bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple parameters anomalies for verifying the geosystem spheres coupling effect: a case study of the 2010 Ms7.1 Yushu earthquake in China
Authors: Shuo Zheng  , Lixin X. Wu  , Kai Qin
Published: June 2021

In the research of earthquake anomaly recognition, the coupling effect of multiple geosystem spheres can be expected to reasonably interpretating the correlation between various anomalous signals before strong earthquake. Specially, the development of the Lithosphere–Atmosphere–Ionosphere (LAI) coupling model has been accepted as verified by some experimental, thermal and electromagnetic data. However, quasi-synchronous anomalies of the multiple parameters, including thermal, radon and electromagnetic data, have not been reported in a single event case for verifying the geosystem spheres coupling effect. In this paper, we firstly summarized the reported studies on the power spectrum density (PSD) in the ELF/VLF band and radon data recorded from Guza seismic station. Then, historical surface latent heat flux (SLHF) data from the NCEP/NCAR Reanalysis Project was employed for investigating anomalous change in a month before the April 14, 2010, Ms7.1 Yushu earthquake which is one of the typical intra-continental earthquakes in Tibet Plateau. The results from spatial and temporal analysis revealed that anomalous fields of PSD and SLHF data were located close to the epicenter and the ends of some active faults at Bayan Har Block and all anomalous dates converged between April 8 and 11 (6 to 3 days before the Yushu earthquake). Therefore, we suggest that the anomalies of multiple parameters before the main shock are related with the Yushu earthquake. This paper could give an ideal case study to verify the geosystem spheres coupling effect happened in a single event.
ANNALS OF GEOPHYSICS: AD MAJORA
Authors: Fabio Florindo  , Francesca Bianco  , Paola De Michelis  , Simona Masina  , Giovanni Muscari  , Francesco Caprara  , Anna Grazia Chiodetti  , Edoardo Del Pezzo  , Stefano Gresta
Published: June 2021

Annals of Geophysics is a bimonthly international journal, which publishes scientific papers in the field of geophysics sensu lato. It derives from Annali di Geofisica, which commenced publication in January 1948 as a quarterly periodical devoted to general geophysics, seismology, earth magnetism, and atmospheric studies. The journal was published regularly for a quarter of a century until 1982 when it merged with the French journal Annales de Géophysique to become Annales Geophysicae under the aegis of the European Geophysical Society. In 1981, this journal ceased publication of the section on solid earth geophysics, ending the legacy of Annali di Geofisica. In 1993, the Istituto Nazionale di Geofisica (ING), founder of the journal, decided to resume publication of its own journal under the same name, Annali di Geofisica. To ensure continuity, the first volume of the new series was assigned the volume number XXXVI (following the last issue published in 1982). In 2002, with volume XLV, the name of the journal was translated into English to become Annals of Geophysics and in consequence the journal impact factor counter was restarted. Starting in 2010, in order to improve its status and better serve the science community, Annals of Geophysics has instituted a number of editorial changes including full electronic open access, freely accessible online, the possibility to comment on and discuss papers online, and a board of editors representing Asia and the Americas as well as Europe. [...]
The Atmospheric Composition Validation and Evolution Workshop (ACVE2013) - Recommendations
Authors: Stefano Casadio  , Angelika Dehn  , Thorsten Fehr  , Bojan R. Bojkov
Published: June 2021

During the last 18 years, the European Space Agency (ESA) has provided the scientific community with a large amount of valuable atmospheric composition data produced by a series of instruments, starting with GOME [Burrows et al., 1999], on-board the ERS-2 satellite (1995-2011), and followed by the GOMOS [Kyrola et al., 2004], MIPAS [Fischer et al., 2008], and the SCIAMACHY [Bovensmann et al., 1999], all flying on-board the Envisat satellite (2002-2012). These observations will be continued by the Sentinel-5 Precursor, Sentinel-4 and Sentinel-5 and extended the EarthCARE and ADM missions for aerosols and clouds. […]
Analysis of the spatial distribution between successive earthquakes in aftershocks series
Authors: Elisaveta Georgieva Marekova
Published: June 2021

The earthquake spatial distribution is being studied, using catalogs for different recent aftershock series. The quality of the available data, taking into account the completeness of the magnitude, is examined. Based on the analysis of the catalogs, it was determined that the probability densities of the inter-event distance distribution collapse into a single curve when the data were rescaled. The collapse of the data provides a clear illustration of aftershock-occurrence self-similarity in space.
Eruption patterns of parasitic volcanoes
Authors: Izumi Yokoyama
Published: June 2021

Eruption patterns of parasitic volcanoes are discussed in order to study their correlation to the activities of their parental polygenetic volcanoes. The distribution density of parasitic vents on polygenetic volcanoes is diversified, probably corresponding to the age and structure of parental volcanoes. Describing existing parasitic cones contextually in relation to parental volcanoes is as indispensable as collecting observational data of their actual formations. In the present paper, spatial distributions of parasitic cones are classified tentatively into the following three categories: individually radial, directionally radial and annular determined according to feature’s placement around the central axes of the parental volcanoes. The formations of parasitic vents are discussed from the standpoint of material mechanics. Derived from this approach, the maximum shear stress model suggests the possibility of twin parasites, and their existence on particular volcanoes verifies the possible validity of this interpretation though it may be not necessarily universally applicable to every volcano due to various effects of volcanism and lack of complexity in the model. Some characteristics of parasitic eruptions are discussed, such as monogenetic activity of parasitic vents and simultaneous eruptions of summit craters and parasitic vents. Parasitic volcanism proves to be not merely an auxiliary feature of its parental volcano but closely correlated with magma plumbing systems.
A first look at the Gargano (southern Italy) seismicity as seen by the local scale OTRIONS seismic network
Authors: Salvatore de Lorenzo  , Annalisa Romeo  , Luigi Falco  , Maddalena Michele  , Andrea Tallarico
Published: June 2021

On April 2013, a local scale seismic network, named OTRIONS, composed of twelve short period (1 Hz) three component seismometers, has been located in the northern part of the Apulia (southern Italy). In the first two months of data acquisition, the network recorded about one hundred very small (ML<2) magnitude earthquakes. A three-layer 1D VP velocity model was preliminarily computed, using the recordings of earthquakes occurred in the area in the period 2006-2012 and recorded by the national seismic network of INGV (Istituto Nazionale di Geofisica e Vulcanologia). This model was calibrated by means of a multi-scale approach, based on a global search of the minimum misfit between observed and theoretical travel times. At each step of the inversion, a grid-search technique was implemented to infer the elastic properties of the layers, by using HYPO71 to compute the forward models. In a further step, we used P and S travel times of both INGV and OTRIONS events to infer a minimum 1D VP velocity model, using a classical linearized inversion approach. Owing to the relatively small number of data and poor coverage of the area, in the inversion procedure, the VP/VS ratio was fixed to 1.82, as inferred from a modified Wadati diagram. The final 1D velocity model was obtained by averaging the inversion results arising from nine different initial velocity models. The inferred VP velocity model shows a gradual increase of P wave velocity with increasing the depth. The model is well constrained by data until to a depth of about 25-30 km.
Shift of effective lightning areas during pre to post period of solar cycle minimum of 2008-2009 as determined from Schumann resonance studies at Agra, India
Authors: Birbal Singh  , Devbrat Pundhir
Published: June 2021

Employing a set of 3-component search coil magnetometer, Schumann resonance studies have been in progress at Agra (Geograph. lat. 27.2°N, long. 78°E), India since 01 April, 2007. We have analysed the data for two periods; first from 01 April, 2007 to 31 March, 2008 (period-I), and then from 01 March, 2011 to 29 February, 2012 (period-II) which correspond to pre and post periods of solar cycle minimum of 2008-2009. From the diurnal variation of first mode intensity and frequency, we study the seasonal variations of global thunderstorm activity, effective source distance and level of lightning during both the periods. We show that world thunderstorm activity shifts to summer in the northern hemisphere as the effective source distance approaches close to the observer, and the level of intense lightning shifts from the month of July, 2007 in period-I to August, 2011 in period-II. This is supported by Lightning Imaging Sensor (LIS) satellite data also. A possible explanation in terms of increasing solar activity is suggested.
Detection of gravity changes before powerful earthquakes in GRACE satellite observations
Authors: Mohsen Shahrisvand  , Mehdi Akhoondzadeh  , Mohammad Ali Sharifi
Published: June 2021

The variations of gravity field have been analyzed in this article, in order to find disturbances in the vicinity of recent great earthquakes epicenters including Chile (February 27, 2010), Tohoku-Oki (March 11, 2011) and Indian Ocean (April 11, 2012) prior to the events. For this purpose, the 10 years long time series of gravitational gradient components obtained from weekly Gravity Recovery And Climate Experiment (GRACE) solutions have been used. Some of gravitational gradient components are independent to GRACE stripy error and amplify high frequency components of gravity field. Therefore that preseismic activity can be better illustrated. The interquartile method has been used to construct the higher and lower bounds in time series to detect outlying solution outside the bounds associated with impending earthquakes. Afterwards, Nonlinear Auto-Regressive models with eXogenous inputs (NARX) neural network has been proposed in the detection process of prominent gravity field anomalies prior the earthquakes. Both methods detect considerable anomalous occurrences during 2-5 weeks prior to the earthquakes. Our results statistics show that the anomalous deviations before the earthquakes have different signs and amplitudes at different cases.
Toward a cross-border early-warning system for Central Asia
Authors: Jacek Stankiewicz  , Dino Bindi  , Adrien Oth  , Stefano Parolai
Published: June 2021

Rapidly expanding urban areas in Central Asia are increasingly vulnerable to seismic risk; but at present, no earthquake early warning (EEW) systems exist in the region despite their successful implementation in other earthquake-prone areas. Such systems aim to provide short (seconds to tens of seconds) warnings of impending disaster, enabling the first risk mitigation and damage control steps to be taken. This study presents the feasibility of a large scale cross-border regional system for Central Asian countries. Genetic algorithms are used to design efficient EEW networks, computing optimal station locations and trigger thresholds in recorded ground acceleration. Installation of such systems within 3 years aims to both reducing the endemic lack of strong motion data in Central Asia that is limiting the possibility of improving seismic hazard assessment, and at providing the first regional earthquake early warning system in the area.
The contribution of EMCA to landslide susceptibility mapping in Central Asia
Authors: Annamaria Saponaro  , Marco Pilz  , Dino Bindi  , Stefano Parolai
Published: June 2021

Central Asia is one of the most exposed regions in the world to landslide hazard. The large variability of local geological materials, together with the difficulties in forecasting heavy precipitation locally and in quantifying the level of ground shaking, call for harmonized procedures to better quantify the hazard and the negative impact of slope failures across the Central Asian countries. As a first step towards a quantitative landslide hazard and risk assessment, a landslide susceptibility analysis at regional scale has been carried out, by benefitting of novel seismic hazard outcomes reached in the frame of Earthquake Model Central Asia (EMCA) project. By combining information coming from diverse potential factors, it is possible to detect areas where a potential for landslides exists. Initial results allow the identification of areas that are more susceptible to landslides with a level of accuracy greater than 70%. The presented method is, therefore, capable of supporting land planning activities at the regional scale in places where only scarce data are available.
Focus maps: a means of prioritizing data collection for efficient geo-risk assessment
Authors: Massimiliano Pittore
Published: June 2021

 

Efficient Disaster Risk Reduction (DRR) management constantly calls upon high-quality information to be collected or updated for vulnerability monitoring and risk assessment. This process is often resource- and time-intensive, which many economically developing states (including most Central Asian countries) can seldom afford. In this paper, we introduce the concept of focus maps as a useful tool to quantify the spatial probability of sampling. Focus maps allow for a data collection prioritization scheme to be put in place, enabling the realization of optimized spatial sampling which assigns a higher priority to locations where the need for high-quality information is greater. In practice, smaller samples can be drawn with the same (or better) resulting accuracy of the estimates, resulting in a more efficient use of time and resources. The factors that affect such a spatial sampling scheme include the usual components of risk assessment (hazard, exposure, vulnerability) where available, as well as other potentially critical factors, such as the extent and quality of previously collected data. The practical application of the proposed approach to the case of Central Asia will be exemplified and discussed.
“Scientist as a game”: learning geoscience via competitive activities
Authors: Gemma Musacchio  , Giovanna Lucia Piangiamore  , Giuliana D’Addezio  , Stefano Solarino  , Elena Eva
Published: June 2021

Nowadays, science communication is considered as one of the major challenges that research institutions are required to face. The strategies to attract public interest, the choice of the correct language, and the tools to trigger curiosity are a matter of debate. Research claims a concerning disaffection in older students toward science, which suggests that children are one of the major targets to whom the world of science and research should appeal. “Scientist as a game” is an experience of a hands-on approach that is combined with game-related challenges in the field of geoscience, where effective teaching methods require extensive research. This activity was held for the first time in the ‘Giacomo Doria’ City Museum of Natural History in Genoa as an open day laboratory, and it was linked to an interactive exhibition realized by Italy’s Istituto Nazionale di Geofisica e Vulcanologia (INGV). We set up four laboratory activities that were focused on: (1) where and why earthquakes and eruptions occur on Earth; (2) how volcanoes happen; (3) what the effect of shaking on buildings is; and (4) how to behave correctly in the case of an earthquake. Children were teamed up to score points according to the challenges included within each activity. The feedback of this experience was very positive, as shown by the questionnaires handed out to the participants immediately after each activity, and it reinforces the reviewed research on using games and hands-on activities in education.

 
Introduction of new data into the South African Ionospheric Map to improve the estimation of F2 layer parameters
Authors: Nicholas Ssessanga  , Lee-Anne McKinnell  , John Bosco Habarulema
Published: June 2021

In this paper the South African Ionospheric Map (SAIM) is upgraded with the usage of recent International Reference Ionosphere (IRI)-2012 model and South African Bottomside Model (SABIM) version 5 and validated for the critical frequency (foF2) of the F2 layer by comparing the model’s output with the measured ionosonde data. The SABIM model is also validated before use in the SAIM. The ionosonde stations used in the analysis include; Grahamstown (33.2°S, 26.3°E), Hermanus (34.4°S, 19.2°E), Louisvale (28.5°S, 21.2°E) and Madimbo (22.4°S, 30.9°E). The analysis of the results showed that the updates improved the performance of SAIM by 75% over the first version. The foF2 estimates from the SABIM version 5 model also gave a better estimate to the ionosonde measurements compared to the IRI-2012 model. The SABIM model performed 27% better than the IRI-2012 model during solar maximum and 14.7% better during solar minimum.
Seismic infrared anomalies detection in the case of the Wenchuan earthquake using bi-angular advanced along-track scanning radiometer data
Authors: Pan Xiong  , Xuhui Shen  , Xingfa Gu  , Qingyan Meng  , Liming Zhao  , Yanhua Zhao  , Yan Li  , Jianting Dong
Published: June 2021

The paper has developed Robust Satellite data analysis Technique (RST) to detect seismic anomalies in the case of the Wenchuan earthquake occurred on May 12, 2008, using the bi-angular Advanced Along-Track Scanning Radiometer (AATSR) gridded brightness temperature (BT) data based on spatial/temporal continuity and confutation analysis. The proposed method has been applied to analyze the Wenchuan earthquake with longitude from 95°E to 111°E and latitude from 23°N to 39°N, and a full data-set of 7 years data from 2003 to 2009 during the months of April and May has been analyzed. Combining with the rupture structure data of the Wenchuan earthquake, the analyzed results indicate that: the main structure activity (the Yingxiu-Beichuan fault) characteristics of the Wenchuan earthquake can be identified and extracted using the bi-angular AATSR nadir and forward brightness temperature data, and the seismic infrared radiation anomalies detected by the AATSR nadir brightness temperature is more close to the Yingxiu-Beichuan fault.
Ionospheric trends in Southern Hemisphere stations due to the increasing greenhouse gases concentration
Authors: José V. Venchiarutti  , Blas F. de Haro  , Ana G. Elías
Published: June 2021

The lower and middle atmosphere present long-term variations in temperature and other parameters linked to anthropogenic sources, such as the increase in greenhouse gases concentration since the start of the industrial era. Some examples are the well known temperature increase in the troposphere and stratosphere cooling. Upper atmosphere parameters also present long-term variations. While in the case of the middle and lower atmosphere it is debated whether the origin of the trends is primarily anthropogenic or solar, in the upper atmosphere other sources are also able to induce long-term changes, such as long-term variations in geomagnetic activity and secular variations of the Earth’s magnetic field. In this paper, trends of the F2 layer critical frequency, foF2, measured at three Southern Hemisphere stations (Brisbane, Canberra and Christchurch) are analyzed to determine the importance of increasing greenhouse gases concentration effect. According to our results for the period covering solar cycles 18 to 21 (period 1944-1986), it is more important than natural forcings. Update estimates including solar cycle 23 are presented although the difficulty due to two of the three stations present big data gaps during cycle 22 and traditional ionospheric filtering is no longer entirely reliable for cycle 23. The aim of this study is to contribute both to an active area of aeronomy as is the study of trends in the upper atmosphere, and to the understanding of climate change.
Characteristics of local earthquake seismograms of varying dislocation sources in a stratified upper crust and modeling for P and S velocity structure: comparison with observations in the Koyna-Warna region, India
Authors: V. G. Krishna
Published: June 2021

Vertical component record sections of local earthquake seismograms from a state-of-the-art Koyna-Warna digital seismograph network are assembled in the reduced time versus epicentral distance frame, similar to those obtained in seismic refraction profiling. The record sections obtained for an average source depth display the processed seismograms from nearly equal source depths with similar source mechanisms and recorded in a narrow azimuth range, illuminating the upper crustal P and S velocity structure in the region. Further, the seismogram characteristics of the local earthquake sources are found to vary significantly for different source mechanisms and the amplitude variations exceed those due to velocity model stratification. In the present study a large number of reflectivity synthetic seismograms are obtained in near offset ranges for a stratified upper crustal model having sharp discontinuities with 7%-10% velocity contrasts. The synthetics are obtained for different source regimes (e.g., strike-slip, normal, reverse) and different sets of source parameters (strike, dip, and rake) within each regime. Seismogram sections with dominantly strike-slip mechanism are found to be clearly favorable in revealing the velocity stratification for both P and S waves. In contrast the seismogram sections for earthquakes of other source mechanisms seem to display the upper crustal P phases poorly with low amplitudes even in presence of sharp discontinuities of high velocity contrasts. The observed seismogram sections illustrated here for the earthquake sources with strike-slip and normal mechanisms from the Koyna-Warna seismic region substantiate these findings. Travel times and reflectivity synthetic seismograms are used for 1-D modeling of the observed virtual source local earthquake seismogram sections and inferring the upper crustal velocity structure in the Koyna-Warna region. Significantly, the inferred upper crustal velocity model in the region reproduces the synthetic seismograms comparable to the observed sections for earthquake sources with differing mechanisms in the Koyna and Warna regions.
Orographic role in anomalous VHF propagation on the background of impending earthquakes (EQ)
Authors: Minakshi Devi  , Alaka Medhi  , Ananda Kumar Barbara  , Anna Depueva  , Yurij Ruzhin
Published: June 2021

The role of orographic factors in modifying atmospheric dynamics on the background of an impending earthquake (EQ) that might lead to propagation of a signal beyond the Line Of Sight (LOS) is examined in the paper. The analysis is based on the data of anomalous reception of VHF FM-signal at Gauhati University (GU, 26.15°N, 91.66°E), a station located in the sub Himalayan terrain. The signal reception records show that their anomalous appearance are associated closely with earthquake events of M >5.0, a phenomenon identified as EQ precursor. To identify sources of such reception, the paper presents some analytical approaches involving the terrain factors, impending EQ and atmospheric variabilities. Finally, the contribution of location/topography of the transmitter, receiver and epicenter in modifying the EQ induced atmospheric factors, is brought in to the ambit of analysis for explaining the observed over horizon VHF signal propagation. A special reference is made on the EQ time drop in temperature, increase in humidity and hence modification in Radio Refractive Index (RRI) gradient, in favoring such reception. A model in support of the observation on EQ time lithosphere-atmosphere coupling relevant to widening of radio horizon limit is also proposed.
Overview on the ‘Atmospheric Emissions from Volcanoes’ Special Issue
Authors: Shona Mackie  , Stefano Corradini  , Simona Scollo  , I. Mattew Watson
Published: June 2021

The session ‘Atmospheric Emissions from Volcanoes’ formed part of the 2014 General Assembly of the Europe-an Geosciences Union (EGU), held in Vienna from 27 April to 2 May. This special is-sue presents some of the work that was dis-cussed during the session. [...]
Annex 1 to: Trace elements mobility in soils from the hydrothermal area of Nisyros (Greece)
Authors: Kyriaki Daskalopoulou  , Sergio Calabrese  , Silvia Milazzo  , Lorenzo Brusca  , Sergio Bellomo  , Walter D'Alessandro  , Kostantinos Kyriakopoulos  , Franco Tassi  , Francesco Parello
Published: June 2021

Nisyros Island, Greece, is a stratovolcano known for its intense hydrothermal activity. On June 2013, during a multidisciplinary field campaign, soil samples were collected in the caldera area to determinate the main mineralogical assemblages and to investigate the distribution of trace element concentrations and the possible relationship to the contribution of fluids of deep origin. Soil samples were analysed with XRD and for the chemical composition of their leachable (deionized water) and pseudo total (microwave digestion)  [...]
Annex 3 to: Trace elements mobility in soils from the hydrothermal area of Nisyros (Greece)
Authors: Kyriaki Daskalopoulou  , Sergio Calabrese  , Silvia Milazzo  , Lorenzo Brusca  , Sergio Bellomo  , Walter D'Alessandro  , Kostantinos Kyriakopoulos  , Franco Tassi  , Francesco Parello
Published: June 2021

Mineralogical Assemblages [...]
Preface
Authors: Stefano Parolai  , Jochen Zschau  , Ulugbek Begaliev
Published: June 2021

Central Asia is one of the regions of the world with the highest seismic hazard. A number of large events have occurred in this region between the end of the 19th and the beginning of the 20th century, when urbanization was still limited. However, the recent increase in population and, in particular, the expansion of urban areas after the collapse of the Soviet Union has greatly increased the seismic risk of Central Asian countries. Within the framework of the Earthquake Model Central Asia (EMCA), the regional partnership of the Global Earthquake Model (GEM) for Central Asia, new Probabilistic Seismic Hazard models have been recently derived, along with site effects studies in several cities, and new models for exposure and vulnerability generated based on newly acquired data sets. This volume consist of 12 papers providing both an overview of the activities undertaken and a general description of the main results of the first phase of the EMCA initiative and of other projects that directly benefited from their cooperation with EMCA.
Variation of the Earth tide-seismicity compliance parameter during the recent seismic activity in Fthiotida, central Greece
Authors: Dimitrios N. Arabelos  , Michael E. Contadakis  , Georgios Vergos  , Spyrous Spatalas
Published: June 2021

Based on the results of our previous studies concerning the tidal triggering effect on the seismicity in Greece, we consider the confidence level of earthquake occurrence - tidal period accordance as an index of tectonic stress criticality, associated with earthquake occurrence. Then, we investigate whether the recent increase in the seismic activity at Fthiotida in Greek mainland indicates faulting maturity and the possible production a stronger earthquake. In this paper we present the results of this investigation.
The Italian reference site for TEM methods
Authors: Vincenzo Sapia  , Andrea Viezzoli  , Antonio Menghini  , Marco Marchetti  , Massimo Chiappini
Published: June 2021

The success of a long term transient electromagnetic survey (TEM) rigorously calls for appropriate system calibration, in addition to advanced processing and inversion of the measured data. In fact, acquisition of TEM data can be affected by a variety of noise sources from both inside and outside the system, making it difficult, for example, to define an absolute turn off time and/or to synchronize transmitter and receiver. For these reasons, a reference site plays an important role. As first step, we performed the calibration of a Geonics 47 at the Lyngby reference site in Denmark. We then set up a new reference site using the same calibrated TEM instrument. The reference site was established in the San Rossore park area (Pisa), where we identified an area that matches the required conditions. Subsequently, a series of TEM measurements were collected in the selected area using two pre-calibrated TEM instruments: the Geonics 47 and the WalkTEM respectively. The reference responses were therefore jointly inverted, obtaining a 5 layers model that was appointed to be the TEM reference model for the site. Afterwards, based on that reference model, we calibrated the Geonics 47 and 57 instruments for a 100 x 100 m central loop configuration. A unique time-shift and a data level shift factor was calculated and applied to the TEM system as result of the calibration procedure. The San Rossore TEM reference site is now available for anyone interested in calibrating TEM systems.
Sensitivities of surface wave velocities to the medium parameters in a radially anisotropic spherical Earth and inversion strategies
Authors: Sankar N. Bhattacharya
Published: June 2021

Sensitivity kernels or partial derivatives of phase velocity (c) and group velocity (U) with respect to medium parameters are useful to interpret a given set of observed surface wave velocity data. In addition to phase velocities, group velocities are also being observed to find the radial anisotropy of the crust and mantle. However, sensitivities of group velocity for a radially anisotropic Earth have rarely been studied. Here we show sensitivities of group velocity along with those of phase velocity to the medium parameters VSV, VSH , VPV, VPH , h and density in a radially anisotropic spherical Earth. The peak sensitivities for U are generally twice of those for c; thus U is more efficient than c to explore anisotropic nature of the medium. Love waves mainly depends on VSH while Rayleigh waves is nearly independent of VSH . The sensitivities show that there are trade-offs among these parameters during inversion and there is a need to reduce the number of parameters to be evaluated independently. It is suggested to use a nonlinear inversion jointly for Rayleigh and Love waves; in such a nonlinear inversion best solutions are obtained among the model parameters within prescribed limits for each parameter. We first choose VSH, VSV and VPH within their corresponding limits; VPV and h can be evaluated from empirical relations among the parameters. The density has small effect on surface wave velocities and it can be considered from other studies or from empirical relation of density to average P-wave velocity.
The study of equatorial plasma bubble during January to April 2012 over Kolhapur (India)
Authors: Parashram T. Patil  , Rupesh N. Ghodpage  , Alok K. Taori  , Rohit P. Patil  , Subramanian Gurubaran  , Suraj N. Nikte  , Dada P. Nade  , Ashok K. Sharma  , Sridhar Banola  , V. Lakshmi Narayanan  , Devendraa Siingh
Published: June 2021

Over 53 nights of all sky airglow imager data collected during January-April 2012 from the low latitude station Kolhapur (16.68°N, 74.26°E; 10.6°N dip latitude) have been analyzed to study the F-region dynamics through the imaging of OI 630 nm emission line. The observed night airglow data were supported by the ionosonde measurements from Tirunelveli (8.7°N, 77.8°E; 0.51°N dip latitude). Well defined magnetic field aligned depletions were observed during the observation period. Out of 53 nights, 40 nights exhibited the occurrence of north-south aligned equatorial plasma bubbles. These plasma bubbles were found moving towards east with drift speed in range between 70 to 200 m s-1. We have analyzed the zonal drift velocity variation and relation of bubble occurrence with the base height of the ionosphere together with the effects of the geomagnetic Ap and solar flux F10.7 cm index in its first appearance.
AC and DC global electric circuit properties and the height profile of atmospheric conductivity
Authors: Irina G. Kudintseva  , Alexander P. Nickolaenko  , Michael J. Rycroft  , Anna Odzimek
Published: June 2021

An apparent discrepancy is pointed out - at all heights, and by up to an order of magnitude - between the height profiles of atmospheric conductivity derived at AC using ELF propagation studies, especially from information on Schumann resonance of the Earth-ionosphere cavity, and using a model of the DC global atmospheric electric circuit. This serious issue is resolved by creating a hybrid profile of these two mid-latitude profiles, the first of which refers to conditions by day and the second by night. This hybrid profile is thus a first order attempt to represent globally averaged conditions. Close to the Earth’s surface, where the resistance of the atmosphere is largest, the properties of the DC global model exert the greatest influence, whereas in the middle atmosphere, at heights between 40 and 100 km, full wave computations show that the AC results are the more crucial. The globally averaged hybrid profile presented here has some limitations, and the physical reasons for these are addressed. They are due to the presence of aerosol particles of ice and/or of meteoric material which reduce the ionospheric D-region conductivity by an order of magnitude over only ~2 km of height, thereby causing ledges of ionisation. In the context of the globally averaged profile, published observations of the ionospheric effects of the giant gamma-ray flare from SGR 1806-20 (a neutron star having an enormously large magnetic field) occurring at 21:30 U.T. on December 27, 2004, are briefly discussed.
Origin of calderas: discriminating between collapses and explosions
Authors: Izumi Yokoyama
Published: June 2021

Origins of calderas may differ according to their subsurface structure that may be characterized by high or low density deposits that may be observed as high or low gravity anomalies, respectively. In the Introduction, the pioneering work of Fouqué[1879] on Santorini caldera is referred to in relation to definition of calderas. First, our discussion is focused on four calderas that were seen forming during the period from 1815 (the Tambora eruption) to 1991 (the Pinatubo eruption). Coincidently, these four calderas are all low-gravity-anomaly type. Their formation processes and subsurface structure are summarized by the existing data analyzed by various authors. These results are confirmed by results of drillings at some other calderas. Then, caldera formation of both types is discussed: High-gravity-anomaly-type calderas are expected to originate from subsidence of high-density ejecta into the summit magma reservoir. On the calderas of this type, the genetic eruptions believed to be accompanied by subsidences were not actually observed, and consequently three examples are mentioned only briefly. The low-gravity-anomaly-type calderas are discussed from standpoint of both the models of collapses and explosions. It is also emphasized that dynamic pressure ofexplosions is an important factor in the caldera formation, not only volume of the ejecta. To confirm the possibility that volcanic ejecta and edifices collapse into magma reservoirs, we discuss stress propagation from a depleted reservoir upward towards the Earth surface. Formation mechanisms of large calderas of this type are speculated; large calderas measuring about 20 km across may develop by successive merging of component calderas over a long period of times. A Kamchatka caldera under enlargement during the Holocene period is interpreted by successive merging of five component calderas.
Geophysical interpretation of GPS loading deformation over western Europe using GRACE measurements
Authors: Songyun Wang  , Jianli Chen  , Jin Li  , Xiaogong Hu  , Shengnan Ni
Published: June 2021

We analyze more than 10 years of Global Positioning System (GPS) height residuals and vertical displacements predicted from surface mass loading observed by the Gravity Recovery and Climate Experiment (GRACE) for 36 International GNSS Service (IGS) stations over Europe. Seasonal surface displacements, mostly due to atmospheric and hydrological loading, are significant in both GPS and GRACE measurements. With an extended time period, our new analysis based on release 05 GRACE data from Center for Space Research (CSR) shows considerably improved agreement between GPS and GRACE than that from previous studies, for not only annual but also interannual signals. The GPS height residual series at most stations exhibit reduced weighted root-mean-squares (WRMS) after removing GRACE-derived vertical displacements, which is attributed to improved accuracy of both GPS and GRACE data products. Furthermore, we demonstrate the necessity of reducing leakage bias in GRACE estimates for the study of surface loading deformation using GRACE satellite gravity observations.
Estimation of geomagnetic activity using measure of anomalousness
Authors: Anatoly Soloviev  , Sergey Agayan  , Shamil Bogoutdinov
Published: June 2021

Herein, we present a newly developed indicator for estimating geomagnetic activity. It is based on the magnitude of measure of anomalousness (MA) of magnetometer recordings at a given time or interval. It is intended for automated estimation of geomagnetic activity level in the area of a specific magnetic station or in a given region using data of a set of stations. It reflects geomagnetic activity level at different observatories in a single scale [-1, 1], regardless of their latitudinal location and consequently typical disturbance amplitudes. To a certain extent MA indicator is an analog of traditional K index. However, a well-known shortcoming of the latter is its long, 3-hour update rate. Moreover, K index calculation requires subtraction of Sq variation that also causes delays. At the same time there is a demand for operational geomagnetic indices that have maximal time resolution and are available in near real-time. The proposed MA indicator aims to address the shortcomings of the traditional K index. The MA calculation may be implemented automatically with the same time resolution as the initial data are recorded.
Site effect studies following the 2016 Mw 6.0 Amatrice Earthquake (Italy): the Emersito Task Force activities
Authors: Giovanna Cultrera  , Ezio D'Alema  , Sara Amoroso  , Barbara Angioni  , Paola Bordoni  , Luciana Cantore  , Fabrizio Cara  , Arrigo Caserta  , Rocco Cogliano  , Maria D'Amico  , Giuseppe Di Giulio  , Deborah Di Naccio  , Daniela Famiani  , Chiara Felicetta  , Antonio Fodarella  , Sara Lovati  , Lucia Luzi  , Marco Massa  , Alessia Mercuri  , Giuliano Milana  , Francesca Pacor  , Marta Pischiutta  , Stefania Pucillo  , Rodolfo Puglia  , Gaetano Riccio  , Gabriele Tarabusi  , Maurizio Vassallo  , Claudia Mascandola
Published: June 2021

On August 24, 2016, at 01:36 UTC a MW 6.0 earthquake struck an extensive area of the Central Apennines (Italy). It was followed by a large aftershock (MW 5.3, August 24, 02:33 UTC) and about 20 earthquakes with magnitude greater than 4.0, located between the towns of Norcia and Amatrice. Due to the mainshock magnitude and the widespread damaging level of buildings in the epicentral area, the Emersito task force has been mobilized by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The aim of Emersito is to carry out and coordinate the monitoring of local site effects, caused by geological and geomorphological settings. During the first days of the seismic emergency, Emersito installed a temporary seismic network for site effect studies at 4 municipalities close to the epicentral area (Amandola, Civitella del Tronto, Montereale and Capitignano), using 22 stations equipped with both velocimetric and accelerometric sensors. The selection of the sites where stations have been installed was mainly driven by the proximity to the epicentral area (without interfere with the rescue operation) and by peculiar geologic and geomorphologic settings (topographic irregularities, fault zones, alluvial plains).
What is the impact of the August 24, 2016 Amatrice earthquake on the seismic hazard assessment in central Italy?
Authors: Maura Murru  , Matteo Taroni  , Aybige Akinci  , Giuseppe Falcone
Published: June 2021

The recent Amatrice strong event (Mw6.0) occurred on August 24, 2016 in Central Apennines (Italy) in a seismic gap zone, motivated us to study and provide better understanding of the seismic hazard assessment in the macro area defined as “Central Italy”. The area affected by the sequence is placed between the Mw6.0 1997 Colfiorito sequence to the north (Umbria-Marche region) the Campotosto area hit by the 2009 L’Aquila sequence Mw6.3 (Abruzzo region) to the south. The Amatrice earthquake occurred while there was an ongoing effort to update the 2004 seismic hazard map (MPS04) for the Italian territory, requested in 2015 by the Italian Civil Protection Agency to the Center for Seismic Hazard (CPS) of the Istituto Nazionale di Geofisica e Vulcanologia INGV. Therefore, in this study we brought to our attention new earthquake source data and recently developed ground-motion prediction equations (GMPEs). Our aim was to validate whether the seismic hazard assessment in this area has changed with respect to 2004, year in which the MPS04 map was released. In order to understand the impact of the recent earthquakes on the seismic hazard assessment in central Italy we compared the annual seismic rates calculated using a smoothed seismicity approach over two different periods; the Parametric Catalog of the Historical Italian earthquakes (CPTI15) from 1871 to 2003 and the historical and instrumental catalogs from 1871 up to 31 August 2016. Results are presented also in terms of peak ground acceleration (PGA), using the recent ground-motion prediction equations (GMPEs) at Amatrice, interested by the 2016 sequence.
Fossil landscapes and youthful seismogenic sources in the central Apennines: excerpts from the 24 August 2016, Amatrice earthquake and seismic hazard implications
Authors: Gianluca Valensise  , Paola Vannoli  , Roberto Basili  , Lorenzo Bonini  , Pierfrancesco Burrato  , Michele Matteo Cosimo Carafa  , Umberto Fracassi  , Vanja Kastelic  , Francesco Emanuele Maesano  , Mara Monica Tiberti  , Gabriele Tarabusi
Published: June 2021

We show and discuss the similarities among the 2016 Amatrice (Mw 6.0), 1997 Colfiorito-Sellano (Mw 6.0-5.6) and 2009 L’Aquila (Mw 6.3) earthquakes. They all occurred along the crest of the central Apennines and were caused by shallow dipping faults between 3 and 10 km depth, as shown by their characteristic InSAR signature. We contend that these earthquakes delineate a seismogenic style that is characteristic of this portion of the central Apennines, where the upward propagation of seismogenic faults is hindered by the presence of pre-existing regional thrusts. This leads to an effective decoupling between the deeper seismogenic portion of the upper crust and its uppermost 3 km.The decoupling implies that active faults mapped at the surface do not connect with the seismogenic sources, and that their evolution may be controlled by passive readjustments to coseismic strains or even by purely gravitational motions. Seismic hazard analyses and estimates based on such faults should hence be considered with great caution as they may be all but representative of the true seismogenic potential.
Characteristics of the Strong Ground Motion from the 24th August 2016 Amatrice Earthquake
Authors: Marta Pischiutta  , Aybige Akinci  , Luca Malagnini  , André Herrero
Published: June 2021

The 2016 August 24 Amatrice earthquake occurred at 03:36 local time in Central Apennines Italy with an epicentre at 43.36°E, 38.76°N, Istituto Nazionale di Geofisica e Vulcanologia (INGV), few kilometers north of the city of Amatrice. The earthquake ruptured a North-West (NW)–South-East (SE) oriented normal fault dipping toward the South-West (SW) (Scognamiglio et al., 2016). High values of peak ground acceleration (~0.45 g) were observed close to Amatrice (3 stations being few kilometer distances from the fault). The present study presents an overview of the main features of the seismic ground shaking during the Amatrice earthquake. We analyze the ground motion characteristics of the main shock in terms of peak ground acceleration (PGA), peak ground velocity (PGV) and spectral accelerations (SA, 5 per cent of critical damping). In order to understand the characteristics of the ground motions induced by Amatrice earthquake, we also study the source-related effects relative to the fault rupture directivity.
Fast 3D seismic wave simulations of 24 August 2016 Mw 6.0 central Italy earthquake for visual communication
Authors: Emanuele Casarotti  , Federica Magnoni  , Licia Faenza  , Francesca Comunello  , Piero Polidoro  , Simone Mulargia
Published: June 2021

We present here the first application of the fast reacting framework for 3D simulations of seismic wave propagation generated by earthquakes in the Italian region with magnitude Mw 5. The driven motivation is to offer a visualization of the natural phenomenon to the general public but also to provide preliminary modeling to expert and civil protection operators. We report here a description of this framework during the emergency of 24 August 2016 Mw 6.0 central Italy Earthquake, a discussion on the accuracy of the simulation for this seismic event and a preliminary critical analysis of the visualization structure and of the reaction of the public.
Source identification for situational awareness of August 24th 2016 Central Italy event
Authors: Christian Bignami  , Cristiano Tomolei  , Giuseppe Pezzo  , Francesco Guglielmino  , Simone Atzori  , Elisa Trasatti  , Andrea Antonioli  , Salvatore Stramondo  , Stefano Salvi
Published: June 2021

On August 24, 2016, at 01:36 UTC a ML 6.0 earthquake struck a portion of the Central Apennines between the towns of Norcia and Amatrice. The epicentre was located near the town of Accumoli. Prompt Synthetic Aperture Radar (SAR) acquisitions and the available scientific knowledge of the area allowed to elaborate a first interpretative framework of the ongoing seismic sequence only 30 hours after the mainshock (doi: 10.5281/zenodo.60938) and a second analysis, complete of several Interferometric SAR (InSAR) data within two weeks (doi: 10.5281/zenodo.61682). Through the inversion of InSAR data, we found that the seismogenic structure is oriented NNW-SSE and extends about 20 km between the towns of Norcia and Amatrice with a width of about 10 km. The retrieved slip reaches a maximum value of more than 1.2 m, and stops at a depth of about 4 km. Preliminary fault slip inversions suggest two main patches of co-seismic deformation located NW and SE of the hypocenter. As a final result, we highlight the double fold achievements obtained: a rapid fault identification, and no disadvantage in terms of reliability of the retrieved parameters.