scholarly journals "Real time analysis" of the ion density measured by the satellite DEMETER in relation with the seismic activity

2012 ◽  
Vol 12 (9) ◽  
pp. 2957-2963 ◽  
Author(s):  
M. Li ◽  
M. Parrot
Keyword(s):  
Seismic Activity ◽  
False Alarms ◽  
Seismic Zone ◽  
Data Set ◽  
Ion Density ◽  
Real Time Analysis ◽  
Number Of False Alarms ◽  
Future Earthquake ◽  
Automatic Search ◽  
Seismic Area

Abstract. This paper is related to the study of the ion density recorded by the low altitude satellite DEMETER. In a first time there is an automatic search for ionospheric perturbations in the complete satellite data set of ion densities. Then perturbations due to known ionospheric phenomena (for example, solar activity) are eliminated as well as perturbations not above a seismic zone. In a second time, there is a search to know if each selected perturbation corresponds to a future earthquake. The earthquakes have been classified depending on their magnitude and depth. This attempt to predict earthquakes of course generates false alarms and wrong detections. The results of this statistical analysis are presented as function of various parameters. It is shown that the number of false alarms is very important, because the ionosphere has variations not only linked to the seismic activity. The number of wrong detections is also important and can be explained by the fact that the satellite is above a seismic area only a few minutes per day and we do not expect continuous perturbations from a given earthquake. The more important results of this study is that the ratio between detected earthquakes and earthquakes to be detected increases with the magnitude of the earthquakes which intuitively makes sense.

Seismic activity and structural features in the Charlevoix region, Quebec

1987 ◽  
Vol 24 (11) ◽  
pp. 2118-2129 ◽  
Author(s):  
Maurice Lamontagne
Keyword(s):  
Seismic Activity ◽  
Impact Crater ◽  
Time Window ◽  
Fault System ◽  
Earthquake Risk ◽  
Earthquake Activity ◽  
Seismic Zone ◽  
Nodal Solutions ◽  
Data Set ◽  
The Impact

The Charlevoix region is historically the most active earthquake zone in eastern Canada. Understanding the links between its seismicity and the faults of the region is important for the assessment of earthquake risk along the St. Lawrence Valley. The region has been monitored by a microseismic array since 1977, yielding accurate locations of the hypocentres. Previous analyses of data from the array indicated a relationship between the earthquakes and the St. Lawrence Valley paleorift faults. As a sequel to previous studies, the relationships between the seismic activity and the faults of the region were reexamined through the use of the composite P-nodal solutions, in an effort to clarify the nature of faulting in the seismic zone. The microseisms were partitioned into subsets of events on the basis of geological and hypocentre-trend considerations. The main objectives of this paper are to delineate the details of faulting within the Charlevoix region and to determine the effect of the impact crater on the nature of faulting in this area.Assuming a constant 6.2 km/s velocity model and using a data set of 107 events, composite fault-plane solutions were computed. The composite P-nodal solutions indicated that the Charlevoix impact crater modifies to a certain extent the focal-mechanism characteristics. Events outside the impact crater were found to be quite consistent in their polarity distribution on the focal sphere, suggesting similarity in their focal mechanisms. The composite mechanism of these events suggests a relationship between the earthquakes and the north–south faults mapped outside the impact crater. The magnitude mb (Lg) 5.0 earthquake of August 19, 1979, the largest event in the selected time window, had different fault planes than some of its aftershocks. Nevertheless, the polarity distribution of the aftershocks was in agreement with the average trend for the events outside the crater. Events inside the impact crater were found to be produced along more variable fault orientations, with an average trend similar to that of the rift fault system. It is proposed that the meteor impact weakened the rift faults and introduced its own fractures. The present earthquake activity probably occurs along these weak fault surfaces. The effect of the impact crater on the type of faulting versus depth is not readily discernible from available data. In general, meteor impacts do not leave neotectonic seismic signatures: the Charlevoix impact crater might represent a different case because of the presence of weakened paleorift faults.

scholarly journals A Data-Driven Surrogate Approach for the Temporal Stability Forecasting of Vegetation Covered Dikes

Water ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 107
Author(s):  
Elahe Jamalinia ◽  
Faraz S. Tehrani ◽  
Susan C. Steele-Dunne ◽  
Philip J. Vardon
Keyword(s):  
Numerical Simulation ◽  
Water Flux ◽  
Temporal Stability ◽  
Synthetic Data ◽  
Climatic Conditions ◽  
Training Data ◽  
Data Driven ◽  
Data Set ◽  
Surface Cracking ◽  
Real Time Analysis

Climatic conditions and vegetation cover influence water flux in a dike, and potentially the dike stability. A comprehensive numerical simulation is computationally too expensive to be used for the near real-time analysis of a dike network. Therefore, this study investigates a random forest (RF) regressor to build a data-driven surrogate for a numerical model to forecast the temporal macro-stability of dikes. To that end, daily inputs and outputs of a ten-year coupled numerical simulation of an idealised dike (2009–2019) are used to create a synthetic data set, comprising features that can be observed from a dike surface, with the calculated factor of safety (FoS) as the target variable. The data set before 2018 is split into training and testing sets to build and train the RF. The predicted FoS is strongly correlated with the numerical FoS for data that belong to the test set (before 2018). However, the trained model shows lower performance for data in the evaluation set (after 2018) if further surface cracking occurs. This proof-of-concept shows that a data-driven surrogate can be used to determine dike stability for conditions similar to the training data, which could be used to identify vulnerable locations in a dike network for further examination.

Algorithms for detecting broadband signals with a constant level of false alarms

2021 ◽  
Author(s):  
I.F. Lozovskiy
Keyword(s):  
Detection Threshold ◽  
Signal Amplitude ◽  
Rayleigh Distribution ◽  
Training Sample ◽  
Detection Algorithm ◽  
Constant Level ◽  
False Alarms ◽  
Interference Power ◽  
Number Of False Alarms ◽  
Distribution Type

The use of broadband souding signals in radars, which has become real in recent years, leads to a significant reduction in the size of resolution elements in range and, accordingly, in the size of the window in which the training sample is formed, which is used to adapt the detection threshold in signal detection algorithms with a constant level of false alarms. In existing radars, such a window would lead to huge losses. The purpose of the work was to study the most rational options for constructing detectors with a constant level of false alarms in radars with broadband sounding signals. The problem was solved for the Rayleigh distribution of the envelope of the noise and a number of non-Rayleigh laws — Weibull and the lognormal, the appearance of which is associated with a decrease in the number of reflecting elements in the resolution volume. For Rayleigh interference, an algorithm is proposed with a multi-channel in range incoherent signal amplitude storage and normalization to the larger of the two estimates of the interference power in the range segments. The detection threshold in it adapts not only to the interference power, but also to the magnitude of the «power jump» in range, which allows reducing the number of false alarms during sudden changes in the interference power – the increase in the probability of false alarms did not exceed one order of magnitude. In this algorithm, there is a certain increase in losses associated with incoherent accumulation of signals reflected from target elements, and losses can be reduced by certain increasing the size of the distance segments that make up the window. Algorithms for detecting broadband signals against interference with non-Rayleigh laws of distribution of the envelope – Weibull and lognormal, based on the addition of the algorithm for detecting signals by non-linear transformation of sample counts into counts with a Rayleigh distribution, are studied. The structure of the detection algorithm remains unchanged in practice. The options for detectors of narrowband and broadband signals are considered. It was found that, in contrast to algorithms designed for the Rayleigh distribution, these algorithms provide a stable level of false alarms regardless of the values of the parameters of non-Rayleigh interference. To reduce losses due to interference with the distribution of amplitudes according to the Rayleigh law, detectors consisting of two channels are used, in which one of the channels is tuned for interference with the Rayleigh distribution, and the other for lognormal or Weibull interference. Channels are switched according to special distribution type recognition algorithms. In such detectors, however, there is a certain increase in the probability of false alarms in a rather narrow range of non-Rayleigh interference parameters, where their distribution approaches the Rayleigh distribution. It is shown that when using broadband signals, there is a noticeable decrease in detection losses in non-Rayleigh noise due to lower detection thresholds for in range signal amplitudes incoherent storage.

An Automated Conflict-alert Function for an Air Traffic Control System

1980 ◽  
Vol 33 (3) ◽  
pp. 475-481
Author(s):  
P. Bertolazzi ◽  
M. Lucertini
Keyword(s):  
Decision Making ◽  
Control System ◽  
Traffic Control ◽  
Air Traffic Control ◽  
Air Traffic ◽  
False Alarms ◽  
Major Purpose ◽  
Number Of False Alarms ◽  
Traffic Control System

The major purpose of an air traffic control system is to ensure the separation of two or more aircraft flying in the same airspace, with an efficiency that can be expressed in terms of capacity and cost. As air traffic grows in numbers it becomes necessary to reduce the workload of the controllers by relieving them of many monitoring tasks, and eventually some decision-making tasks, through computerized automation. In this context many developments tend to build up an efficient conflict-alert subsystem.The problem of conflict-alert in the air needs strategic tools, to make collision unlikely or even impossible, and tactical tools to detect impending collisions. The latter detect potentially hazardous aircraft encounters and alert the controller in time to warn the pilots (if necessary) and should obviously provide this capability with a minimal number of false alarms and no increase in workload.

scholarly journals Analysis of soil radon data in earthquake precursory studies

2014 ◽  
Vol 57 (5) ◽  
Author(s):  
Hari Prasad Jaishi ◽  
Sanjay Singh ◽  
Raghavendra Prasad Tiwari ◽  
Ramesh Chandra Tiwari
Keyword(s):  
Statistical Analysis ◽  
Multiple Regression ◽  
Radon Concentration ◽  
Seismic Activity ◽  
Meteorological Parameters ◽  
Regression Method ◽  
Seismic Zone ◽  
Type Ii ◽  
Soil Radon ◽  
Multiple Regression Method

<p>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.</p>

scholarly journals Classification Connection of Twitter Data using K-Means Clustering

2019 ◽  
Vol 8 (6S4) ◽  
pp. 14-22
Keyword(s):  
Social Media ◽  
Real Time ◽  
Clustering Methods ◽  
Time Analysis ◽  
Data Set ◽  
Dynamic Data ◽  
Real Time Analysis ◽  
Twitter Data ◽  
Social Media Platforms ◽  
Insight Into

The rise of social media platforms like Twitter and the increasing adoption by people in order to stay connected provide a large source of data to perform analysis based on the various trends, events and even various personalities. Such analysis also provides insight into a person’s likes and inclinations in real time independent of the data size. Several techniques have been created to retrieve such data however the most efficient technique is clustering. This paper provides an overview of the algorithms of the various clustering methods as well as looking at their efficiency in determining trending information. The clustered data may be further classified by topics for real time analysis on a large dynamic data set. In this paper, data classification is performed and analyzed for flaws followed by another classification on the same data set.

scholarly journals Structural Design of Skyscrapers Susceptible to Seismic Activity and Soil Liquefaction

2020 ◽  
Vol 8 (5) ◽  
pp. 2546-2554
Keyword(s):  
Structural Design ◽  
Seismic Activity ◽  
Soil Liquefaction ◽  
Andaman Sea ◽  
Seismic Loads ◽  
Seismic Zone ◽  
Safety Measures ◽  
High Rise ◽  
Ground Condition ◽  
High Chance

The design of skyscrapers involves lot of aspects such as the building must withstand heavy dead loads, should have safety measures against fire, floors must be easily accessible, and should have resistant against wind and seismic loads that can be detrimental to the safety of the skyscraper. Pile foundations are usually adopted for high rise buildings and when it is combined with raft slab they ensure that the problems of differential settlement are taken care of. In this paper the scenario of designing a skyscraper in seismic zone that is prone to earthquakes and the ground condition is such that it is located in vicinity of sea. Andaman and Nicobar isle is one similar place it falls under Zone V as per Indian Standards, hence prone to seismic activity and since it is surrounded by Bay of Bengal and Andaman sea, when seismic activity occurs there is a high chance of soil liquefaction to occur hence proper structural designs should be embraced.

scholarly journals Coupling ensemble weather predictions based on TIGGE database with Grid-Xinanjiang model for flood forecast

2011 ◽  
Vol 29 ◽  
pp. 61-67 ◽  
Author(s):  
H.-J. Bao ◽  
L.-N. Zhao ◽  
Y. He ◽  
Z.-J. Li ◽  
F. Wetterhall ◽  
...  
Keyword(s):  
Weather Prediction ◽  
Grid Cell ◽  
Flood Forecasting ◽  
False Alarms ◽  
Flood Forecast ◽  
Distributed Hydrological Model ◽  
Xinanjiang Model ◽  
Numerical Weather ◽  
Number Of False Alarms ◽  
Promising Tool

Abstract. The incorporation of numerical weather predictions (NWP) into a flood forecasting system can increase forecast lead times from a few hours to a few days. A single NWP forecast from a single forecast centre, however, is insufficient as it involves considerable non-predictable uncertainties and lead to a high number of false alarms. The availability of global ensemble numerical weather prediction systems through the THORPEX Interactive Grand Global Ensemble' (TIGGE) offers a new opportunity for flood forecast. The Grid-Xinanjiang distributed hydrological model, which is based on the Xinanjiang model theory and the topographical information of each grid cell extracted from the Digital Elevation Model (DEM), is coupled with ensemble weather predictions based on the TIGGE database (CMC, CMA, ECWMF, UKMO, NCEP) for flood forecast. This paper presents a case study using the coupled flood forecasting model on the Xixian catchment (a drainage area of 8826 km2) located in Henan province, China. A probabilistic discharge is provided as the end product of flood forecast. Results show that the association of the Grid-Xinanjiang model and the TIGGE database gives a promising tool for an early warning of flood events several days ahead.

Imaging the Active Faults of the Central New Madrid Seismic Zone Using Panda Array Data

1992 ◽  
Vol 63 (3) ◽  
pp. 375-393 ◽  
Author(s):  
J.M. Chiu ◽  
A.C. Johnston ◽  
Y.T. Yang
Keyword(s):  
Hanging Wall ◽  
Active Faults ◽  
Velocity Model ◽  
New Madrid Seismic Zone ◽  
Seismic Zone ◽  
Thrust Faults ◽  
Secondary Phases ◽  
Low Velocity ◽  
Data Set ◽  
New Madrid

Abstract More than 700 earthquakes have been located in the central New Madrid seismic zone during a two-year deployment of the PANDA array. Magnitudes range from < 0.0 to the mblg 4.6 Risco, Missouri earthquake of 4 May 1991. The entire data set is digital, three-component and on-scale. These data were inverted to obtain a new shallow crustal velocity model of the upper Mississippi embayment for both P- and S-waves. Initially, inversion convergence was hindered by extreme velocity contrasts between the soft, low-velocity surficial alluvial sediments and the underlying Paleozoic carbonate and clastic high-velocity rock. However, constraints from extensive well log data for the embayment, secondary phases (Sp and Ps), and abundant, high-quality shear-wave data have yielded a relatively robust inversion. This in turn has led to a hypocentral data set of unprecedented quality for the central New Madrid seismic zone. Contrary to previous studies that utilized more restricted data, the PANDA data clearly delineate planar concentrations of hypocenters that compel an interpretation as active faults. Our results corroborate the vertical (strike-slip) faulting of the the southwest (axial), north-northeast, and western arms and define two new dipping planes in the central segment. The seismicity of the left-step zone between the NE-trending vertical segments is concentrated about a plane that dips at ∼31°SW; a separate zone to the SE of the axial zone defines a plane that dips at ∼48°SW. The reason for this difference in dip, possibly defining segmentation of an active fault, is not dear. When these planes are projected up dip, they intersect the surface along the eastern boundary of the Lake County uplift (LCU) and the western portion of Reelfoot Lake. If these SW-dipping planes are thrust faults, then the LCU would be on the upthrown hanging wall and Reelfoot Lake on the downthrown footwall. If in turn these inferred thrust faults were involved in the 1811–12 and/or pre-1811 large earthquakes, they provide an internally consistent explanation for (1) the existence and location of the LCU, (2) the wide-to-the-north, narrow-to-the-south shape of the LCU, and (3) the subsidence and/or impoundment of Reelfoot Lake.

scholarly journals Determination of level and time thresholds for detectors with normalized indicator process

2020 ◽  
Author(s):  
С.Б. Егоров ◽  
Р.И. Горбачев
Keyword(s):  
False Alarm ◽  
Average Rate ◽  
Probability Model ◽  
False Alarm Probability ◽  
Statistical Characteristics ◽  
False Alarms ◽  
Time Interval ◽  
Number Of False Alarms ◽  
Time Threshold ◽  
Selection Threshold

«Выбросовая» вероятностная модель работы обнаружителя в режиме ожидания сигнала, предложенная авторами в [1], использована для оценки влияния селекции выбросов по длительности на вероятность ложной тревоги. Флюктуационные выбросы помехового индикаторного процесса, превысившие пороги селекции по уровню и длительности, трактуются как редкие события на интервале ожидания сигнала, подчиняющиеся вероятностному закону Пуассона. При условии, что средний период следования ложных выбросов превышает интервал корреляции индикаторного процесса, получено соотношение между средним числом выбросов любой длительности и средним числом выбросов, превысивших пороговую длительность. На основании известных числовых и вероятностных характеристик выбросов нормального стационарного случайного процесса получен уравнения, связывающие относительные пороги селекции по уровню и длительности с вероятностью ложной тревоги на интервале ожидания сигнала. Предложена методика определения порога селекции по длительности для снижения порога селекции по уровню до заданной величины. «Emissional» probability model of the detector in stand-by mode proposed by the authors in [1], is intended for estimation of false alarm rate dependence from the value of time-selection threshold. Fluctuation emissions of the noise indicator process are interpreted as rare events correspond to Poisson distribution. Assuming that average rate of false alarms exceeds the correlation interval of indicator process, obtained equation between average number of false alarms of any duration and average number of false alarms exceed the time threshold. Based on known numerical and statistical characteristics of emissions of normal stationary random process obtained equations, relating time and level thresholds with false alarm probability on stand-by mode time interval. Also suggested a method of determining time threshold intended to reduce level threshold.

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