Showing papers in "Annals of Geophysics in 2014"
TL;DR: Most of the included events have a high reliability value which makes the Euro-Mediterranean Tsunami Catalogue an essential tool for the implementation of tsunami hazard and risk assessment.
Abstract: A unified catalogue containing 290 tsunamis generated in the European and Mediterranean seas since 6150 B.C. to current days is presented. It is the result of a systematic and detailed review of all the regional catalogues available in literature covering the study area, each of them having their own format and level of accuracy. The realization of a single catalogue covering a so wide area and involving several countries was a complex task that posed a series of challenges, being the standardization and the quality of the data the most demanding. A “reliability” value was used to rate equally the quality of the data for each event and this parameter was assigned based on the trustworthiness of the information related to the generating cause, the tsunami description accuracy and also on the availability of coeval bibliographical sources. Following these criteria we included in the catalogue events whose reliability ranges from 0 (“very improbable tsunami”) to 4 (“definite tsunami”). About 900 documentary sources, including historical documents, books, scientific reports, newspapers and previous catalogues, support the tsunami data and descriptions gathered in this catalogue. As a result, in the present paper a list of the 290 tsunamis with their main parameters is reported. The online version of the catalogue, available at http://roma2.rm.ingv.it/en/faci lities/data_bases/52/catalogue_of_the_euro-mediterranean_tsunamis, provides additional information such as detailed descriptions, pictures, etc. and the complete list of bibliographical sources. Most of the included events have a high reliability value (3= “probable” and 4= “definite”) which makes the Euro-Mediterranean Tsunami Catalogue an essential tool for the implementation of tsunami hazard and risk assessment.
92 citations
TL;DR: In this article, the authors used calibrated images collected by the video-surveillance system of the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, to retrieve the height of the eruption column during the recent Etna explosive activity.
Abstract: In this paper, we use calibrated images collected by the video-surveillance system of the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, to retrieve the height of the eruption column during the recent Etna explosive activity. The analysis is carried out on nineteen lava fountains from the New South East Crater dataset. The novel procedure described in this work is achieved in three main steps: at first we calibrated the camera, then we selected the images which recorded the maximum phase of the eruptive activity, and finally we applied an appropriate correction to account for the plume projection on the camera line of sight due to the wind. The results show that the column altitudes range between 6 and 9 km (upper limit of the camera system). The comparison with the plume height values estimated from the analysis of several SEVIRI and MODIS satellite images, show a good agreement. Finally, for nine events we also evaluated the thickness of the volcanic plumes in the umbrella region which ranges between 2 and 3 km.
78 citations
TL;DR: In this paper, the authors provide an overview of the continuous GPS monitoring of the Campi Flegrei caldera from January 2000 to July 2013, including network operations, data recording and processing, and data products.
Abstract: The Campi Flegrei caldera is an active volcanic system associated to a high volcanic risk, and represents a well known and peculiar example of ground deformations (bradyseism), characterized by intense uplift periods, followed by subsidence phases with some episodic superimposed mini-uplifts. Ground deformation is an important volcanic precursor, and, its continuous monitoring, is one of the main tool for short time forecast of eruptive activity. This paper provides an overview of the continuous GPS monitoring of the Campi Flegrei caldera from January 2000 to July 2013, including network operations, data recording and processing, and data products. In this period the GPS time series allowed continuous and accurate tracking of ground deformation of the area. Seven main uplift episodes were detected, and during each uplift period, the recurrent horizontal displacement pattern, radial from the “caldera center”, suggests no significant change in deformation source geometry and location occurs. The complete archive of GPS time series at Campi Flegrei area is reported in the Supplementary materials. These data can be usefull for the scientific community in improving the research on Campi Flegrei caldera dynamic and hazard assessment.
70 citations
TL;DR: In this article, the variation of total electron content (TEC) using Global Positioning System (GPS) satellites from four equatorial to mid-latitudes stations over a period of one year was investigated.
Abstract: The present study investigates the variation of Total Electron Content (TEC) using Global Positioning System (GPS) satellites from four equatorial to mid-latitudes stations over a period of one year. The stations are Port Blair (11.63°N, 92.70°E), Agartala (23.75°N, 91.25°E), Lhasa (29.65°N, 91.10°E) and Urumqi (43.46°N, 87.16°E). The diurnal, monthly and seasonal variations of TEC have been explored to study its latitudinal characteristics. Analysis of TEC data from these stations reveals the characteristics of latitudinal variation of Equatorial Ionospheric Anomaly (EIA). To validate the latest IRI 2012 model, the monthly and seasonal variations of GPS-TEC at all the four stations have been compared with the model for three different topside options of electron density, namely, NeQuick, IRI-01-corr and IRI-2001. TEC predictions from IRI-2001 top side electron density option using IRI 2012 model overestimates the observed TEC especially at the low latitudes. TEC from IRI- NeQuick and IRI-01-corr options shows a tendency to underestimate the observed TEC during the day time particularly in low latitude region in the high solar activity period. The agreement between the model and observed values are reasonable in mid latitude regions. However, a discrepancy between IRI 2012 derived TEC with the ground based observations at low latitude regions is found. The discrepancy appears to be higher in low-latitude regions in comparison to mid latitude regions. It is concluded that largest discrepancy in TEC occur as a result of poor estimation of the hmF2 and foF2 from the coefficients.
46 citations
TL;DR: The Alto Tiberina Near Fault Observatory (TABOO) as mentioned in this paper is a research infrastructure devoted to studying preconditioned processes, slow and fast deformation along a fault system located in the upper Tiber Valley (northern Apennines), dominated by a 60 km long low-angle normal fault (Alto Tiberia, ATF) active since the Quaternary.
Abstract: The availability of multidisciplinary and high-resolution data is a fundamental requirement to understand the physics of earthquakes and faulting. We present the Alto Tiberina Near Fault Observatory (TABOO), a research infrastructure devoted to studying preparatory processes, slow and fast deformation along a fault system located in the upper Tiber Valley (northern Apennines), dominated by a 60 km long low-angle normal fault (Alto Tiberina, ATF) active since the Quaternary. TABOO consists of 50 permanent seismic stations covering an area of 120 × 120 km 2 . The surface seismic stations are equipped with 3-components seismometers, one third of them hosting accelerometers. We instrumented three shallow (250 m) boreholes with seismometers, creating a 3-dimensional antenna for studying micro-earthquakes sources (detection threshold is M L 0.5) and detecting transient signals. 24 of these sites are equipped with continuous geodetic GPS, forming two transects across the fault system. Geochemical and electromagnetic stations have been also deployed in the study area. In 36 months TABOO recorded 19,422 events with M L ≤ 3.8 corresponding to 23.36e-04 events per day per squared kilometres; one of the highest seismicity rate value observed in Italy. Seismicity distribution images the geometry of the ATF and its antithetic/synthetic structures located in the hanging-wall. TABOO can allow us to understand the seismogenic potential of the ATF and therefore contribute to the seismic hazard assessment of the area. The collected information on the geometry and deformation style of the fault will be used to elaborate ground shaking scenarios adopting diverse slip distributions and rupture directivity models.
41 citations
TL;DR: The ACE-FTS data set as mentioned in this paper provides profiles of temperature and volume mixing ratios (VMRs) of more than 30 atmospheric trace gas species, as well as 20 subsidiary isotopologues of the most abundant trace atmospheric constituents over a latitude range of ~85°N to ∼85°S.
Abstract: On 12 August 2003, the Canadian-led Atmospheric Chemistry Experiment (ACE) was launched into a 74° inclination orbit at 650 km with the mission objective to measure atmospheric composition using infrared and UV-visible spectroscopy (Bernath et al. 2005). The ACE mission consists of two main instruments, ACE-FTS and MAESTRO (McElroy et al. 2007), which are being used to investigate the chemistry and dynamics of the Earth’s atmosphere. Here, we focus on the high resolution (0.02 cm-1) infrared Fourier Transform Spectrometer, ACE-FTS, that measures in the 750-4400 cm-1 (2.2 to 13.3 µm) spectral region. This instrument has been making regular solar occultation observations for more than nine years. The current ACE-FTS data version (version 3.0) provides profiles of temperature and volume mixing ratios (VMRs) of more than 30 atmospheric trace gas species, as well as 20 subsidiary isotopologues of the most abundant trace atmospheric constituents over a latitude range of ~85°N to ~85°S. This letter describes the current data version and recent validation comparisons and provides a description of our planned updates for the ACE-FTS data set. [...]
38 citations
TL;DR: In this article, two main fault systems, incompatible with a single stress field, were identified at Graciosa Island and it was proposed that the region is affected by two alternating stress fields.
Abstract: Graciosa is a mid-Pleistocene to Holocene volcanic island that lies in a complex plate boundary between the North American, Eurasian, and Nubian plates. Large fault scarps displace the oldest (Middle Pleistocene) volcanic units, but in the younger areas recent volcanism (Holocene to Upper Pleistocene) conceals the surface expression of faulting, limiting neotectonic observations. The large displacement accumulated by the older volcanic units when compared with the younger formations suggests a variability of deformation rates and the possibility of alternating periods of higher and lower tectonic deformation rates; this would increase the recurrence interval of surface rupturing earthquakes. Nevertheless, in historical times a few destructive earthquakes affected the island attesting for its seismic hazard. Regarding the structural data, two main fault systems, incompatible with a single stress field, were identified at Graciosa Island. Thus, it is proposed that the region is affected by two alternating stress fields. The stress field #1 corresponds to the regional stress regime proposed by several authors for the interplate shear zone that constitutes the Azorean segment of the Eurasia-Nubia plate boundary. It is suggested that the stress field #2 will act when the area under the influence of the regional stress field #1 narrows as a result of variations in the differential spreading rates north and south of Azores. The islands closer to the edge of the sheared region will temporarily come under the influence of a different (external) stress field (stress field #2). Such data support the concept that, in the Azores, the Eurasia-Nubia boundary corresponds to a complex and wide deformation zone, variable in time.
29 citations
TL;DR: In this paper, the authors proposed a method to estimate the seismic hazard of a given region from deformed sediments or rocks, beyond the limited temporal resolution of instrumental and historical seismicity, by measuring geologically recorded slip on active faults.
Abstract: Earthquake geology studies the effects, the me-chanics and the impacts of earthquakes in the geologi-cal environment. Its role is also to decode the faulthistory, therefore its approach is fault specific and itsoutcomes are of decisive value for seismic hazard as-sessment and planning. The term Earthquake geologyincludes aspects of modern instrumental studies, tec-tonics and structural geology, historical surface defor-mation and tectonic geomorphology, whereas paleo-seismology is considered part of earthquake geology[McCalpin 2009]. In a broader sense, paleoseismologyintends to establish the seismic history of a given faultor given region from deformed sediments or rocks, be-yond the limited temporal resolution of instrumentaland historical seismicity [e.g., Audemard and Michetti2011]. The advances of Earthquake geology and paleo-seismology over the last few decades offered a quanti-tative description of Earthquake Environmental Effectsthat led to the development of the Environmental Seis-mic Intensity Scale ESI 2007 [Michetti et al. 2007].Seismic hazard assessment is predominantly basedon the instrumental and historical catalogues of seis-micity. However, these catalogues are incomplete andhave an inhomogeneity of geographical and temporalcoverage in terms of the seismic record, forming theirmain disadvantage. This is because historic cataloguesare generally too short (from several tens of years toseveral hundreds of years, depending on the country)compared to the recurrence interval of particular faults(ranging from a few hundred years to several thousandsof years) [Goes 1996, Yeats and Prentice 1996, Machette2000, Valensise and Pantosti 2001]. The latter impliesthat the sample from the historical record is incompleteand that a large number of faults would not have rup-tured during the completeness period of the historicalrecord. For example, Greece has one of the longest his-torical catalogues worldwide with the oldest recordedevents in 550 B.C. However, this catalogue is consideredcomplete for events M≥7.3 since 1500 and for M≥6.5only since 1845 [Papazachos et al. 2000]. In addition,maps based on historical seismicity can give erroneouspictures of the present day hazard. A low seismicityzone on such a map, representing low hazard, may de-lineate a seismic gap (i.e., a gap that an impeding earth-quake will cover) and actually be a place of high presentand future hazard [Scholz 2002]. On the other hand, aregion that has recently experienced a damaging earth-quake, and hence is represented as high hazard on amap, actually may be a region of low hazard in the nearfuture because it is now at an early stage in a new seis-mic cycle [Scholz 2002].Geological data have the potential to extend thehistory of slip on a fault back many thousands of years,a time span that generally encompasses a large numberof earthquake cycles [Yeats and Prentice 1996], and thuselucidates the long-term pattern of fault-slip. As a re-sult, fault specific approaches are becoming very im-portant for seismic hazard assessment, by providingquantitative assessments through measurement of ge-ologically recorded slip on active faults, sampling muchgreater periods of time and providing a more reliableestimate of hazard than the historical earthquakerecord [e.g., Yeats and Prentice 1996, Michetti et al.2005]. In addition, geologic fault slip-rate data offercomplete spatial coverage, providing higher spatial res-olution than traditional seismic hazard maps based onhistorical/instrumental records [Boncio et al. 2004,Roberts et al. 2004, Pace et al. 2010, Papanikolaou et al.2013]. For land-use planning and critical facilities or in-surance risk evaluation purposes, a higher spatial reso-lution is also desirable.During the last years, a number of major earth-quakes and mega-earthquakes occurred at plate bound-
20 citations
TL;DR: In this article, a study of marine terraces along the coastline of Portugal was conducted to identify regional vertical crustal motions and to better understand the recent tectonic activity in this sector of Iberia, and to search for evidence for deformation that may relate to inferred offshore active structures.
Abstract: Southwest mainland Portugal is located close to the Eurasia-Nubia plate boundary and is characterized by moderate seismicity, although strong events have occurred as in 1755 (Mw≥8), 1969, (Mw 7.9), and more recently in 2007 (Mw 5.9) and 2009 (Mw 5.5), all located in the offshore. No historical earthquakes with onshore rupture are known for this region. At the coastline, high sea cliffs, incised drainages, emergent marine abrasion platforms and paleo sea cliffs indicate that this region is undergoing uplift, although no morphological features were found that could be unequivocally associated with the 1755 mega earthquake. To better understand the recent tectonic activity in this sector of Iberia, it is necessary not only to analyze active structures on land, but also to search for evidence for deformation that may relate to inferred offshore active structures. We thus conducted a study of marine terraces along the coastline to identify regional vertical crustal motions. Several poorly preserved surfaces with thin sedimentary deposits, comprising old beach sediments, were recognized at elevations starting at 2 m elevation and rising inland up to a regional abrasion platform situated at about 120 m a.s.l.. We identified distinct paleo sea level references at several locations at consistent elevations. This terrace sequence is likely Late Pleistocene in age, with individual platforms correlative to MIS 5 high stands and is coherent with a long-term slow uplift of the littoral zone for the southwest of Portugal. Although dating of discrete platforms is an ongoing and difficult task, preliminary correlations of paleo-shoreline elevations suggest that the uplift rate is in the range of 0.1-0.2 mm/yr.
18 citations
TL;DR: In this article, the effect of nine distinct storms on the occurrence of ionospheric irregularities at Fraceville in Gabon (Lat = −1.63˚, Long = 13.55˚ and dip lat. = −15.94˚) was studied.
Abstract: Large-scale ionospheric irregularities usually measured by GPS TEC fluctuation indices are regular occurrence at the equatorial region shortly after sunset around solar maximum. Magnetic storm can trigger or inhibit the generation of these irregularities depending on the local time the main phase of a particular storm occurs. We studied the effect of nine (9) distinct storms on the occurrence of ionospheric irregularities at Fraceville in Gabon (Lat = −1.63˚, Long = 13.55˚, dip lat. = −15.94˚), an equatorial station in the African sector. These storms occurred between November 2001 and September 2002. We used TEC fluctuation indices (i.e. ROTI and ROTIAVE) estimated from 30 s interval Rinex data and also we used the storm indices (i.e. Dst, dDst/dt, and IMF BZ) to predict the likely effect of each storm on the irregularities occurrence at this station. The results obtained showed that most of the storms studied inhibited ionospheric irregularities. Only one out of all the storms studied (i.e. September 4, 2002 storms with the main phase on the night of September 7-8) triggered post-midnight ionospheric irregularities. There are two of the storms during which ionospheric irregularities were observed. However, these may not be solely attributed to the storms event because the level of irregularities observed during these two storms is comparable to that observed during previous days before the storms. For this station and for the storms investigated, it seems like a little modification to the use of Aarons categories in terms of the local time the maximum negative Dst occurs could lead to a better prediction. However, it would require investigating many storms during different level of solar activities and at different latitudes to generalize this modification.
18 citations
TL;DR: The Measurements of Pollution in the Troposphere (MOPITT) instrument on the NASA Terra platform has now acquired over thirteen years of global tropospheric carbon monoxide (CO) observations, forming the longest satellite record for an important pollutant.
Abstract: The Measurements of Pollution in the Troposphere (MOPITT) instrument on the NASA Terra platform has now acquired over thirteen years of global tropospheric carbon monoxide (CO) observations, forming the longest satellite record for an important pollutant. [...]
TL;DR: In this paper, a correlation was found between the measured radon data and the seismic activity in the region and the method employed was useful for removing the effect of meteorological parameters and to identify radon maxima possibly caused by seismic activity.
Abstract: Soil radon data were recorded at two selected sites along Mat fault in Mizoram (India), which lies in the highest seismic zone in India. The study was carried out during July 2011 to May 2013 using LR-115 Type II films. Precursory changes in radon concentration were observed prior to some earthquakes that occurred around the measuring sites. Positive correlation was found between the measured radon data and the seismic activity in the region. Statistical analysis of the radon data together with the meteorological parameters was done using Multiple Regression Method. Results obtained show that the method employed was useful for removing the effect of meteorological parameters and to identify radon maxima possibly caused by seismic activity.
TL;DR: One year field experiment has started on December 2011 at the French - Italian station of Concordia at Dome C, East Antarctic Plateau as discussed by the authors, where a sodar was improved to achieve the vertical/time resolution needed to study the surface layer turbulent processes under stable/very stable stratifications.
Abstract: One year field experiment has started on December 2011 at the French - Italian station of Concordia at Dome C, East Antarctic Plateau. The objective of the experiment is the study of the surface layer turbulent processes under stable/very stable stratifications, and the mechanisms leading to the formation of the warming events. A sodar was improved to achieve the vertical/time resolution needed to study these processes. The system, named Surface Layer sodar (SL-sodar), may operate both in high vertical resolution (low range) and low vertical resolution (high range) modes. In situ turbulence and radiation measurements were also provided in the framework of this experiment. A few preliminary results, concerning the standard summer diurnal cycle, a summer warming event, and unusually high frequency boundary layer atmospheric gravity waves are presented.
TL;DR: In this paper, the autoregressive method was used to determine the frequencies of the singlets of seven spheroidal modes (0 S 2, 2 S 1, 0 S 3, 0 S 4, 1 S 2, 0S 0, and 3 S 1 ) and the degenerate frequencies of three toroidal modes ( 0 T 2, 0 T 3, and 0 T 4 ) below 1 mHz after two recent huge earthquakes, the 2010 Mw8.8 Maule earthquake and the 2011 Mw9.1 Tohoku earthquake.
Abstract: Based upon SG (superconducting gravimeter) records, the autoregressive method proposed by Chao and Gilbert [1980] is used to determine the frequencies of the singlets of seven spheroidal modes ( 0 S 2 , 2 S 1 , 0 S 3 , 0 S 4 , 1 S 2 , 0 S 0 , and 3 S 1 ) and the degenerate frequencies of three toroidal modes ( 0 T 2 , 0 T 3 , and 0 T 4 ) below 1 mHz after two recent huge earthquakes, the 2010 Mw8.8 Maule earthquake and the 2011 Mw9.1 Tohoku earthquake. The corresponding quality factors Qs are also determined for those modes, of which the Qs of the five singlets of 1 S 2 and the five singlets (m=0, m=±2, and m=±3) of 0 S 4 are estimated for the first time using the SG observations. The singlet m=0 of 3 S 1 is clearly observed from the power spectra of the SG time series without using other special spectral analysis methods or special time series of polar station records. In addition, the splitting width ratio R of 3 S 1 is 0.99, and consequently we conclude that 3 S 1 is normally split. The frequencies and Qs of the modes below 1mHz can contribute to refining the 3D density and attenuation models of the Earth.
TL;DR: In this paper, the authors analyzed the electromagnetic background noise at L'Aquila Geomagnetic Observatory during 2006 and 2007 in the frequency band 1-100 mHz and found that in our area the main source of artificial noise is constituted by the DC electrified railways.
Abstract: In this paper we analyze the electromagnetic background noise at L’Aquila Geomagnetic Observatory during 2006 and 2007 in the frequency band 1-100 mHz. In this band a pronounced daily variation is observed both in the natural signals as well as in the artificial ones, giving rise to the problem of separating different contributions of very similar morphology. We analyzed periods when the local K index was approximately zero, in correspondence with minimum of the magnetospheric and ionospheric activity. We found that in our area the main source of artificial noise is constituted by the DC electrified railways.
TL;DR: A sedimentary archive corresponding to the last 17 cal kyr BP has been studied by means of a giant piston core retrieved on board R/V MARION-DUFRESNE in the North Central Gulf of Corinth as mentioned in this paper.
Abstract: A sedimentary archive corresponding to the last 17 cal kyr BP has been studied by means of a giant piston core retrieved on board R/V MARION-DUFRESNE in the North Central Gulf of Corinth. Based on previous methodological improvements, grain-size distribution and Magnetic Susceptibility Anisotropy (MSA) have been analysed in order to detect earthquake-induced deposits. We indentified 36 specific layers -Homogenites+Turbidites (HmTu) - intercalated within continuous hemipelagictype sediments (biogenic or bio-induced fraction and fine-grained siliciclastic fraction). The whole succession is divided into a non-marine lower half and a marine upper half. The “events” are distributed through the entire core and they are composed of two terms: a coarse-grained lower term and an upper homogeneous fine-grained term, sharply separated. Their average time recurrence interval could be estimated for the entire MD01-2477 core. The non-marine and the marine sections yielded close estimated values for event recurrence times of around 400 yrs to 500 yrs.
TL;DR: In this article, structural damage and earthquake environmental effects (EEE) were induced in the NW Peloponnese, offering the opportunity to test and compare the ESI 2007 and the EMS-98 intensity scales in a moderate strike-slip event.
Abstract: On June 8, 2008, a strike-slip earthquake (Mw=6.4) was generated NE of the Andravida town (NW Peloponnese, western Greece) due to the activation of the previously unknown western Achaia strike-slip fault zone (WAFZ). Extensive structural damage and earthquake environmental effects (EEE) were induced in the NW Peloponnese, offering the opportunity to test and compare the ESI 2007 and the EMS-98 intensity scales in a moderate strike-slip event. No primary EEE were induced, while secondary EEE including seismic fractures, liquefaction phenomena, slope movements and hydrological anomalies were widely observed covering an area of about 800 km 2 . The lack of primary effects and the relatively small surface deformation with respect to the earthquake magnitude is due to the thick Gavrovo flysch layer in the affected area that isolated and absorbed the subsurface deformation from the surface. According to the application of the EMS-98 scale, damage to masonry buildings ranged from grade 3 to 5, while damage in most of R/C buildings ranged from grade 1 to 3. A maximum ESI 2007 intensity VIII-IX is recorded, while the maximum EMS-98 intensity is IX. For all the sites where intensity VIII has been recorded the ESI 2007 and the EMS-98 agree, but for others the ESI 2007 intensities values are lower by one or two degrees than the corresponding EMS-98 ones, as it is clearly concluded from the comparison of the produced isoseismals. An exception to this rule is the Valmi village, where considerable structural damage occurs (IX EMS-98 ) along with the lack of significant EEE (V ESI 2007 ). This variability between the ESI 2007 and the EMS-98 intensity values is predominantly attributed to the vulnerability of old masonry buildings constructed with no seismic resistance design. Correlation of all existing data shows that the geological structure, the active tectonics, and the geotechnical characteristics of the alpine and post-alpine formations along with the construction type of buildings were of decisive importance in the damage and the EEE distribution.
TL;DR: In this paper, two distinct mechanisms that cause Earth electricity are described, and a broad selection of current research is highlighted, as well as the strongest electric currents are related to lightning phenomena or space weather.
Abstract: Telluric currents are natural electrical phenomena in the Earth or its bodies of water. The strongest electric currents are related to lightning phenomena or space weather. Earth electricity can cause damage to structures, and may be useful for earthquake forecasting and other applications. Thirty-two distinct mechanisms that cause Earth electricity are described, and a broad selection of current research is highlighted.
TL;DR: In this paper, a total of 2100 VLF-EM data plus selected selected VES points were covered over 7 traverses with length varying from 3000 to 4500 m. Results of the investigation indicate that a HKH sounding curve is obtained with a maximum of five subsurface layers comprising: the top soil, clay/sandy clay unit, the fresh basement, fractured basement and the basement bedrock.
Abstract: In a hard rock environment with surface or near surface expression of outcrops, the use of VES only becomes difficult due to its associated problems and limitations. However, the use of VLF-EM becomes imperative in mapping basement structures relevant to groundwater development. A total of 2100 VLF-EM data plus selected VES points were covered over 7 traverses with length varying from 3000 to 4500 m. The VLF-EM result mapped basement structures relevant in groundwater development. This is further studied using VES. Results of the investigation indicate that a HKH sounding curve is obtained with a maximum of five subsurface layers comprising: the top soil, clay/sandy clay unit, the fresh basement, fractured basement and the basement bedrock. The fractured basement layer constitutes the main aquifer unit with thickness of 20-25 m. The layer resistivity and thickness ranges are 60-100 ohm-m; 40-80 ohm-m, 1600-2100 ohm-m, 250-420 ohm-m, and 2200-7500 ohm-m; and 0.3-1.2 m, 1.9-2.5 m, 16.5-22.5 m and 22-30 m for the five layers respectively. The geoelectric results compared favorably well with drilling information to above 90%. The yield of the well is 2 L/s with good recharge capability.
TL;DR: In this article, the authors made the most of the opportunities of the International Polar Year 2007-2008 to introduce advances in seismic monitoring along four lines: (1) the improvement of the seismic network installed for seismic monitoring during the summer surveys; (2) the development and improvement of seismic arrays for the detection and characterization of seismo-volcanic signals; (3) the design of automated event recognition tools, to simplify the process of data interpretation; and (4) the deployment of permanent seismic stations.
Abstract: Deception Island is an active volcano located in the south Shetland Islands, Antarctica. It constitutes a natural laboratory to test geophysical instruments in extreme conditions, since they have to endure not only the Antarctic climate but also the volcanic environment. Deception is one of the most visited places in Antarctica, both by scientists and tourists, which emphasize the importance of volcano monitoring. Seismic monitoring has been going on since 1986 during austral summer surveys. The recorded data include volcano-tectonic earthquakes, long-period events and volcanic tremor, among others. The level of seismicity ranges from quiet periods to seismic crises (e.g. 1992-1993, 1999). Our group has been involved in volcano monitoring at Deception Island since 1994. Based on this experience, in recent years we have made the most of the opportunities of the International Polar Year 2007-2008 to introduce advances in seismic monitoring along four lines: (1) the improvement of the seismic network installed for seismic monitoring during the summer surveys; (2) the development and improvement of seismic arrays for the detection and characterization of seismo-volcanic signals; (3) the design of automated event recognition tools, to simplify the process of data interpretation; and (4) the deployment of permanent seismic stations. These advances help us to obtain more data of better quality, and therefore to improve our interpretation of the seismo-volcanic activity at Deception Island, which is a crucial step in terms of hazards assessment.
TL;DR: In this paper, the results of a geochemical and isotopic survey carried out on these gas emissions from March 2009 to January 2014 are presented, where CO 2 fluxes from both the two well and soil from an area of about 653,500 m 2 located between them were measured.
Abstract: The Mt. Amiata volcano (Tuscany, central Italy) hosts the second largest geothermal field of Italy. Its SW and NE sectors are characterized by the presence of several CO 2 -rich (>95% by vol.) gas discharges. An intense Hg mining activity had taken place from the 19th century up to the end of the ’70s, particularly close to Abbadia San Salvatore, during which two drillings (Acqua Passante and Ermeta) intercepted a CO 2 -rich gas fertile horizon. The related gases are emitted in the atmosphere since 1938 and 1959, respectively, causing severe concerns for the local air quality. In this work the results of a geochemical and isotopic survey carried out on these gas emissions from March 2009 to January 2014 are presented. CO 2 fluxes from both the two wells and soil from an area of about 653,500 m 2 located between them were measured. The two wells are emitting up to 15,000, 92 and 8 tons y -1 of CO 2 , CH 4 and H 2 S, respectively, while the computed soil CO 2 output was estimated at 4,311 ton y -1 . The spatial distribution of the CO 2 soil flux suggests the presence of preferential patterns, indicating sites of higher permeability. Since the local municipality is evaluating the possibility to plug the Ermeta vent, a temporarily closure should first be carried out to test the possible influence of this operation on the diffuse soil degassing of deep-originated CO 2 in the surrounding area. This implies that diffuse soil gases should carefully be monitored before proceeding with its definitive closure.
TL;DR: In this paper, the authors present and discuss the results of 148 measurements of soil CO 2 flux performed for the first time in Linosa island (Sicily Channel, Italy), a Plio-Pleistocene volcanic complex no longer active but still of interest owing to its location within a seismically active portion of the Sicily Channel rift system.
Abstract: Herein, we present and discuss the result of 148 measurements of soil CO 2 flux performed for the first time in Linosa island (Sicily Channel, Italy), a Plio-Pleistocene volcanic complex no longer active but still of interest owing to its location within a seismically active portion of the Sicily Channel rift system. The main purpose of this survey was to assess the occurrence of CO 2 soil degassing, and compare flux estimations from this island with data of soil degassing from worldwide active volcanic as well as non-volcanic areas. To this aim soil CO 2 fluxes were measured over a surface of about 4.2 km 2 covering ~80% of the island. The soil CO 2 degassing was observed to be mainly concentrated in the eastern part of the island likely due to volcano-tectonic lineaments, the presence of which is in good agreement with the known predominant regional faults system. Then, the collected data were interpreted using sequential Gaussian simulation that allowed estimating the total CO 2 emissions of the island. Results show low levels of CO 2 emissions from the soil of the island (~55 ton d -1 ) compared with CO 2 emissions of currently active volcanic areas, such as Miyakejima (Japan) and Vulcano (Italy). Results from this study suggest that soil degassing in Linosa is mainly fed by superficial organic activity with a moderate contribution of a deep CO 2 likely driven by NWSE trending active tectonic structures in the eastern part of the island.
TL;DR: In this article, the authors used a Multi-component Gas Analyser System (Multi-GAS) to measure, for the very first time, the composition (H2O, CO2, H2S, SO2) of the volcanic gas plume issuing from the Boiling Lake, a vigorously degassing, hot volcanic lake in Dominica, West Indies.
Abstract: We used a Multi-component Gas Analyser System (Multi-GAS) to measure, for the very first time, the composition (H2O, CO2, H2S, SO2) of the volcanic gas plume issuing from the Boiling Lake, a vigorously degassing, hot (T ~ 80-90°C) volcanic lake in Dominica, West Indies. The Multi-GAS captured in-plume concentrations of H2O, CO2 and H2S were well above those typical of ambient atmosphere, while no volcanic SO2 was detected (<0.05 ppm). These were used to derive the Boiling Lake plume characteristic ratios of CO2/H2S (5.2±0.4) and H2O/CO2 (31.4±6). Assuming that other volcanic gas species (e.g., HCl, CO, H2, N2, etc.) are absent in the plume, we recalculated a (air-free) composition for the sourcing volcanic gases of ~ 96.3% H2O, 3.1% CO2 and 0.6% H2S. This hydrous gas composition is within the range of published gas compositions in the Lesser Antilles region, and slightly more H2O-rich than obtained for the fumaroles of the nearby Valley of Desolation (~94.4% H2O, 4.7% CO2 and 0.8% H2S; CO2/H2S of ~5.7). We use our results, in tandem with the output of numerical simulations of gas scrubbing in the lake-water (performed via the EQ3/6 software), to derive new constraints on the degassing mechanisms at this poorly studied (but potentially hazardous) volcanic lake.
TL;DR: In this article, the authors evaluated the ESI 2007 intensity for the main Kalamata earthquake, which is strongly related to the active fault zones and reactivated faults observed in the area as well as to the intense morphology of the activated Dimiova-Perivolakia graben, and concluded that both intensity scales fit in with the neotectonic regime of the area.
Abstract: On September 13, 1986, a shallow earthquake (Ms=6.2) struck the city of Kalamata and the surrounding areas (SW Peloponnese, Greece) resulting in 20 fatalities, over 300 injuries, extensive structural damage and many earthquake environmental effects (EEE). The main shock was followed by several aftershocks, the strongest of which occurred two days later (Ms=5.4). The EEE induced by the 1986 Kalamata earthquake sequence include ground subsidence, seismic faults, seismic fractures, rockfalls and hydrological anomalies. The maximum ESI 2007 intensity for the main shock has been evaluated as IX ESI 2007 , strongly related to the active fault zones and the reactivated faults observed in the area as well as to the intense morphology of the activated Dimiova-Perivolakia graben, which is a 2nd order neotectonic structure located in the SE margin of the Kalamata-Kyparissia mega-graben and bounded by active fault zones. The major structural damage of the main shock was selective and limited to villages founded on the activated Dimiova-Perivolakia graben (IX EMS-98 ) and to the Kalamata city (IX EMS-98 ) and its eastern suburbs (IX EMS-98 ) located at the crossing of the prolongation of two major active fault zones of the affected area. On the contrary, damage of this size was not observed in the surrounding neotectonic structures, which were not activated during this earthquake sequence. It is concluded that both intensity scales fit in with the neotectonic regime of the area. The ESI 2007 scale complemented the EMS-98 seismic intensities and provided a completed picture of the strength and the effects of the September 13, 1986, Kalamata earthquake on the natural and the manmade environment. Moreover, it contributed to a better picture of the earthquake scenario and represents a useful and reliable tool for seismic hazard assessment.
TL;DR: In this paper, the authors present the validation methodology developed for this project and show the first intercomparison results obtained for the Izana Atmospheric Observatory between 2008 and 2012, focusing on two of the most important greenhouse gases, CH 4 and N 2 O.
Abstract: Within the project VALIASI (VALidation of IASI level 2 products) the validation of the IASI operational atmospheric trace gas products (total column amounts of H 2 O, O 3 , CH 4 , N 2 O, CO 2 and CO as well H 2 O and O 3 profiles) will be carried out. Ground-based FTS (Fourier Transform Spectrometer) trace gas measurements made in the framework of NDACC (Network for the Detection of Atmospheric Composition Change) serve as the validation reference. In this work, we will present the validation methodology developed for this project and show the first intercomparison results obtained for the Izana Atmospheric Observatory between 2008 and 2012. As example, we will focus on two of the most important greenhouse gases, CH 4 and N 2 O.
TL;DR: In this article, a previously unnoticed anomaly in the long-term sea-level acceleration of the Baltic Sea tide gauge records is reported, and they explain it by the classical post-glacial rebound theory and numerical modeling of glacial isostasy.
Abstract: Observations from the global array of tide gauges show that global sea-level has been rising at an average rate of 1.5-2 mm/yr during the last ~150 years [Douglas 1991, Spada and Galassi 2012]. Although a global sea-level acceleration was initially ruled out [Douglas 1992], subsequent studies [Douglas 1997, Church and White 2006, Jevrejeva et al. 2008, Church and White 2011] have coherently proposed values of ~1 mm/year/century [Olivieri and Spada 2013]. More complex non-linear trends and abrupt sea-level variations have now also been recognized. Globally, these could manifest a regime shift between the late Holocene and the current rhythms of sea-level rise [Gehrels and Woodworth 2013], while locally they result from ocean circulation anomalies, steric effects and wind stress [Bromirski et al. 2011, Merrifield 2011]. Although isostatic readjustment affects the local rates of secular sea-level change [Milne and Mitrovica 1998, Peltier 2004], a possible impact on regional acceleration has been so far discounted [Douglas 1992, Jevrejeva et al. 2008, Woodworth et al. 2009] since the process evolves on a millennium time scale [Turcotte and Schubert 2002]. Here we report a previously unnoticed anomaly in the long-term sea-level acceleration of the Baltic Sea tide gauge records, and we explain it by the classical post-glacial rebound theory and numerical modeling of glacial isostasy. Contrary to previous assumptions, our findings demonstrate that isostatic compensation plays a role in the regional secular sea-level acceleration.
TL;DR: In this paper, the cumulative distribution of the TCLWC derived from radiosonde measurement in each climatic zone shows a departure from the ITU Study Group 3 data, with an exceedance percentage difference of 32% to 90% occurring 0.01% to 10% of the time.
Abstract: Cloud cover statistics, cloud base and top height, cloud temperature, frequency of precipitation, freezing height, total cloud liquid water content (TCLWC) and cloud attenuation data have been obtained for the six major climatic zones of Africa. The present results reveal a strong positive correlation between the monthly distribution of low cloud cover, cloud top height, cloud temperature, and frequency of precipitation in the six zones. The cumulative distribution of the TCLWC derived from radiosonde measurement in each climatic zone shows a departure from the TCLWC recommended by the ITU Study Group 3 data, with an exceedance percentage difference of 32% to 90% occurring 0.01% to 10% of the time. The underestimation of the TCLWC is greatest in the tropical rain forest. A comparison of the cloud attenuation cumulative distribution in the Ka and V bands reveals that the International Telecommunication Union – Region (ITU-R) is an intergovernmental organization that develops rain model based on collected data around the world. This model underestimates the cloud attenuation in all of the six climatic zones by 2.0 dB and 4.7 dB for the arid Sahara desert, 1.3 dB and 3.0 dB in semi-arid North Africa, 1.3 dB and 1.5 dB in savannah North Africa, 2.0 dB and 3.6 dB in the tropical rain forest, 1.3 dB and 2.9 dB in savannah South Africa and 0.9 dB and 2.6 dB in semi-arid South Africa, respectively, at 30 and 50 GHz. Overall, the cloud attenuation in the tropical rain-forest zone is very high because of the high annual total cloud cover (98%), high annual frequency of precipitation (4.5), low annual clear sky amount (8%), high cloud depth (10,937 m), high 0°C isotherm height (4.7 km), high TCLWC (4.0 kg/m2 at 0.01%) and low seasonal cloud base height (356 m).
TL;DR: In this article, the power spectrum density (PSD) and 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 intracontinental earthquakes in Tibet Plateau.
Abstract: 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.
TL;DR: In this article, two E-W trending scarps were identified by aerial photo interpretation and two active normal faults-the Altiprado Faults -were deduced, most of which in historical times, producing 1.38 m and 0.48 m of cumulative displacement.
Abstract: The Azores archipelago is located at the triple junction between the Eurasian, Nubian and North American lithospheric plates, whose boundaries are the Mid-Atlantic Ridge and the Azores-Gibraltar Fault Zone. Sao Miguel is the largest island of the archipelago and is located on the eastern part of the western segment of the Azores-Gibraltar Fault Zone. The Achada das Furnas plateau, located in the central part of the island, between Fogo and Furnas central volcanoes, is dominated by several WNW-ESE and E-W trending alignments of basaltic cinder cones. Two E-W trending scarps were identified by aerial photo interpretation. Transect trenches exposed two active normal faults-the Altiprado Faults ‐ confirming the tectonic nature of the scarps. Several paleoearthquakes were deduced, most of which in historical times, producing 1.38 m and 0.48 m of cumulative displacement. Maximum expected magnitudes (MW) determined from slip per event range from 5.7 to 6.7. One of the events probably corresponds to the historical earthquake of October 22 nd , 1522, the deadliest in the archipelago. Radiocarbon ages are in agreement with this interpretation.
TL;DR: In this paper, a Chirp sub-bottom sonar investigation was performed in the 150 km 2 wideAugustaBasin, located in the eastern Sicily Ionian coast, a region repeatedly hit by strong earthquakes in historical time, with the end of identifying possible evidence of active tectonics.
Abstract: A Chirp sub-bottom sonar investigation was performed in the 150 km 2 wideAugustaBasin, located in the eastern Sicily Ionian coast, a region repeatedly hit by strong earthquakes in historical time, with the end of identifying possible evidence of active tectonics. Seismostratigraphy shows two main reflectors: R1, formed between 60 ka and 19 ka BP, and R2 that is the top of the Holocene deposits. Morphobathymetry reveals two marine abrasion surfaces, Ms1 and Ms2 that are related to the 35 ka and 25 ka BP marine high stills, respectively. This study highlights that R1 and the onlapping Holocene sediments are affected by normal and probably strike-slip faulting. A set of NE-SW striking normal faults represents the oldest system, because they dislocate R1 but not the Holocene deposit. NNW-SSE striking extensional faults show more recent activity since they displace Ms2, the Holocene sequence and cause seafloor up-warping. NE-SW normal faults produce asymmetric basins where the Holocene deposits form wedged bodies. ENE-WSW left-lateral faults dissect a paleo-island, Ms2 and the NNW-SSE fault system. Moreover, seismically induced slumps involving the Holocene sediments, are found at the foot of some fault scarps. The presence of slumped bodies and active faults indicates ongoing deformation in the basin. Identified active faults are consistent with the main regional Malta Escarpment fault system, of which they can be considered as the incipient westernmost extension. This study supports the hypothesis that the Malta Escarpment is active and can be responsible for the regional seismicity.