Travel-time study of six central Appalachian earthquakes 1962-1968

1970 ◽  
Vol 60 (2) ◽  
pp. 629-637
Author(s):  
G. A. Bollinger
Keyword(s):  
North Carolina ◽  
Standard Deviation ◽  
Travel Time ◽  
Input Data ◽  
Time Study ◽  
Inverse Slope ◽  
Average Standard Deviation ◽  
Time Curve ◽  
Arrival Times ◽  
Distance Range

abstract Travel time studies are made of the data from six central Appalachian earthquakes that occurred during the period 1962 through 1968 in the states of Virginia, West Virginia, Maryland, and North Carolina. Arrival times from forty-two station-epicenter pairs served as input data for the study. Epicentral locations were obtained for the six events with an average standard deviation for the travel time residuals of 0.5 seconds. Nineteen Pn observations in the distance range of 300 to 800 km yield a composite Pn travel-time curve given by t = ( 8.98 ± 0.14 ) sec + Δ / ( 8.22 ± 0.02 ) km / sec with a 0.19 second standard deviation in the travel-time observations. The inverse slope for the Pg phase was found as 6.24 ± 0.03 km/sec and for the Sg or Lg phases as 3.67 ± 0.02 km/sec. Magnitude determinations using meus of Evernden (1967) are made for two of the five shocks.

A P Travel-Time Model for the Canadian Shield obtained by a Joint Epicenter Determination Method

1974 ◽  
Vol 11 (5) ◽  
pp. 611-618 ◽  
Author(s):  
M. Hashizume
Keyword(s):  
Travel Time ◽  
Canadian Shield ◽  
Time Model ◽  
Time Curve ◽  
Origin Time ◽  
Arrival Times ◽  
Shallow Earthquakes ◽  
Starting Point ◽  
Order Polynomial

The P arrival-times for nine very shallow earthquakes under the Canadian Shield and the surrounding area were studied. P arrival-times were assumed to be a function of the hypocenter, origin-time, and specified travel-time curve. Using as starting point the hypocenters and origin times taken from the Preliminary Determination of Epicenters (PDE) listings and the travel-time curve from the "Seismological Tables for P Phases" by Herrin et al. (1968), calculations were conducted so as to minimize the residuals between the observed P arrival-times and the calculated travel-times in a search for the best hypocenters, origin-times, and travel-time curve. The deviations from the travel-time curve were assumed to be represented by a sixth-order polynomial. The differences of the new epicenters from those of the PDE listings are small and generally less than about 10 km. The significant result is that the new travel-time curve obtained by this technique is similar to those obtained from seismic explosion studies in the eastern part of North America.

scholarly journals Velocity filtering of seismic core phases

1966 ◽  
Vol 56 (2) ◽  
pp. 441-454
Author(s):  
W. J. Hannon ◽  
R. L. Kovach
Keyword(s):  
United States ◽  
Travel Time ◽  
Inner Core ◽  
Linear Array ◽  
Western United States ◽  
Time Curve ◽  
Distance Range ◽  
Velocity Models ◽  
The Core ◽  
Velocity Filtering

abstract Recent studies have proposed complexities in the velocity-depth function for the region surrounding the inner core which require additional branches in the travel time curve for PKP in the epicentral range of 125° to 160°. The proposed PKP arrivals can be separated on the basis of their apparent velocities, which range from 24 km/sec to 100 km/sec. Using the Tonto Forest array in Arizona coupled with adjoining LRSM stations in the western United States, an effective linear array of 400 km in size is attained. Data from several events in the distance range from 130° to 160° recorded on this array have been velocity filtered and show some evidence of two precursors to PKP in the distance range from 135° to 143° and at least one intermediate branch between PKP1 and PKP2 at distances greater than 143°. The results appear to support the velocity solution for the core proposed by Adams and Randall, although more data are required before a conclusive discrimination can be made between competing velocity models.

The Alaskan earthquake of July 22, 1937*

1940 ◽  
Vol 30 (4) ◽  
pp. 353-376
Author(s):  
John N. Adkins
Keyword(s):  
Travel Time ◽  
Epicentral Distance ◽  
Time Interval ◽  
Time Curve ◽  
Arrival Times ◽  
The Earth ◽  
Geographical Latitude ◽  
The World ◽  
First Motion ◽  
First Arrival

Summary The study of the Alaskan earthquake of July 22, 1937, is based on the examination of original seismograms and photographic copies from seismological observatories throughout the world. The arrival times of P at 71 stations were used in locating the epicenter. By Geiger's method and the use of Jeffreys' travel times, the position of the epicenter was found to be: geographical latitude, 64.67±.04° N, longitude, 146.58±.12° W, and the time of occurrence to be 17h 9m 30.0±.25s, U.T. The epicenter lies in the Yukon-Tanana upland in central Alaska, which is not a region of frequent major earthquakes. The disagreement caused by the apparently early arrivals at College and Sitka was reduced by replacing the standard travel-time curve of P by a linear travel-time curve in the interval of epicentral distance 0° to 16° and by interpreting the first arrival at College as P. It was possible to determine the direction of the first motion of P for 51 stations. The observed distribution of first motion and the geological trends in the region of the epicenter are consistent with the earthquake's having been caused by movement along a fault with strike between N 30° E and N 37° E, and dip between 64° and 71° to the southeast, in which the southeast side of the fault was displaced relatively northeastward with the line of movement pitching between 12° and 16° northeast. A wave designated F (for “false S”) was found to precede S on the records by 20 to 55 seconds, depending on the epicentral distance. The wave is longitudinal in type and the arrival times define a linear travel-time curve. It is suggested that this wave may be a longitudinal surface wave, of the type proposed by Nakano, produced at the surface of the earth by the arrival of a transverse wave which has been reflected at a surface of discontinuity within the earth. The records show two impulses near the time when S is expected. The average time interval between the two impulses is 11.3 sec. The first, called S1, has a plane of vibration intermediate in direction between the plane of propagation and the normal thereto. The second impulse, called S2, is nearly pure SH movement. The writer wishes to express his indebtedness to Professor Perry Byerly for invaluable suggestions and criticism during the course of the investigation.

Robust and reliable techniques for epicenter location using time and slowness observations

1990 ◽  
Vol 80 (1) ◽  
pp. 140-149 ◽  
Author(s):  
Frances Cassidy ◽  
Anders Christoffersson ◽  
Eystein S. Husebye ◽  
Bent O. Ruud
Keyword(s):  
Travel Time ◽  
Single Site ◽  
Waveform Data ◽  
Arrival Times ◽  
Distance Range ◽  
Slowness Vector ◽  
Phase Type ◽  
Event Location ◽  
Epicenter Location

Abstract The ever-increasing flow of parameterized and waveform data into various kinds of seismological centers cannot be managed properly unless preliminary epicenter locations are available. Here we demonstrate robust and flexible techniques for fast and reliable event location using the P slowness vector, which is easily derived from arrival times and/or waveform data from arrays, networks, and/or single-site three-component stations. Location schemes are tied to 1) azimuth minimization and 2) slowness vector summation on a sphere using slowness from N arbitrarily positioned stations. The advantage of using azimuth alone is that no assumption is needed of phase type, distance range, or structure (travel-time tables). The viability of our location techniques are demonstrated using a variety of P recordings from networks and three-component stations.

The Hebgen Lake, Montana, earthquake of August 18, 1959: P waves

1962 ◽  
Vol 52 (2) ◽  
pp. 235-271
Author(s):  
Alan Ryall
Keyword(s):  
Travel Time ◽  
Sierra Nevada ◽  
Fault Plane ◽  
Time Curve ◽  
P Waves ◽  
Arrival Times ◽  
The Pacific ◽  
First Motion ◽  
Plane Solution ◽  
The Pacific Ocean

ABSTRACT The instrumental epicenter of the Hebgen Lake earthquake is found to lie within the region of surface faulting. The depth of focus had a maximum value of 25 kilometers. Times of P are studied in detail for epicentral distances less than 13 degrees. The apparent scatter of arrival times from 700 to 1400 kilometers can be explained by variations of the velocity of Pn between the physiographic provinces of the western United States. A comparison of observations for the Hebgen Lake earthquake with published times for blasts in Nevada and Utah indicates that the velocity of Pn in the central and eastern Basin and Range is about 7.5 km/sec, and that the crust in that region thickens toward the east and thins toward the south. A comparison of apparent velocities in northern California, in directions parallel and transverse to the structure, indicates that the crust thins by about 19 kilometers, from the edge of the Sierra Nevada to the Pacific Ocean. A discontinuity is observed in the travel-time curve at a distance of 24–25 degrees. Arrivals of P waves in the range 65–128 degrees fall on two parallel travel-time branches; this multiplicity in the travel-time curve may be related to repeated motion at the source. Travel-times of PKIKP appear to deviate from published curves. The fault-plane solution for the Hebgen Lake earthquake, together with a consideration of the first motion at Bozeman, Montana, indicates a focal mechanism of the dipole, or fault, type. The strike and dip of the instrumental fault plane agree well with observed ruptures at the surface.

Mapping of crack edges by seismic methods

1982 ◽  
Vol 72 (3) ◽  
pp. 779-792
Author(s):  
J. D. Achenbach ◽  
A. Norris ◽  
K. Viswanathan
Keyword(s):  
Input Data ◽  
A Priori ◽  
Signal Propagation ◽  
Computational Procedure ◽  
Crack Edge ◽  
Inverse Mapping ◽  
Arrival Times ◽  
Ultrasonic Signals ◽  
Geometrical Theory Of Diffraction ◽  
Local Edge

abstract The inverse problem of diffraction of elastic waves by the edge of a large crack has been investigated on the basis of elastodynamic ray theory and the geometrical theory of diffraction. Two methods are discussed for the mapping of the edge of a crack-like flaw in an elastic medium. The methods require as input data the arrival times of diffracted ultrasonic signals. The first method maps flash points on the crack edge by a process of triangulation with the source and receiver as given vertices of the triangle. By the use of arrival times at neighboring positions of the source and/or the receiver, the directions of signal propagation, which determine the triangle, can be computed. This inverse mapping is global in the sense that no a priori knowledge of the location of the crack edge is necessary. The second method is a local edge mapping which determines planes relative to a known point close to the crack edge. Each plane contains a flash point. The envelope of the planes maps an approximation to the crack edge. The errors due to inaccuracies in the input data and in the computational procedure have been illustrated by specific examples.

scholarly journals Examination of attitudes of secondary school 6th classstudents related to their attitudes towards maths in the frame of several variables

2016 ◽  
Vol 13 (1) ◽  
pp. 1937
Author(s):  
Kerim Karabacak ◽  
Subhan Eksioglu ◽  
Nesibe Karakıs
Keyword(s):  
Standard Deviation ◽  
Secondary School ◽  
Analysis Of Variance ◽  
Educational Status ◽  
Sixth Grade ◽  
T Test ◽  
Average Standard Deviation ◽  
Statistical Process ◽  
Several Variables ◽  
Purposeful Sampling

This research, which is carried out in Kinik, İzmir, aims at determining the reasons of students’ attitude towards Maths. Sixth class students from Kinik town make up population of the research which has been carried out as the model of survey. The sample of the research has been determined by the method of “purposeful sampling”. It is constituted of 152 students at the sixth grade. Collected data has been transferred into SPSS and the statistical process such as, analysis of average, standard deviation, T-test and one way analysis of variance procedures have been realized. It has been identified that the students who gets higher grades at Maths have got better attitude towards Maths than the ones who got lower grades at Maths. It has been identified that there has been no relationship between the students’ attitude towards Maths and their families’ income, their parents’ educational status, their parents’ occupation and the teachers’ way of teaching.

scholarly journals Modeling Operational Performance of Urban Roads with Heterogeneous Traffic Conditions

2021 ◽  
Author(s):  
Swapneel R. Kodupuganti ◽  
Sonu Mathew ◽  
Srinivas S. Pulugurtha
Keyword(s):  
North Carolina ◽  
Travel Time ◽  
Queue Length ◽  
Simulation Software ◽  
Heterogeneous Traffic ◽  
Operational Performance ◽  
Travel Time Reliability ◽  
Traffic Conditions ◽  
Vehicle Delay ◽  
Blue Line

The rapid growth in population and related demand for travel during the past few decades has had a catalytic effect on traffic congestion, air quality, and safety in many urban areas. Transportation managers and planners have planned for new facilities to cater to the needs of users of alternative modes of transportation (e.g., public transportation, walking, and bicycling) over the next decade. However, there are no widely accepted methods, nor there is enough evidence to justify whether such plans are instrumental in improving mobility of the transportation system. Therefore, this project researches the operational performance of urban roads with heterogeneous traffic conditions to improve the mobility and reliability of people and goods. A 4-mile stretch of the Blue Line light rail transit (LRT) extension, which connects Old Concord Rd and the University of North Carolina at Charlotte’s main campus on N Tryon St in Charlotte, North Carolina, was considered for travel time reliability analysis. The influence of crosswalks, sidewalks, trails, greenways, on-street bicycle lanes, bus/LRT routes and stops/stations, and street network characteristics on travel time reliability were comprehensively considered from a multimodal perspective. Likewise, a 2.5-mile-long section of the Blue Line LRT extension, which connects University City Blvd and Mallard Creek Church Rd on N Tryon St in Charlotte, North Carolina, was considered for simulation-based operational analysis. Vissim traffic simulation software was used to compute and compare delay, queue length, and maximum queue length at nine intersections to evaluate the influence of vehicles, LRT, pedestrians, and bicyclists, individually and/or combined. The statistical significance of variations in travel time reliability were particularly less in the case of links on N Tryon St with the Blue Line LRT extension. However, a decrease in travel time reliability on some links was observed on the parallel route (I-85) and cross-streets. While a decrease in vehicle delay on northbound and southbound approaches of N Tryon St was observed in most cases after the LRT is in operation, the cross-streets of N Tryon St incurred a relatively higher increase in delay after the LRT is in operation. The current pedestrian and bicycling activity levels seemed insignificant to have an influence on vehicle delay at intersections. The methodological approaches from this research can be used to assess the performance of a transportation facility and identify remedial solutions from a multimodal perspective.

scholarly journals Relative Profitability of Maize Production under Different Farm Size Groups in Kishoregonj District of Bangladesh

2013 ◽  
Vol 21 (1-2) ◽  
pp. 247-252 ◽  
Author(s):  
H Uddin ◽  
MHA Rashid ◽  
S Akhter
Keyword(s):  
Standard Deviation ◽  
Farm Size ◽  
Statistical Techniques ◽  
Average Standard Deviation ◽  
Maize Production ◽  
Net Returns ◽  
Size Groups ◽  
Gross Margins ◽  
Relative Profitability

This study was conducted to estimate the relative profitability of Maize production under different farm size groups. Data were collected from randomly selected 74 maize growing farmers of which 25 were small, 32 were medium and 17 were large considering the scope and potentials of maize production at Kishoregonj district. To achieve the objectives of the study, descriptive statistical techniques such as sum, average, standard deviation etc, were used. The major findings of the study showed that per hectare average total costs were Tk. 30,147.54, Tk. 31,892.00 and Tk. 34,059.00 for small, medium and large farmers, respectively. Per hectare gross return from maize production were Tk. 61,730.00, Tk. 79,716.00 and Tk. 75,707.00 for small, medium and large farmers, respectively. Per hectare gross margins from maize production was estimated at Tk. 36,836.00, Tk. 53,096.00 and Tk. 46,871.00 for small, medium and large farmers, respectively. Per hectare average net returns of maize were estimated at Tk. 31,583.00, Tk. 47,823.00 and Tk. 41,648.00 for small, medium and large farmers, respectively. The findings of the study revealed that medium farmers earned higher profit than those of small and large farmers.DOI: http://dx.doi.org/10.3329/pa.v21i1-2.16781 Progress. Agric. 21(1 & 2): 247 - 252, 2010

scholarly journals Deep Meta Tool: GUI tool to obtain Mean and Standard Deviation (SD) from Median and Interquartile range (IQR)

2021 ◽  
Author(s):  
Deepanshu Sharma ◽  
Surya Priya Ulaganathan ◽  
Vinay Sharma ◽  
Sakshi Piplani ◽  
Ravi Ranjan Kumar Niraj
Keyword(s):  
Standard Deviation ◽  
Input Data ◽  
Meta Analysis ◽  
Statistical Procedure ◽  
Interquartile Range ◽  
Raw Data ◽  
Sample Data

Abstract Background and objectivesMeta-analysis is a statistical procedure which enables the researcher to integrate the results of various studies that were conducted for the same purpose. However, more often than not, researchers find themselves in a position unable to proceed further due to the complexity of the mathematics involved and unavailability of raw data. To alleviate the said difficulty, we are presenting a tool that will enable researchers to process raw data.MethodsThe GUI tool is written in python. The tool offers an automated conversion and obtainment of mean and standard deviation (SD) from median and interquartile range, utilizing the methods offered by Hozo et al. 2005 and Bland 2015.ResultsThe tool is tested on some sample data and validation is performed for Bland method on the data provided in the Bland method publication (14).ConclusionsThe provided tool is an easy alternative for the preparation of input data required for clinical meta-analysis in the required format.

Sign in / Sign up

Export Citation Format

Share Document