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.

The collection of seismic station readings

1966 ◽  
Vol 290 (1422) ◽  
pp. 461-471
Keyword(s):  
Reference Point ◽  
Arrival Time ◽  
Seismic Station ◽  
Reference Points ◽  
Origin Time ◽  
Arrival Times ◽  
Starting Point ◽  
Recording Station ◽  
Set Up ◽  
International Seismological Centre

The chief problem of the International Seismological Centre in Edinburgh is to determine focal parameters of seismic events from a stream of station reports. These station reports are identifiable only by the arrival time of the seismic impulse at the given station, as the source location and tim e are not, in general, known when the readings are made. As several events may sometimes occur within a few minutes of each other, and as the P waves from each event may take up to 20 min to reach the points of detection, considerable overlapping is to be expected. One proposal, which will be discussed, is to set up a pattern of reference points covering the Earth, and to subtract the travel time between each reference point and the recording station from the arrival time given in the station report. Each subtraction yields an estimate of what the origin time would have been if the source had been located close to the reference point. If a source actually is close to one of the reference points, the apparent source times form a much sharper ‘bunch’ in a time series than do the arrival times from which they were derived. In addition to assisting recognition, the process yields a provisional epicentre and a set of first residuals and, as such, provides a favourable starting point for the following computations.

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.

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.

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.

Statistical method of steepest improvement of response

2018 ◽  
Vol 84 (11) ◽  
pp. 74-87
Author(s):  
V. B. Bokov
Keyword(s):  
Statistical Method ◽  
Linear Model ◽  
Response Prediction ◽  
Initial Experiment ◽  
First Order ◽  
Prediction Response ◽  
Conditional Extremum ◽  
Order Polynomial ◽  
Limiting Values

A new statistical method for response steepest improvement is proposed. This method is based on an initial experiment performed on two-level factorial design and first-order statistical linear model with coded numerical factors and response variables. The factors for the runs of response steepest improvement are estimated from the data of initial experiment and determination of the conditional extremum. Confidence intervals are determined for those factors. The first-order polynomial response function fitted to the data of the initial experiment makes it possible to predict the response of the runs for response steepest improvement. The linear model of the response prediction, as well as the results of the estimation of the parameters of the linear model for the initial experiment and factors for the experiments of the steepest improvement of the response, are used when finding prediction response intervals in these experiments. Kknowledge of the prediction response intervals in the runs of steepest improvement of the response makes it possible to detect the results beyond their limits and to find the limiting values of the factors for which further runs of response steepest improvement become ineffective and a new initial experiment must be carried out.

Identification of N-Substituted Triazolo-azetidines as Novel Antibacterials using pDualrep2 HTS Platform

2019 ◽  
Vol 22 (5) ◽  
pp. 346-354
Author(s):  
Yan A. Ivanenkov ◽  
Renat S. Yamidanov ◽  
Ilya A. Osterman ◽  
Petr V. Sergiev ◽  
Vladimir A. Aladinskiy ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Large Scale ◽  
Underlying Mechanism ◽  
Luciferase Assay ◽  
Reporter System ◽  
E Coli ◽  
Starting Point ◽  
High Concentrations ◽  
Mic Value

Aim and Objective: Antibiotic resistance is a serious constraint to the development of new effective antibacterials. Therefore, the discovery of the new antibacterials remains one of the main challenges in modern medicinal chemistry. This study was undertaken to identify novel molecules with antibacterial activity. Materials and Methods: Using our unique double-reporter system, in-house large-scale HTS campaign was conducted for the identification of antibacterial potency of small-molecule compounds. The construction allows us to visually assess the underlying mechanism of action. After the initial HTS and rescreen procedure, luciferase assay, C14-test, determination of MIC value and PrestoBlue test were carried out. Results: HTS rounds and rescreen campaign have revealed the antibacterial activity of a series of Nsubstituted triazolo-azetidines and their isosteric derivatives that has not been reported previously. Primary hit-molecule demonstrated a MIC value of 12.5 µg/mL against E. coli Δ tolC with signs of translation blockage and no SOS-response. Translation inhibition (26%, luciferase assay) was achieved at high concentrations up to 160 µg/mL, while no activity was found using C14-test. The compound did not demonstrate cytotoxicity in the PrestoBlue assay against a panel of eukaryotic cells. Within a series of direct structural analogues bearing the same or bioisosteric scaffold, compound 2 was found to have an improved antibacterial potency (MIC=6.25 µg/mL) close to Erythromycin (MIC=2.5-5 µg/mL) against the same strain. In contrast to the parent hit, this compound was more active and selective, and provided a robust IP position. Conclusion: N-substituted triazolo-azetidine scaffold may be used as a versatile starting point for the development of novel active and selective antibacterial compounds.

Theoretical determination of the structures of CaSiO3 perovskites

2006 ◽  
Vol 62 (6) ◽  
pp. 1025-1030 ◽  
Author(s):  
Razvan Caracas ◽  
Renata M. Wentzcovitch
Keyword(s):  
Crystal Structure ◽  
Experimental Data ◽  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Determination ◽  
Functional Theory ◽  
Starting Point ◽  
Atomic Coordinates ◽  
The Ideal

Density functional theory is used to determine the possible crystal structure of the CaSiO3 perovskites and their evolution under pressure. The ideal cubic perovskite is considered as a starting point for studying several possible lower-symmetry distorted structures. The theoretical lattice parameters and the atomic coordinates for all the structures are determined, and the results are discussed with respect to experimental data.

Choice of a teleseismicP-wave travel-time model and the associated source corrections

1972 ◽  
Vol 101 (1) ◽  
pp. 74-89
Author(s):  
S. K. Arora ◽  
C. A. Krishnan
Keyword(s):  
Travel Time ◽  
Time Model ◽  
Wave Travel

Moment-tensor solutions for the 24 November 1987 Superstition Hills, California, earthquakes

1989 ◽  
Vol 79 (2) ◽  
pp. 493-499
Author(s):  
Stuart A. Sipkin
Keyword(s):  
Main Shock ◽  
Moment Tensor ◽  
Time Dependent ◽  
Origin Time ◽  
Data Set ◽  
Filter Theory ◽  
Long Period ◽  
Seismograph Network ◽  
Scalar Moment

Abstract The teleseismic long-period waveforms recorded by the Global Digital Seismograph Network from the two largest Superstition Hills earthquakes are inverted using an algorithm based on optimal filter theory. These solutions differ slightly from those published in the Preliminary Determination of Epicenters Monthly Listing because a somewhat different, improved data set was used in the inversions and a time-dependent moment-tensor algorithm was used to investigate the complexity of the main shock. The foreshock (origin time 01:54:14.5, mb 5.7, Ms 6.2) had a scalar moment of 2.3 × 1025 dyne-cm, a depth of 8 km, and a mechanism of strike 217°, dip 79°, rake 4°. The main shock (origin time 13:15:56.4, mb 6.0, Ms 6.6) was a complex event, consisting of at least two subevents, with a combined scalar moment of 1.0 × 1026 dyne-cm, a depth of 10 km, and a mechanism of strike 303°, dip 89°, rake −180°.

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