scholarly journals On the Origin of Orphan Tremors and Intraplate Seismicity in Western Africa

2021 ◽  
Vol 9 ◽  
Author(s):  
T. Olugboji ◽  
Manoochehr Shirzaei ◽  
Yingping Lu ◽  
A. A. Adepelumi ◽  
F. Kolawole
Keyword(s):  
Seismic Station ◽  
Capital City ◽  
Intraplate Seismicity ◽  
Fracture Zones ◽  
Induced Earthquakes ◽  
Tectonic Inheritance ◽  
Western Africa ◽  
Seismic Records ◽  
Shed Light ◽  
Regional Tectonics

On September 5–7, 2018, a series of tremors were reported in Nigeria’s capital city, Abuja. These events followed a growing list of tremors felt in the stable intraplate region, where earthquakes are not expected. Here, we review available seismological, geological, and geodetic data that may shed light on the origin of these tremors. First, we investigate the seismic records for parent location of the orphan tremors using a technique suitable when a single-seismic station is available such as the Western Africa region, which has a sparse seismic network. We find no evidence of the reported tremors within the seismic record of Western Africa. Next, we consider the possibility of a local amplification of earthquakes from regional tectonics, reactivation of local basement fractures by far-field tectonic stresses, post-rift crustal relaxation, landward continuation of oceanic fracture zones, or induced earthquakes triggered by groundwater extraction. Our assessments pose important implications for understanding Western Africa’s intraplate seismicity and its potential connection to tectonic inheritance, active regional tectonics, and anthropogenic stress perturbation.

scholarly journals Indicators for site characterization at seismic station: recommendation from a dedicated survey

2021 ◽  
Author(s):  
Giovanna Cultrera ◽  
Cécile Cornou ◽  
Giuseppe Di Giulio ◽  
Pierre-Yves Bard
Keyword(s):  
Seismic Station ◽  
International Workshop ◽  
Site Characterization ◽  
Companion Paper ◽  
Background Information ◽  
Online Questionnaire ◽  
Seismic Records ◽  
Seismic Networks ◽  
High Level ◽  
Data Acquisition And Processing

AbstractIn recent years, the permanent seismic networks worldwide have largely increased, raising the amount of earthquake signals and the applications using seismic records. Although characterization of the soil properties at recording stations has a large impact on hazard estimates, it has not been implemented so far in a standardized way for reaching high-level metadata. To address this issue, we built an online questionnaire for the identification of the indicators useful for a reliable site characterization at a seismic station. We analysed the answers of a large number of experts in different fields, which allowed us to rank 24 different indicators and to identify the most relevant ones: fundamental frequency (f0), shear-wave velocity profile (VS), time-averaged Vs over 30 m (VS30), depth of seismological and engineering bedrock (Hseis_bed and Heng_bed), surface geology and soil class. Moreover, the questionnaire proposed two additional indices in terms of cost and difficulty to obtain a reliable value of each indicator, showing that the selection of the most relevant indicators results from a complex balance between physical relevancy, average cost and reliability. For each indicator we propose a summary report, provided as editable pdf, containing the background information of data acquisition and processing details, with the aim to homogenize site metadata information at European level and to define the quality of the site characterization (see companion paper Di Giulio et al. 2021). The selected indicators and the summary reports have been shared within European and worldwide scientific community and discussed in a dedicated international workshop. They represent a first attempt to reach a homogeneous set of high-level metadata for site characterization.

scholarly journals SEISMICITY of NORTHERN EURASIA in 2015

2021 ◽  
pp. 10-30
Author(s):  
A. Malovichko ◽  
N. Petrova ◽  
I. Gabsatarova ◽  
R. Mikhailova ◽  
V. Levina ◽  
...  
Keyword(s):  
Seismic Station ◽  
Seismic Energy ◽  
Annual Number ◽  
Northern Eurasia ◽  
Middle Urals ◽  
Induced Earthquakes ◽  
Seismic Regime ◽  
East European ◽  
Tectonic Earthquakes ◽  
Seismic Networks

The review of the Northern Eurasia seismicity for 2015 includes a description of seismic networks, the results of analysis of the seismic regime and individual noticeable earthquakes in 16 regions of Russia and neighbouring countries. Seismic monitoring was carried out by the networks of seismic station of Russia, Azerbaijan, Armenia, Belarus, Kazakhstan, Kyrgyzstan, Latvia, Moldova, Turkmenistan, Tajikistan, Uzbekistan, Ukraine, including 599 digital, 7 analogue stations and eight seismic groups. In 2015, these networks registered about 27 thousand tectonic earthquakes, over 6 thousand volcanic earthquakes, 599 explosions, 23 mountain-tectonic shocks and induced earthquakes. Focal mechanisms of 592 earthquakes were determined, the information on manifestations of 449 perceptible earthquakes was collected. 26 shocks were felt in settlements of Northern Eurasia with an intensity Ii≥5. According to estimates of the annual number and released seismic energy in 2015 in comparison with the long-term characteristics of the seismic regime, the seismic process in most regions of Northern Eurasia proceeded in the “background” regime. An exception is Tajikistan and adjacent territories, where two strong earthquakes occurred – the Hindu Kush earthquake on October 26 with Mw=7.5, h=230 km in northern Afghanistan, near the border with Tajikistan, and the Sarez earthquake on December 7 with Mw=7.2, Ms=7.6, h=20 km in Tajikistan. Both earthquakes were accompanied by numerous aftershocks and were felt in Tajikistan with intensities Imax=7 and Imax=7–8 respectively, on the MSK-64 scale. Notable event on the territory of Northern Eurasia in 2015 is the emergence of the Muyakan sequence of earthquakes, the largest for the period of instrumental observations in the region "Baikal and Transbaikalia", as a result of which the number of recorded earthquakes in the region quadrupled concerning 2014. The other interesting fact is occurrence of tangible earthquakes in the regions, traditionally considered weakly seismic – near the Semipalatinsk test area in Eastern Kazakhstan (Chingiz earthquake on January 20, Ms=4.1, I0=5–6), in the Middle Urals (Middle Ural earthquake on October 18 with ML=4.7, I0=6) and in the southwest of East -European platform (Poltava earthquake on February 3 with KR=10.7, I0=6).

An analysis of the hospitals of Sultan Suleyman and Hurrem: Two different approaches to healthcare in sixteenth-century Ottoman Empire

2017 ◽  
Vol 27 (2) ◽  
pp. 102-108
Author(s):  
Pinar Kayaalp
Keyword(s):  
Public Health ◽  
Sixteenth Century ◽  
Ottoman Empire ◽  
Capital City ◽  
Ruling Class ◽  
Modus Operandi ◽  
Dual Approach ◽  
Gender Specific ◽  
Shed Light

This study concentrates on two monumental Ottoman pious endowments, each with a major component devoted to healing. The first is the hospital of the Haseki Mosque Complex built by the wife of Sultan Suleyman the Magnificent. An examination of the deed and the modus operandi of this endowment will impart a sense of the role that women of the ruling class played in Ottoman society as builders and healers in the sixteenth century. The analysis of the Haseki Hospital will be followed by an examination of the hospital that is part of the Suleymaniye Mosque Complex built by Sultan Suleyman. The differences between the two perspectives in the promotion of public health will be emphasized, arguing that the Sultan’s approach to healthcare was academic and research-oriented, whereas his wife’s was holistic and devoted to rehabilitation. The endowment deeds and the physical layouts of the two hospitals shed light upon a dual approach to healthcare with gender-specific roles affirmed and shaped by Hurrem and Suleyman the Magnificent, who each built hospitals of their own in Istanbul, the Ottoman capital city.

scholarly journals Técnicas de Geoprocessamento Aplicada à Análise de Padrões Pontuais como uma Contribuição a Cartografia de Zonas Sísmicas no estado de Goiás

2016 ◽  
Vol 10 (2) ◽  
pp. 128
Author(s):  
Alexandre Henrique Cardoso Do Vale e Silva ◽  
Fabrizia Gioppo Nunes
Keyword(s):  
Information System ◽  
Structural Geology ◽  
Spatial Arrangement ◽  
Intraplate Seismicity ◽  
Point Patterns ◽  
The North ◽  
Intraplate Tectonics ◽  
The World ◽  
Système D’Information ◽  
Seismic Records

Resumo Eventos sísmicos estão em todo mundo, inclusive no Brasil. No Estado de Goiás, este fenômeno pode ser observado em determinadas regiões. O estudo sismológico é complexo, e se torna ainda mais, quando referente à tectônica intraplaca. O uso de técnicas de geoprocessamento, bem como da aplicação metodológica da análise espacial para o tratamento de registros sísmicos, podem contribuir para a interpretação destes eventos. Pretende-se aqui, entender os padrões pontuais na identificação de áreas de clusters de epicentros, representados em produtos cartográficos. A organização das informações de ocorrências sísmicas em ambientes de Sistema de Informação Geográfica colabora na análise dos fatos relacionados aos abalos tectônicos e de sua dinâmica, promovendo um diagnóstico para o zoneamento do potencial sismológico da região de estudo. Após análise dos mapas gerados em associação com a geologia estrutural e a geofísica, pode-se observar um aglomerado pertinente aos municípios das mesorregiões norte e noroeste do Estado.Palavras-chave: Geotecnologia. Cartografia. Arranjo Espacial. Sismicidade Intraplaca. AbstractSeismic events are around the world, including Brazil. In the State of Goiás, this phenomenon can be observed in certain regions. The seismological study is complex, and it becomes even more so when referring to intraplate tectonics. The use of geoprocessing techniques, as well as the methodological application of spatial analysis for the treatment of seismic records, can contribute to the interpretation of these events. It is intended here, to understand the point patterns in identifying areas of clustering of epicenters, represented in cartographic products. The organization of seismic occurrence information on geographic information system environments collaborate on the analysis of facts related to tectonic quakes and its dynamics, promoting a diagnosis for the zoning of the seismological potential of the region studied. After analyzing the maps generated in association with structural geology and geophysics, one can observe a cluster relevant to the municipalities of the north and northwest mesoregions of the state.Keywords: Geotechnology. Cartography. Spatial Arrangement. Intraplate Seismicity. RésuméÉvénements sismiques sont partout dans le monde, y compris le Brésil. Dans l'État de Goiás, ce phénomène peut être observé dans certaines régions. L'étude sismologique est complexe, et devient encore plus lorsqu'on se réfère à la tectonique intraplaque. L'utilisation de techniques de géotraitement, ainsi que l'application méthodologique de l'analyse spatiale pour le traitement des enregistrements sismiques, peuvent contribuer à l'interprétation des événements. Il est prévu ici, comprendre les standards ponctuels dans l'identification des domaines des clusters d’épicentres, représentés dans les produits cartographiques. L'organisation des informations d'événements sismiques dans les environnements de système d'information géographique collabore sur l'analyse des faits liés aux tremblements de terre tectoniques et sa dynamique, en promouvant un diagnostic pour le zonage du potentiel sismique de la région d'étude. Après avoir analysé les cartes générées en association avec la géologie structurale et de la géophysique, on peut observer un cluster pertinente pour les municipalités des mésorégions du nord et du nord-ouest de l'État.Mots-clés: Géotechnique. Cartographie. Arrangements Spatiaux. Sismicité Intraplaque.

scholarly journals Contribution of calving to frontal ablation quantified from seismic and hydroacoustic observations calibrated with lidar volume measurements

2019 ◽  
Author(s):  
Andreas Köhler ◽  
Michał Pętlicki ◽  
Pierre-Marie Lefeuvre ◽  
Giuseppa Buscaino ◽  
Christopher Nuth ◽  
...  
Keyword(s):  
Temporal Resolution ◽  
Seismic Station ◽  
Time Lapse ◽  
High Temporal Resolution ◽  
Tidewater Glaciers ◽  
Relative Contribution ◽  
Glacier Front ◽  
Volume Measurements ◽  
Seismic Records ◽  
Frontal Ablation

Abstract. Frontal ablation contributes significantly to the mass balance of tidewater glaciers in Svalbard and can be recovered with high temporal resolution using continuous seismic records. Determination of the relative contribution of dynamic ice loss through calving to frontal ablation requires precise estimates of calving volumes at the same temporal resolution. We combine seismic and hydroacoustic observations close to the calving front of Kronebreen, a marine terminating glacier in Svalbard, with repeat lidar scanning of the glacier front. Simultaneous time-lapse photography is used to assign volumes measured from lidar scans to seismically detected calving events. Empirical models derived from signal properties such as integrated amplitude are able to replicate volumes of individual calving events and cumulative subaerial ice loss over different lidar scan intervals from seismic and hydroacoustic data alone. This enables quantification of the contribution of calving to frontal ablation, which we estimate for Kronebreen to be about 18–30 %, slightly below the subaerially exposed area of the glacier front. We further develop a model calibrated for the permanent seismic station KBS at about 15 km distance from the glacier front, where 15–60 % of calving events can be detected under variable noise conditions due to reduced signal amplitudes at distance. Between 2007 and 2017, we find a 5–30 % contribution of calving ice blocks to frontal ablation which emphasizes the importance of underwater melting (roughly 150–350 m a−1). This study shows the feasibility to seismically monitor not only frontal ablation rates but also its dynamic ice loss contribution continuously and at high temporal resolution.

Locating the rock hazard and understanding its physical process using seismic signals

2020 ◽  
Author(s):  
Jui-Ming Chang ◽  
Wei-An Chao ◽  
Hongey Chen
Keyword(s):  
Physical Process ◽  
Epicentral Distance ◽  
Seismic Station ◽  
Regional Scale ◽  
Seismic Signals ◽  
Fractured Bedrock ◽  
Event Location ◽  
Movement Type ◽  
Seismic Records ◽  
The Government

<p>Rock hazard is a common geohazard event that occurs in the orogenic mountain belt and often causes the destruction of road and casualties. The steep topography, fractured bedrock and frequent earthquakes favor to happen. Those are usually fast and unpredictable, leading a lack of direct observation of physical process. Recent seismological studies highlighted the rock hazard induced seismic signals could improve understanding of its dynamics. This study focuses on the three provincial highways that cross the Taiwan Island from east to west. The regions along the highways have the complexity in tectonic structure and extreme climate-forced erosion, causing the hazard frequently occurred. In order to understanding seismic features and physical process of rock hazard, we conducted a series of seismic analyses using the seismic records collected form regional seismic network for ten events, which were reported by the government agency. Four of them have the video recordings, which would be helpful to understanding the relationships between physical process (falling, rolling, bouncing and fragmentation), movement type (fall, topple, slump, slide, avalanche or complex) and seismic features. We developed the hybrid method of determination of geohazard event location (GeoLoc) that combines the cross-correlation-based method and the amplitude-attenuation-based approach. We apply the GeoLoc scheme to locate the events recorded by the seismic station with epicentral distance ranging from 2 to 56 kilometers (km) and it helps to reduce the location error. The leading seismic signals of the mass detachment linked to the crack propagation or slope response can be observed, and we also found that the seismic feature caused by fragment of rock block exhibits the higher frequency than the seismic signals corresponding to impaction of rock particles. Our results highlight the possibility of the seismic technique for locating rock hazards distributed along highways in a regional scale and further understanding its physical process. The aforementioned results would be helpful to build the near-real-time monitoring system along the highways for hazard mitigation of events.</p>

scholarly journals Dynamic Characteristics of a Tall Building Identified from Earthquake and Ambient Vibration Records

2015 ◽  
Vol 11 (4) ◽  
pp. 1-9
Author(s):  
Cristian Andone ◽  
Sorin Demetriu ◽  
Alexandru Aldea
Keyword(s):  
Dynamic Characteristics ◽  
Seismic Station ◽  
Shear Wall ◽  
Tall Building ◽  
Ambient Vibration ◽  
Reinforced Concrete Structure ◽  
The Third ◽  
Acceleration Sensors ◽  
Seismic Records ◽  
Seismic Instrumentation

Abstract The paper presents the modal characteristics of a tall building in Bucharest (BRD-SG Tower) identified from earthquake and ambient vibration records. The building was built in the early 2000’s and has a reinforced concrete structure (inner shear wall tube and perimeter frames) with 3 underground stories, ground floor and 18 stories. The seismic instrumentation of the building consists of a seismic station with two triaxial acceleration sensors located at the top of the building (+69.6 m) and at the third basement (−9.3 m). The dynamic characteristics of the building are estimated from the seismic records from 23 earthquakes (with moment magnitudes MW between 3.7 and 6.0) that occurred during the period 2004÷2010. The results obtained from the earthquake records are compared with those obtained from 35 ambient vibration records from the period 2003 ÷ 2010.

scholarly journals On the Origin of Orphan Tremors & Intraplate Seismicity in Western Africa

2021 ◽  
Author(s):  
Tolulope Morayo Olugboji ◽  
Manoochehr Shirzaei ◽  
Yingping Lu ◽  
Adekunle Abraham Adepelumi ◽  
Folarin Kolawole
Keyword(s):  
Intraplate Seismicity ◽  
Western Africa

scholarly journals A study of local site effects in Benevento(Southern Italy) by the analysis of seismic records of explosions

1995 ◽  
Vol 38 (3-4) ◽  
Author(s):  
G. Iannaccone ◽  
L. Improta ◽  
G. Biella ◽  
M. Castellano ◽  
A. Deschamps ◽  
...  
Keyword(s):  
Ground Motion ◽  
Seismic Station ◽  
Spectral Ratio ◽  
Seismic Signal ◽  
Middle Pleistocene ◽  
Natural Period ◽  
Alluvial Deposits ◽  
Average Spectrum ◽  
Seismic Records ◽  
The Town

In this paper we evalllate the seismic amplification effects in the town of Benevento llsing records of an explo- sion of 500 kg fired at abollt 7 km. Seismic records were obtained at 43 selected sites in the city by digital three-component stations. A data selection performed on the signal-to-noise ratio reduced the available data to 26 stations. We used the spectral ratio techniques to evaluate the amplification effects of each recording site compared both to the average spectrum calculated over 26 stations and to a reference seismic station. The shapes of the spectral ratios were classified according to the geological characteristics of the site. A characteristic shape of the spectral ratio was observed to be related to the specific structure of the subsoil. In particular, the sites on basin sediments (Lagonegro Unit) and Middle Pleistocene conglomerates failed to show amplification effects; the sites on thick alluvial deposits showed amplification in the 5-9 Hz range; finally, sites on alluvial-lacustrine deposits amplified the seismic signal at frequencies depending on the characteristics and the thickness of the deposit. In addition, damage distribution caused by the 1688 earthquake in Benevento was related to the thickness of the surface layers in the ancient built-up area of the town. The study of the spectral ra- tios showed that these deposits amplify ground motion at frequencies between 9 and 12 Hz, i.e. frequencies close to the natural period of the most widespread buildings at that time in Benevento. Geological and seismic data were jointly used to carry out a zonation of the urban area of Benevento on the basis of homogeneous seismic responses. The validity of this analysis is limited to the main frequency band and amplitude of ground motion produced by the explosions.

scholarly journals The Impact Of Location On The Role Of Small Towns In Regional Development: Mazovia, Poland

2016 ◽  
Vol 8 (4) ◽  
pp. 413-426 ◽  
Author(s):  
Konrad Czapiewski ◽  
Jerzy Bański ◽  
Magdalena Górczyńska
Keyword(s):  
Rural Areas ◽  
Small Towns ◽  
Capital City ◽  
Population Concentration ◽  
Local Labour ◽  
Zone Of Influence ◽  
Surrounding Areas ◽  
The Impact ◽  
Shed Light

Abstract The paper explores the role of small towns in the Mazovia region in Poland which is both characterized by rural areas and the suburban zone of Warsaw. The analysis of changes in the local labour markets reveals that microregions formed by small peripheral towns were more resistant to changes than those located in the suburban area of Warsaw. The latter were absorbed by the capital city whose zone of influence expanded in the detriment of adjacent small towns and their microregions. Using the concept of exogenous functions performed by small towns, we also shed light on their role with regard to the surrounding areas (with dominant agricultural function) in the past decade. The values of the service concentration index (SCI) and the level of population concentration showed that the majority of services to local and neighbouring inhabitants were delivered in small county towns located in the periphery. On the other hand, small county towns located in the vicinity of Warsaw mainly provided services to their inhabitants.

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