The reliability of North American seismological stations

1957 ◽  
Vol 47 (1) ◽  
pp. 1-5
Author(s):  
Eugene Herrin
Keyword(s):  
Standard Deviation ◽  
North American ◽  
Systematic Difference ◽  
Travel Times ◽  
Seismic Stations

Abstract Estimates are given for the reliabilities of fifty-eight North American seismic stations, based on I.S.S. P-time residuals of Mexican earthquakes for 1941, 1942, 1943, and 1944. The ten most reliable stations were found to be Tinemaha, Riverside, Pasadena, Mount Wilson, Tucson, Lick, Weston, Palomar, Haiwee, and Seven Falls. The standard deviation of a single P arrival for the more reliable stations is ± 2.0 seconds or greater. A systematic difference in travel times between the California stations and eastern stations, and particularly between Ottawa and the Pasadena group, is strongly suggested. P arrivals at Ottawa are about one second faster than for the Pasadena group.

EVALUATION OF THE SKELETAL AGE METHOD OF ESTIMATING CHILDREN'S DEVELOPMENT

PEDIATRICS ◽  
1954 ◽  
Vol 13 (2) ◽  
pp. 165-173
Author(s):  
DONALD MAINLAND
Keyword(s):  
Standard Deviation ◽  
Assessment Method ◽  
Systematic Difference ◽  
Skeletal Age ◽  
Nutrition Survey ◽  
Quick Method ◽  
Age Assessment ◽  
Variable Error ◽  
Significant Difference ◽  
The Individual

An observer's variable error in skeletal age assessment of hand RGs (i.e., the irregular ion between independent readings of the same film) was studied on 1,124 readings of 326 films from 233 children aged 16 months to 17 years. seventy-nine of the RGs were full-size reproductions in Macyr's Nutrition and Chemical Growth in Childhood; the remainder were actual films of children in Halifax, Canada (healthy Orphanage residents and children examined in a nutrition survey). There was no significant difference in variable error associated with the atlas (Todd, Greulich-Pyle), age of child, sex, differences between skeletal and chronologic age, differences between children, or differences between RGs of the same child, except for a tendency in the Macy Series for the poorest reproductions to have a larger variable error than the best reproductions. ions. In most readings the individual indicators were assessed separately and the results averaged, but a quicker method (over-all appraisal) did not produce a significantly different variable error. The quick method may be useful in large surveys, although it appears too coarse for the study of individual children. The observer's variable error was expressed by standard deviations of approximately three months (Macy Series—both atlases; Nutritirn Series—Greulich-Pyle atlas) and four months (Orphanage Series—both atlases). With a standard deviation of three months an assessor must affix an error of ± 8.3 months to his estimate of a child's progress in skeletal age, in order to obtain confidence limits with 95% probability. If his standard deviation is four months he must allow ± 11.1 months. For evaluation of the assessment method, many observers' estimates of variable error are needed, and an appeal for data is issued. After more than 1200 readings had been made the observer's practice lapsed for about a year. Reassessment of a random sample of RGs then showed, besides variable error, a mean systematic difference of approximately three months from the previous readings of the same films with the same atlas. To avoid this risk, any two films that are to be assessed for skeletal progress should be read within a few weeks of each other, and special precautions are therefore necessary to secure independence of the two readings.

On Pulses whose Travel Times are not True Minima

1943 ◽  
Vol 39 (1) ◽  
pp. 48-51 ◽  
Author(s):  
Harold Jeffreys
Keyword(s):  
Standard Deviation ◽  
Maximum Frequency ◽  
Travel Times ◽  
Stationary Time ◽  
The Times

In the construction of the seismological tables it has been found that the times of several pulses at a given distance show a well-marked maximum frequency for each, about which the bulk of the observations are spread with a standard deviation of 1·5−3 sec. For others there was only a vague concentration, spread over about half a minute (Jeffreys and Bullen, 1936–40). The theoretical times of the latter type could all be calculated from those of the former by using the principle of stationary time for small variations of the path, and the observed times might be either shorter or longer than the theoretical ones. There was a complete association between the type of distribution of the residuals and the nature of the path. Whenever the time as calculated was a minimum for all small variations of the path, the distribution of residuals was of the former type; when it was stationary without being either a true minimum or a maximum it was of the latter.

A STATISTICAL COMPARISON OF FIVE GEODETIC GRAVIMETERS

Geophysics ◽  
1962 ◽  
Vol 27 (6) ◽  
pp. 889-891 ◽  
Author(s):  
John C. Behrendt
Keyword(s):  
Standard Deviation ◽  
North American ◽  
Confidence Limit ◽  
Statistical Comparison ◽  
Standard Deviations ◽  
Percent Confidence Limit

A statistical comparison of five LaCoste and Romberg geodetic gravimeters over the 5,129‐mgal North American calibration range shows an estimated standard deviation of 0.17 mgal for the set with a 90‐percent confidence limit of 0.28 mgal. Values for each meter, means and estimated standard deviations are presented for each of the 24 stations included in the set.

scholarly journals The Journey to Work: 25 Years on the Jamaicaway

2010 ◽  
Author(s):  
Carl D. Martland
Keyword(s):  
Steady State ◽  
Standard Deviation ◽  
Economic Analysis ◽  
Network Models ◽  
Traffic Volume ◽  
Travel Time Reliability ◽  
Travel Times ◽  
Recent Period ◽  
Journey To Work ◽  
Work Trip

More than 600 observations were recorded for the author's home-to-work trip for the same route from Boston to Cambridge, Mass., over the period 1980 to 2004. With this data, it is possible to graph the pattern of travel times and travel time reliability as a function of departure times during the morning rush hour. The image of rush hour performance that emerges from this study is more complex than what is often used in network models or abstract economic analysis. For example, as rush hour progresses, variability increases even though expected travel times start to decline. There may also be lulls in rush hour, i.e. intervals of 10-15 minutes when expected trip times and reliability temporarily improve. This type of performance cannot realistically be modeled as a linear function of traffic volume, nor can it be approximated using a steady state queuing analysis. It will be far better to view rush hour performance as a steady state cyclical queuing phenomenon: every day may start afresh, but expected conditions on next Tuesday at 8:30 am are likely to be similar to conditions last Tuesday at that time.Over the 25-year period, there was surprisingly little change in rush hour performance on this congested urban route. Average travel times were mostly in the range of 25-27 minutes with a standard deviation of three to four minutes. There was some spreading of the peak, especially during periods involving major construction, but performance in the most recent period was actually equivalent to performance in the 1980s despite an increase of about 10% in traffic volume. Variability in trip times is mostly related to variability in the delays associated with the most congested

To testing the algorithm for determining earthquake depths by Pn–wave data (the example of Tuvin earthquakes 2011–2012)

2020 ◽  
Author(s):  
Victor M. Solovyev ◽  
◽  
Aleksandr F. Emanov ◽  
Anastasia E. Shenmayer ◽  
Semen A. Elagin ◽  
...  
Keyword(s):  
Local Network ◽  
Travel Times ◽  
Seismic Stations ◽  
Wave Data ◽  
Refracted Waves

The results of determining the depths of aftershocks of the Tuva earthquakes (Tuvinskoe 1 (27.12.2011, ML=6.7) and Tuvinskoe 2 (26.02.2012, ML=6.8)) using the travel times of longitudinal refracted waves from the Mokhorovichich border (Pn–waves) from regional seismic stations are presented. The depth and distribution of aftershock hypocenters obtained by this method correlate with the results from the data of the local network of seismic stations near the Tuva earthquakes.

The Reproducibility of RF Susceptibility Measurements of Electronic Equipment Using a Simple Stripline Circuit

1982 ◽  
Vol 15 (6) ◽  
pp. 229-231
Author(s):  
W. R. Kollewijn
Keyword(s):  
Standard Deviation ◽  
Radio Frequency ◽  
Systematic Difference ◽  
Electronic Equipment ◽  
Frequency Range

The susceptibility of five instruments to radio-frequency (RF) fields has been measured by three laboratories in the frequency range of 27–470 MHz using a simple stripline equipment. There was little systematic difference between the results of the three laboratories. The standard deviation of measurement is estimated to be about 5 dB.

A radiometric age for the Cretaceous–Tertiary boundary based upon K–Ar, Rb–Sr, and U–Pb ages of bentonites from Alberta, Saskatchewan, and Montana

1988 ◽  
Vol 25 (7) ◽  
pp. 1088-1097 ◽  
Author(s):  
H. Baadsgaard ◽  
J. F. Lerbekmo ◽  
I. McDougall
Keyword(s):  
Standard Deviation ◽  
North American ◽  
Red Deer ◽  
Statistical Error ◽  
Systematic Errors ◽  
Stratigraphic Correlation ◽  
Coal Seams ◽  
Weighted Mean ◽  
The North ◽  
Iridium Anomaly

Bentonites associated with coal seams at the North American Cretaceous–Tertiary (K–T) boundary in the Red Deer Valley of Alberta, in the Frenchman Valley of Saskatchewan, and near Hell Creek, Montana, were dated by the K–Ar, Rb–Sr, and U–Pb methods. Based upon palynological stratigraphic correlation and the presence of a sharp iridium anomaly, the three sampled bentonite horizons all occur less than 1 m above the established K–T boundary. There is evidence of possible systematic errors giving dating results outside nominal statistical error values. Despite possible constant errors, the weighted mean of nine average dates is calculated as 64.3 ± 1.2 Ma (2σ standard deviation). An unweighted averaging produces a grand mean age of 64.4 ± 1.2 Ma.

scholarly journals VELOCITY MODEL OF CRUST OF AZERBAIDJAN ON DATA OF DIGITAL SEISMIC STATIONS

2012 ◽  
Author(s):  
Г.Д. Етирмишли ◽  
С.Э. Казымова
Keyword(s):  
Velocity Structure ◽  
Three Dimensional ◽  
Velocity Model ◽  
Design Calculation ◽  
Travel Times ◽  
Seismic Stations ◽  
One Dimensional ◽  
S Waves ◽  
Velocity Models ◽  
Seismological Data

При изучении скоростной структуры земной коры Азербайджана по сейсмологическим данным ис- пользовались в основном два подхода. Первый состоит в уточнении модели среды на основании наблюда- емых отклонений времен пробега волн от землетрясений относительно стандартного годографа. Второй основан на использовании разности времен пробега от источников до станции для групп близко располо- женных событий. Одномерные скоростные модели Р и S-волн были построены на основе одномерных моделей, пред- ложенных в работе Гасанова А.Г. Построение модели, расчет станционных поправок и перелокация со- бытий производились в программе Velest. Исследуемый объем до глубины 60 км был разбит на мелкие слои толщиной 2 км в интервале глубин 010 км и толщиной 510 км в интервале глубин 1060 км. В ходе исследования рассматривались сейсмологические данные о параметрах локальных землетрясений и вре- менах прихода P и S-волн зарегистрированных сетью телеметрических станций за период 20042011 гг. Анализировались данные 28-ми сейсмических станций Азербайджана, охватывающие всю исследуемую территорию. Для расчета трехмерного скоростного поля использовалась программа TomotetraFD. В этой програм- ме реализован классический сейсмотомографический метод для случая, когда источники и приемники находятся внутри исследуемого региона. Two approaches were used for investigation of crust velocity structure of Azerbaijan on the basis of seismological data. The first one consists in medium model adjustment on the basis of observed deviation of travel times of waves from earthquakes relative to standard hodograph. The second is based on difference in travel times from source to station for a group of close located stations. One dimensional velocity models of P- and S-waves were constructed on the basis of one dimensional models proposed by A.G.Gasanov. Model design, calculation of stations corrections and relocationing of events 74 Геология и геофизика Юга России, 1, 2012 were performed in Velest program. Investigating volume to depth of 60 km was divided in small layers of 2 km thickness in 0-10 km interval and 5-10 km in 10-60 km interval. Seismological data about parameters of local earthquakes registered by network of telemetric stations in 2004-2011 and arrival times of P- and S-waves were used. Data of 28 seismic stations of Azerbaijan covering all the investigating territory were analyzed. Three dimensional velocity field was calculated by means of TomotetraFD program. Classical seismotomographical method for the case when sources and receivers are located within investigating region is realized in the program.

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