrieved using MODIS (Moderate Resolution Imaging Spectroradiometer) sensor.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84195220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Upper Mantle Anisotropy beneath Northern Algeria from Shear-Wave Splitting: Anisotropy beneath Northern Algeria","authors":"Zohir Radi, Abdelkarim Yelles Chaouche, S. Guettouche, G. Bokelmann","doi":"10.4401/ag-8839","DOIUrl":"https://doi.org/10.4401/ag-8839","url":null,"abstract":"Northern Algeria is a large region in the north-western of Africa, lying on the collision boundary between the African and Eurasian plates. Few studies on Lithosphere and Mantle deformation have been conducted in this region. To better understand the seismic anisotropy patterns beneath this area, we used data from 17 broadband stations installed in Tellian and the Saharan atlases using the SKS shear wave splitting method by processing hundreds of teleseismic events. To estimate the seismic anisotropy, two parameters were calculated, the fast polarization direction and the delay time for each station-event pair. The results show that the seismic anisotropy can be described by two main orientations, ENE-WSW follows the general trend of the Saharan Atlas, particularly in the central and western parts, and ESE-WNW follows the Hodna Mountains in south-eastern Algeria. Our results show that the anisotropy can be explained by single and heterogeneity in the anisotropic structure, where the measurements are very scattered, and the delay time and fast direction changed with the events backazimuth. In the ABSD, CBBR and CDCN stations, which lie in the arc between the Sahara Atlas and the Aurès Mountains, the origin hypothesis of the seismic anisotropy can be linked to the existence of a detached slab. Moreover, in ABZH, OKGL and EARB stations located in the Kabylide and Western regions, it can be associated with the Gibraltar slab. Both slabs sinking in the African margin mantle were previously imaged by seismic tomography. For the remaining stations, the single-layer best explains the observed seismic anisotropy from their regular fast polarization direction. The comparison of the obtained fast directions with GPS measurements shows that anisotropy fast axes are nearly perpendicular to the convergence direction between the African and Eurasia plates.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73994312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the possibility of rogue wave generation based on the dynamics of modified Burridge-Knopoff model of earthquake fault","authors":"N. O. Nfor, Ndikum Eric Ndoh, Marceline Motchongom Tingue, Vivian Ndfutu Nfor","doi":"10.4401/ag-8856","DOIUrl":"https://doi.org/10.4401/ag-8856","url":null,"abstract":"In this study we propose a modified Burridge‐Knopoff model of earthquake fault, in which two tectonic plates are strongly coupled by nonlinear springs. By minimizing the effects of the veloci‐ ty‐weakening stick‐slip friction force between the masses and the moving surface, and in the limit of low amplitude oscillations; the system exhibits both stick‐slip and damped oscillatory motions as the values of some parameters are varied. Such motions usually characterize the dynamics of an earthquake fault, even though it is not always felt because of the low amplitude of vibrations. However when enough stress builds up in the subduction zones to overcome the frictional forces between tectonic plates, the oceanic rocks suddenly slip and there is violent release of energy at the epicentre. This outburst of energy simply signifies the generation of a very large amplitude and localized nonlinear wave. Such wave profile exactly fits the Peregrine solution of the damped/ forced nonlinear Schrodinger amplitude equation, derived from the modified one‐dimensional Burridge‐Knopoff equation of motion. In the regime of minimal or no frictional forces, these mon‐ ster waves suddenly appear and disappear without traces as shown by the numerical investigations. Our results strongly suggest that rogue waves emanates from the dynamics of nonlinearly coupled tectonic plates in subduction zones. This is further complemented by the fact that these giant waves were initially observed in Pacific and Atlantic oceans, which play hosts to the world’s largest oceanic subduction zones.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86208156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Two-layer model of anisotropy beneath Myanmar and Thailand revealed by shear-wave splitting","authors":"Kasemsak Saetang","doi":"10.4401/ag-8769","DOIUrl":"https://doi.org/10.4401/ag-8769","url":null,"abstract":"The first model of two layers is presented to study the anisotropy pattern beneath Myanmar and Thailand using shear-wave splitting. Teleseismic activity recorded by 15 permanent broadband stations was analysed to investigate the anisotropy and to understand the flow direction in the mantle. The flow direction and speed were observed in the forms of fast polarisation direction (𝜙) and delay time (𝛿𝑡) between fast and slow components. The measurements showed that a two-layer model beneath stations better explicates the splitting observations than a single-layer model. The upper and lower layers were interpreted as lithosphere and asthenosphere in similar patterns and compared with GPS (Global Positioning System) velocity fields and strain rate fields. Two groups of 𝜙 can be classified and matched with West-Burma Terrane (WBT) and Shan-Thai Terrane (STT). The 𝜙 represents that West-Burma Terrane moves in a northward direction, Shan-Thai Terrane and Indo-China Terrane (ICT) move in a south-eastern direction, and West-Burma Terrane has less anisotropy of 𝜙 than Shan-Thai Terrane.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2022-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78789127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The assessment of earthquake hazard in Italy: a review","authors":"D. Slejko, G. Valensise, C. Meletti, M. Stucchi","doi":"10.4401/ag-8863","DOIUrl":"https://doi.org/10.4401/ag-8863","url":null,"abstract":"We present a review of the assessment of earthquake hazard in Italy, with special reference to the relationships between hazard models and building codes. After early attempts at hazard assessment in the 19th century, the 28 December 1908, Messina Straits earthquake prompted the inception of the first national seismic legislation, passed in early 1909. Nevertheless, the official building code started to be based on a truly scientific background only after 1980, when the catastrophic Irpinia (southern Italy) earthquake forced the qualified authority to accept a science-based assessment (statistics on the earthquake catalogue data) to support the implementation of the new national seismic zonation. Later on, between 1985 and 2000, the two basic components of seismic hazard assessment, namely the earthquake record and the distribution of earthquake sources, were greatly developed through investigations carried out by the Gruppo Nazionale Difesa dai Terremoti and by the Istituto Nazionale di Geofisica. Along with the improvement of basic data, the Italian seismological community started developing a new hazard model (PS4), based on the concept of seismotectonic probabilism, aimed at supplying the Italian Government with a solid reference frame for updating the seismic zonation and building code. Nevertheless, this goal was achieved only two decades later: on 31 October 2002 a moderate-size earthquake caused the death of 27 children and a teacher in a collapsed school of southern Italy, forcing the qualified authority to take a major step of modernization for the second time in 22 years. The entire Italian territory, including areas of rare and sparse seismicity, was subdivided into four seismic zones, mainly on the basis of PS4 results. In 2004, the Italian seismological community developed MPS04, a fully updated hazard model that was initially conceived only in view of updating the seismic zonation. In 2007, MPS04 was extended to provide design spectra for a new building code, which was finally adopted in 2009, following the disastrous L’Aquila (central Italy) earthquake. The experience of the European project for seismic hazard assessment named SHARE, completed in 2013, represented a step forward and put the basis for a new project, termed MPS19, designed specifically to provide a sound basis for updating the  Italian building code.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2022-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84892146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring the Kinematic Structure of Mount Etna Volcano (Sicily, Italy) by Deformation Analysis and Gravity Gradient Tensors","authors":"Ayça Çırmık, F. Doğru, Oya Ankaya Pamukçu, Başak Turguz, A. Bonforte","doi":"10.4401/ag-8719","DOIUrl":"https://doi.org/10.4401/ag-8719","url":null,"abstract":"Ground deformation monitoring of active volcanoes is used routinely to determine phases of vol‐ cano unrest and can provide insights in the evolving plumbing system of a volcano and the influence local tectonics structures have on the volcano tectonic evolution of the volcanic edifice. Volcanic deformation analysis can be performed using velocity and direction measurements of the ground surface using Global Navigation Satellite System (GNSS). In this study, we perform two‐dimen‐ sional deformation analyses of pre‐ and post‐eruptive phases with the scope of determining the strain before and after an eruptive phase at Mt. Etna Volcano (southern Italy) during 2004‐2006. In order to do so, we analyse the GNSS displacement data from Mt. Etna between 2004‐2005 and 2005‐2006 using the dedicated SSPX software. The extention, dilation and rotation maps of the study area were determined. The contraction and volumetric decrease concomitant the 2004‐2005 effusive eruptive period and extension and volumetric increase for the 2005‐2006 data series were observed. The deformation on the northeast part of Mt. Etna Volcano, which showed different characteristics with respect to its surroundings, was thought to be conditioned by the dynamic of the Pernicana fault system. Additionally, Complete Spherical Bouguer (CSB) gravity anomaly and the gravity gradient tensors were calculated giving insight on the subsurface structures of Mt. Etna Volcano and its surroundings.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76480852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revitalizing vintage seismic reflection profiles by converting into SEG-Y format: case studies from publicly available data on the Italian territory","authors":"M. Buttinelli, F. Maesano, D. Sopher, Fabio Feriozzi, S. Maraio, F. Mazzarini, L. Improta, R. Vallone, F. Villani, R. Basili","doi":"10.4401/ag-8883","DOIUrl":"https://doi.org/10.4401/ag-8883","url":null,"abstract":"In recent decades, geological modeling has significantly evolved, relying on the growing potential of hardware and software to manage and integrate vast datasets of 2D-3D geophysical underground data. Therefore, digitization and integration with other forms of data can often improve understanding of geological systems, even when using so-called vintage or historical data. Seismic reflection data have been extensively acquired mainly for hydrocarbon exploration since the 60s generating large volumes of data. Typically, these data have been for private commercial use and are relatively unavailable for research. However, with time, large volumes of vintage seismic reflection data in many countries worldwide are now becoming publicly available through time-based de-classification schemes. Such data have a great potential for modern-day geo-research, unleashing opportunities to improve geological understanding through re-interpretation with modern methods. However, a downside of these vintage data is that they are often only available in analog (paper, raster) format. The vectorization of these data then constitutes an essential step for unlocking their research potential. In 2018 INGV established the SISMOLAB-3D infrastructure, which is mainly devoted to analyzing digital subsurface data, such as seismic reflection profiles and well-logs, to build 2D-3D geological models, principally for seismotectonics, seismic hazard assessment, and geo-resources applications. In this contribution, we discuss the robustness of the WIGGLE2SEGY code, firstly published by Sopher in 2018, focusing on examples from different tectonic and geodynamic contexts within Italian territory. We applied the SEG-Y conversion method to onshore and offshore raster seismic profiles related to ceased exploration permits, comparing the results with other published archives of SEG-Y data obtained from the conversion of vintage data. Such an approach results in digital SEG-Y files with unprecedented quality and detail. The system- atic application of this method will allow the construction of a comprehensive dataset of digital SEG-Y seismic profiles across Italy, thereby expanding and sharing the INGV SISMOLAB-3D port- folio with the scientific community to foster innovative and advanced scientific analysis.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75099359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatio-temporal analysis of b-value prior to 28 April 2021 Assam Earthquake and implications thereof","authors":"V. Sarma, Dipok K. Bora, Rajib Biswas","doi":"10.4401/ag-8802","DOIUrl":"https://doi.org/10.4401/ag-8802","url":null,"abstract":"Here, we report a Spatio-temporal analysis of the frequency magnitude distribution of earthquakes (b-value) before the 28th April 2021 (Mw 6.4) earthquake event observed in northeast India. To esti- mate the average b-value for the study region, a data set of 750 earthquake events with magnitude Mw ≥ 3.9 is extracted from the homogenous part of the earthquake catalog (1950-2021) documented by the United States Geological Survey (USGS) and International seismological center (ISC) in the region. For spatial analysis of the disparities in b-value, the whole study region is subdivided into 16 square grids of dimension 1o×1o and the b-value is calculated for each subsection. In congruence with other studies, this work yields b-values ranging from 0.66 to 1.25. After the calculation of the b-value for each grid, it is observed that the grid with the epicentral location of the 28th April 2021 (6.4) earthquake has a low b-value. Accordingly, the spatial correlation and aberrant pattern between b-value and focal depth have been comprehensively explored. It is observed that the b-value sig- nificantly dips within a depth range of ~15-35 km which implicates high-stress accumulation and crustal homogeneity. The depth-wise variation in b-value infers the antithetical relationship between b-value and crustal stress. Mostly interplate earthquakes are observed in the study region; thereby hinting at intense seismicity at the upper crust.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76960946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"WWLLN Data Used to Model the Global Ionospheric Electric Field Generated by Thunderstorms","authors":"V. Denisenko, M. Rycroft","doi":"10.4401/ag-8821","DOIUrl":"https://doi.org/10.4401/ag-8821","url":null,"abstract":"Electric currents flowing in the atmospheric global electric circuit (GEC) are closed by ionospheric currents. The physical and mathematical approach to simulate the ionospheric potential which drives these currents has been described in our previous papers. Only the internal electric fields and currents generated by thunderstorms are studied, and without any magnetospheric current sources or generators. The atmospheric conductivity profiles with altitude are empirically determined, and the topography of the Earth’s surface is taken into account. A two-dimensional approximation of the ionospheric conductor is based on the high conductivity along the geomagnetic field; the Pedersen and Hall conductivities are calculated using empirical models. The potentials in the E- and F-layers of the ionosphere are considered to be constant along each magnetic field line. The main progress in comparison with previous versions of the model is obtained through applying the global distribution of thunderstorms obtained from the ground-based World Wide Lightning Location Network. Under typical conditions for July, under low solar activity in 2008, at 18:00 UTC, the calculated maximum potential difference in the ionosphere is 54 V. This newest version of our model contains the equatorial electrojets. There are day-time electrojets, the strengths of which are up to 65 A, and night-time ones (of up to 40 A), while the total current flowing in the GEC is taken to be equal to 1.43 kA in our model to satisfy the Carnegie curve, i.e. the diurnal variation of the vertical electric field at ground level with UTC. The maximum of the electric potential is shifted from Africa to South-East Asia in the new model. The equatorial electrojets also change their position, direction and intensity.","PeriodicalId":50766,"journal":{"name":"Annals of Geophysics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82820630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}