Rapid Estimation of Earthquake Magnitude from the Arrival Time of the Peak High‐Frequency Amplitude

2016 ◽  
Vol 106 (1) ◽  
pp. 232-241 ◽  
Author(s):  
Shunta Noda ◽  
Shunroku Yamamoto ◽  
William L. Ellsworth
Keyword(s):  
High Frequency ◽  
Arrival Time ◽  
Earthquake Magnitude ◽  
Rapid Estimation

On the effectiveness of ventilation to mitigate the damage of spherical membrane vessels subjected to internal detonations

2020 ◽  
Vol 11 (3) ◽  
pp. 319-339
Author(s):  
Francisco Hernandez ◽  
Xihong Zhang ◽  
Hong Hao
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
High Frequency ◽  
Arrival Time ◽  
Time Lag ◽  
Reflected Shock Wave ◽  
High Explosives ◽  
Element Analysis ◽  
Blast Overpressure ◽  
Reflected Shock

This article conducts a comparative study on the effectiveness of ventilation to mitigate blasting effects on spherical chambers subjected to internal detonations of high explosives through finite element analysis using the software package AUTODYN. Numerical simulations show that ventilation is ineffective in mitigating the damage of spherical chambers subjected to internal high explosives explosions because the chamber response is mainly described by high-frequency membrane modes. Openings do not reduce the chamber response despite they can reduce the blast overpressure after the chamber reaches its peak response. Worse still, openings lead to stress concentration, which weakens the structure. Therefore, small openings may reduce the capacity of the chamber to resist internal explosions. In addition, because large shock waves impose the chamber to respond to a reverberation frequency associated with the re-reflected shock wave pulses, secondary re-reflected shock waves can govern the chamber response, and plastic/elastic resonance can occur to the chamber. Simulations show that the time lag between the first and the second shock wave ranges from 3 to 7 times the arrival time of the first shock wave, implying that the current simplified design approach should be revised. The response of chambers subjected to eccentric detonations is also studied. Results show that due to asymmetric explosions, other membrane modes may govern the chamber response and causes localized damage, implying that ventilation is also ineffective to mitigate the damage of spherical chambers subjected to eccentric detonations.

INTERPRETATION OF THE TRANSIENT BEHAVIOR OF THE REFLECTION SEISMOGRAPH

Geophysics ◽  
1942 ◽  
Vol 7 (2) ◽  
pp. 123-132 ◽  
Author(s):  
R. G. Piety
Keyword(s):  
High Frequency ◽  
Arrival Time ◽  
Graphical Method ◽  
Transient Behavior ◽  
Unit Impulse ◽  
Impulsive Response ◽  
Actual Response ◽  
Method Of Design

This paper discusses a method of design for the reflection seismograph based on the galvanometer response when the geophone is subject to a unit impulse. A graphical method of obtaining the actual response to an arbitrary geophone motion in terms of the impulsive response is given. A family of desirable types of impulsive response is obtained by analyzing the implications of this graphical computation when strong low and high frequency interference is present. The application of this method of computation to the evaluation of corrections in the apparent arrival time of reflections obtained with different instruments is outlined.

A NEW METHOD FOR THE RAPID ESTIMATION OF MOISTURE IN WHEAT

1929 ◽  
Vol 1 (2) ◽  
pp. 155-162 ◽  
Author(s):  
E. F. Burton ◽  
Arnold Pitt
Keyword(s):  
Moisture Content ◽  
Electric Field ◽  
Rapid Method ◽  
High Frequency ◽  
Alternating Current ◽  
New Method ◽  
Rapid Estimation ◽  
Alternating Electric Field

A rapid method of estimating the moisture in a sample of wheat is described. This method depends on the effect produced in a specially arranged radio circuit in which an alternating current of high frequency is generated. When a container holding some of the wheat under examination is introduced into the rapidly alternating electric field, a change occurs in the strength of the current which may be measured by an ammeter in the circuit and which may be immediately interpreted as a measure of the moisture content of the wheat.

scholarly journals GABA Shapes Selectivity for the Rate and Direction of Frequency-Modulated Sweeps in the Auditory Cortex

2009 ◽  
Vol 102 (3) ◽  
pp. 1366-1378 ◽  
Author(s):  
Khaleel A. Razak ◽  
Zoltan M. Fuzessery
Keyword(s):  
Auditory Cortex ◽  
Gabaa Receptor ◽  
Gabaa Receptors ◽  
High Frequency ◽  
Arrival Time ◽  
Low Frequency ◽  
Direction Selectivity ◽  
Similar Response ◽  
Cortical Level ◽  
Pallid Bat

In the pallid bat auditory cortex and inferior colliculus (IC), the majority of neurons tuned in the echolocation range is selective for the direction and rate of frequency-modulated (FM) sweeps used in echolocation. Such selectivity is shaped mainly by spectrotemporal asymmetries in sideband inhibition. An early-arriving, low-frequency inhibition (LFI) shapes direction selectivity. A delayed, high-frequency inhibition (HFI) shapes rate selectivity for downward sweeps. Using iontophoretic blockade of GABAa receptors, we show that cortical FM sweep selectivity is at least partially shaped locally. GABAa receptor antagonists, bicuculline or gabazine, reduced or eliminated direction and rate selectivity in ∼50% of neurons. Intracortical GABA shapes FM sweep selectivity by either creating the underlying sideband inhibition or by advancing the arrival time of inhibition relative to excitation. Given that FM sweep selectivity and asymmetries in sideband inhibition are already present in the IC, these data suggest a refinement or recreation of similar response properties at the cortical level.

Pulsar Timing Observations at Tidbinbilla

1976 ◽  
Vol 3 (1) ◽  
pp. 81-83 ◽  
Author(s):  
R. N. Manchester ◽  
W. M. Goss ◽  
Lynette M. Newton ◽  
P. A. Hamilton
Keyword(s):  
Faraday Rotation ◽  
High Frequency ◽  
Pulse Shape ◽  
Arrival Time ◽  
Dispersion Measure ◽  
Pulse Arrival Time ◽  
Pulsar Timing ◽  
One Year ◽  
Pulse Arrival

Pulse arrival time measurements allow the determination of accurate pulsar periods, period derivatives and, provided the data span is at least one year, precise pulsar positions. If observations are frequent and reasonably regular, irregularities in the period can also be investigated. To minimize the effect of possible variations in dispersion measure, it is important that these observations be made at a relatively high frequency, preferably above 1 GHz. To eliminate pulse shape variations due to variable ionospheric Faraday rotation, the pulse total intensity or one of the circular polarizations must be recorded.

Ground Failure from the Anchorage, Alaska, Earthquake of 30 November 2018

2019 ◽  
Vol 91 (1) ◽  
pp. 19-32 ◽  
Author(s):  
Randall W. Jibson ◽  
Alex R. R. Grant ◽  
Robert C. Witter ◽  
Kate E. Allstadt ◽  
Eric M. Thompson ◽  
...  
Keyword(s):  
High Frequency ◽  
Ground Deformation ◽  
Earthquake Magnitude ◽  
Rock Falls ◽  
Ground Failure ◽  
Port Facilities ◽  
Significant Damage ◽  
Earth Flows ◽  
1964 Alaska ◽  
Alaska Earthquake

Abstract Investigation of ground failure triggered by the 2018 Mw 7.1 Anchorage earthquake showed that landslides, liquefaction, and ground cracking all occurred and caused significant damage. Shallow rock falls and rock slides were the most abundant types of landslides, but they occurred in smaller numbers than global models that are based on earthquake magnitude predict; this might result from the 2018 earthquake being an intraslab event. Liquefaction was common in alluvial and intertidal areas; ground deformation probably related to liquefaction damaged numerous houses and port facilities in Anchorage. Ground cracking was pervasive near the edges of slopes in hilly areas and caused perhaps the most significant property damage of all types of ground failure. A complex of slump–earth flows was triggered along coastal bluffs in southern Anchorage where slides also occurred in 1964; the 2018 slides involved both mobilization of new landside material and reactivation of parts of the 1964 landslide deposits. Large translational slides that formed during the 1964 Alaska earthquake showed evidence of deformation along pre‐existing failure surfaces but did not reactivate with new net downslope displacement. Modeling suggests that ground motion in 2018 was of insufficient duration and too high frequency to trigger reactivation of the deep landslides.

Auditory Mechanisms of Echolocation in Bats

2018 ◽  
Author(s):  
Cynthia F. Moss
Keyword(s):  
High Frequency ◽  
Arrival Time ◽  
Brain Regions ◽  
Frequency Content ◽  
Complete Darkness ◽  
3D Perception ◽  
Sensing System ◽  
Motor Circuits ◽  
Premotor Neurons ◽  
Sonar Echoes

Echolocating bats have evolved an active sensing system, which supports 3D perception of objects in the surroundings and permits spatial navigation in complete darkness. Echolocating animals produce high frequency sounds and use the arrival time, intensity, and frequency content of echo returns to determine the distance, direction, and features of objects in the environment. Over 1,000 species of bats echolocate with signals produced in their larynges. They use diverse sonar signal designs, operate in habitats ranging from tropical rain forest to desert, and forage for different foods, including insects, fruit, nectar, small vertebrates, and even blood. Specializations of the mammalian auditory system, coupled with high frequency hearing, enable spatial imaging by echolocation in bats. Specifically, populations of neurons in the bat central nervous system respond selectively to the direction and delay of sonar echoes. In addition, premotor neurons in the bat brain are implicated in the production of sonar calls, along with movement of the head and ears. Audio-motor circuits, within and across brain regions, lay the neural foundation for acoustic orientation by echolocation in bats.

Neural Mechanisms Underlying Selectivity for the Rate and Direction of Frequency-Modulated Sweeps in the Auditory Cortex of the Pallid Bat

2006 ◽  
Vol 96 (3) ◽  
pp. 1303-1319 ◽  
Author(s):  
Khaleel A. Razak ◽  
Zoltan M. Fuzessery
Keyword(s):  
Auditory Cortex ◽  
High Frequency ◽  
Cortical Neurons ◽  
Arrival Time ◽  
Narrow Band ◽  
Low Frequency ◽  
Sweep Rate ◽  
Direction Selectivity ◽  
Pallid Bats ◽  
Pallid Bat

Frequency-modulated (FM) sweeps are common in vocalizations, including human speech. Selectivity for FM sweep rate and direction is present in the auditory cortex of many species. The present study sought to determine the mechanisms underlying FM sweep selectivity in the auditory cortex of pallid bats. In the pallid bat inferior colliculus (IC), two mechanisms underlie selectivity for FM sweep rate. The first mechanism depends on duration tuning for tones that arises as a consequence of early inhibition generated by an excitatory tone. The second mechanism depends on a narrow band of delayed high-frequency inhibition. Direction selectivity depends on a broad band of early low-frequency inhibition. Here, the contributions of these mechanisms to cortical FM sweep selectivity were determined in pentobarbital-anesthetized pallid bats. We show that the majority of cortical neurons tuned to echolocation frequencies are selective for the downward direction and rate of FM sweeps. Unlike in IC neurons tuned in the echolocation range, duration tuning is rare in cortical neurons with similar tuning. As in the IC, consistent spectrotemporal differences exist between low- and high-frequency sidebands. A narrow band of delayed high-frequency inhibition is necessary for FM rate selectivity. Low-frequency inhibition has a broad bandwidth, early arrival time, and creates direction selectivity. Cortical neurons respond better to slower FM rates and exhibit broader rate tuning than IC neurons. Relative arrival time of high-frequency inhibition is slower in the cortex than in the IC. Thus whereas similar mechanisms shape direction selectivity of neurons tuned in the echolocation range in the IC and the cortex, only one of the two mechanisms underlying rate selectivity in the IC is present in the cortex.

scholarly journals Differential roles of GABAergic and glycinergic input on FM selectivity in the inferior colliculus of the pallid bat

2011 ◽  
Vol 106 (5) ◽  
pp. 2523-2535 ◽  
Author(s):  
Anthony J. Williams ◽  
Zoltan M. Fuzessery
Keyword(s):  
Inferior Colliculus ◽  
Auditory System ◽  
High Frequency ◽  
Arrival Time ◽  
Drug Application ◽  
Low Frequency ◽  
Direction Selectivity ◽  
Central Nucleus ◽  
System 2 ◽  
Pallid Bat

Multiple mechanisms have been shown to shape frequency-modulated (FM) selectivity within the central nucleus of the inferior colliculus (IC) in the pallid bat. In this study we focus on the mechanisms associated with sideband inhibition. The relative arrival time of inhibition compared with excitation can be used to predict FM responses as measured with a two-tone inhibition paradigm. An early-arriving low-frequency inhibition (LFI) prevents responses to upward sweeps and thus shapes direction selectivity. A late-arriving high-frequency inhibition (HFI) suppresses slow FM sweeps and thus shapes rate selectivity for downward sweeps. Iontophoretic application of gabazine (GBZ) to block GABAA receptors or strychnine (Strych) to block glycine receptors was used to assess the effects of removal of inhibition on each form of FM selectivity. GBZ and Strych had a similar effect on FM direction selectivity, reducing selectivity in up to 86% of neurons when both drugs were coapplied. FM rate selectivity was more resistant to drug application with less than 38% of neurons affected. In addition, only Strych could eliminate FM rate selectivity, whereas GBZ alone was ineffective. The loss of FM selectivity was directly correlated to a loss of the respective inhibitory sideband that shapes that form of selectivity. The elimination of LFI correlated to a loss of FM direction selectivity, whereas elimination of HFI correlated to a loss of FM rate selectivity. Results indicate that 1) although the majority of FM direction selectivity is created within the IC, the majority of rate selectivity is inherited from lower levels of the auditory system, 2) a loss of LFI corresponds to a loss of FM direction selectivity and is created through either GABAergic or glycinergic input, and 3) a loss of HFI corresponds to a loss of FM rate selectivity and is created mainly through glycinergic input.

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