Microearthquake crustal reflections, Socorro, New Mexico

1965 ◽  
Vol 55 (3) ◽  
pp. 579-586
Author(s):  
A. R. Sanford ◽  
L. T. Long
Keyword(s):  
New Mexico ◽  
Vertical Component ◽  
S Phase ◽  
Distance Data ◽  
Time Distance ◽  
Plane Sv Wave ◽  
Phase Amplitude

Abstract About 25 per cent of the microearthquakes which originate close to Socorro (S minus P ≦ 2.5 secs) produce seismograms with two sharp arrivals about 2.5 and 5.0 seconds after the direct S-phase arrival. The best interpretation of the time-distance data for these late phases is that they are the SxP and the SxS reflections from a crustal discontinuity at a depth of 18 km. The amplitudes of the reflections, which average 0.21 and 0.32 of the direct S-phase amplitude on vertical-component seismograms, are for greater than theoretical amplitudes found by assuming uniform radiation from the focus and reflection of a plane SV wave from a horizontal discontinuity.

scholarly journals Determination of Velocity – Depth Distributions by Inversion of Refraction Time – distance Data: Discussion

1981 ◽  
Vol 12 (3) ◽  
pp. 52-54
Author(s):  
Robert J. Whiteley ◽  
Derecke Palmer ◽  
Stewart Greenhaigh ◽  
David King ◽  
Donald Emerson
Keyword(s):  
Distance Data ◽  
Time Distance ◽  
Depth Distributions

scholarly journals Detecting and locating seismic events with using USArray as a large antenna

2015 ◽  
Vol 40 ◽  
pp. 27-30 ◽  
Author(s):  
L. Retailleau ◽  
N. M. Shapiro ◽  
J. Guilbert ◽  
M. Campillo ◽  
P. Roux
Keyword(s):  
Large Scale ◽  
Seismic Event ◽  
Vertical Component ◽  
Earthquake Detection ◽  
Characteristic Behavior ◽  
Step Procedure ◽  
Teleseismic Waves ◽  
Time Distance ◽  
Location Algorithm ◽  
Global Travel

Abstract. We design an earthquake detection and location algorithm that explores coherence and characteristic behavior of teleseismic waves recorded by a large-scale seismic network. The procedure consists of three steps. First, for every tested source location we construct a time-distance gather by computing great-circle distances to all stations of the network and aligning the signals respectively. Second, we use the constructed gather to compute a Tau-P transform. For waves emitted by teleseismic sources, the amplitude of this transform has a very characteristic behavior with maxima corresponding to different seismic phases. Relative location of these maxima on the time-slowness plane strongly depends on the distance to the earthquake. To explore this dependence, in a third step, we convolve the Tau-P amplitude with a time-slowness filter whose maxima are computed based on prediction of a global travel-time calculator. As a result of this three-step procedure, we obtain a function that characterizes a likelihood of occurrence of a seismic event at a given position in space and time. We test the developed algorithm by applying it to vertical-component records of USArray to locate a set of earthquakes distributed around the Globe with magnitudes between 6.1 and 7.2.

scholarly journals Plasma flows and sound-speed perturbations in the average supergranule

2021 ◽  
Vol 646 ◽  
pp. A184
Author(s):  
David Korda ◽  
Michal Švanda
Keyword(s):  
Travel Time ◽  
Sound Speed ◽  
Deep Structure ◽  
Solar Rotation ◽  
Vertical Component ◽  
Inversion Method ◽  
Time Averaging ◽  
Vertical Flow ◽  
Near Surface ◽  
Time Distance

Context. Supergranules create a peak in the spatial spectrum of photospheric velocity features. Even though they have some properties of convection cells, their origin is still being debated in the literature. The time–distance helioseismology constitutes a method that is suitable for investigating the deep structure of supergranules. Aims. Our aim is to construct the model of the flows in the average supergranular cell using fully consistent time–distance inverse methodology. Methods. We used the Multi-Channel Subtractive Optimally Localised Averaging inversion method with regularisation of the cross-talk. We combined the difference and the mean travel-time averaging geometries. We applied this methodology to travel-time maps averaged over more than 104 individual supergranular cells. These cells were detected automatically in travel-time maps computed for 64 quiet days around the disc centre. The ensemble averaging method allows us to significantly improve the signal-to-noise ratio and to obtain a clear picture of the flows in the average supergranule. Results. We found near-surface divergent horizontal flows which quickly and monotonously weakened with depth; they became particularly weak at the depth of about 7 Mm, where they even apparently switched sign. The amplitude of the ‘reversed’ flow was comparable to the background flows. The inverted vertical flows and sound-speed perturbations were spoiled by unknown systematic errors. To learn about the vertical component, we integrated the continuity equation from the surface. The derived estimates of the vertical flow depicted a sub-surface increase from about 5 m s−1 at the surface to about 35 m s−1 at the depth of about 3 Mm followed by a monotonous decrease to greater depths. The vertical flow remained positive (an upflow) and became indistinguishable from the background at the depth of about 15 Mm. We further detected a systematic flow in the longitudinal direction. The course of this systematic flow with depth agrees well with the model of the solar rotation in the sub-surface layers.

Multiple water reflections recorded at the ocean bottom

1978 ◽  
Vol 15 (1) ◽  
pp. 78-85 ◽  
Author(s):  
George A. McMechan
Keyword(s):  
Vertical Component ◽  
Standard Technique ◽  
Ocean Bottom ◽  
Seismic Profiles ◽  
Multiple Reflections ◽  
Air Water Interface ◽  
Time Distance ◽  
Marine Seismic ◽  
Ray Parameter ◽  
Sediment Interface

The use of direct arrivals and multiple reflections that have travelled completely in water from source to receiver to determine epicentral distances is a standard technique in the analysis of marine seismic profiles. The configuration of a source at the air–water interface and a seismometer at the water–sediment interface is investigated in the ray parameter – distance plane and the travel time – distance plane. Vertical component synthetic seismograms are computed by the Cagniard – de Hoop algorithm and are compared with seismograms recorded at the ocean bottom. The results explain the prominent features of the observed wavetrains, including the asymptotic behaviour of arrivals, the location of caustics and the variable observability of arrivals as a fu nction of distance.

scholarly journals Combined helioseismic inversions for 3D vector flows and sound-speed perturbations

2019 ◽  
Vol 622 ◽  
pp. A163 ◽  
Author(s):  
David Korda ◽  
Michal Švanda
Keyword(s):  
Cross Talk ◽  
Sound Speed ◽  
Vertical Component ◽  
Solar Interior ◽  
Systematic Bias ◽  
Travel Times ◽  
Plasma Flows ◽  
Near Surface ◽  
Time Distance ◽  
The Cross

Context. Time–distance helioseismology is the method of the study of the propagation of waves through the solar interior via the travel times of those waves. The travel times of wave packets contain information about the conditions in the interior integrated along the propagation path of the wave. The travel times are sensitive to perturbations of a variety of quantities. The usual task is to invert for the vector of plasma flows or the sound–speed perturbations separately. The separate inversions may be polluted by systematic bias, for instance, originating in the leakage of vector flows into the sound–speed perturbations and vice versa (called a cross-talk). Information about the cross-talk is necessary for a proper interpretation of results. Aims. We introduce an improved methodology of the time-distance helioseismology which allows us to invert for a full 3D vector of plasma flows and the sound–speed perturbations at once. Using this methodology one can also derive the mean value of the vertical component of plasma flows and the cross-talk between the plasma flows and the sound–speed perturbations. Methods. We used the Subtractive Optimally Localised Averaging method with a minimisation of the cross-talk as a tool for inverse modelling. In the forward model, we use Born approximation travel-time sensitivity kernels with the Model S as a background. The methodology was validated using forward-modelled travel times with both mean and difference point-to-annulus averaging geometries applied to a snapshot of fully self-consistent simulation of the convection. Results. We tested the methodology on synthetic data. We demonstrate that we are able to recover flows and sound–speed perturbations in the near-surface layers. We have taken the advantage of the sensitivity of our methodology to entire vertical velocity, and not only to its variations as in other available methodologies. The cross-talk from both the vertical flow component and the sound–speed perturbation has only a negligible effect for inversions for the horizontal flow components. Furthermore, this cross-talk can be minimised if needed. The inversions for the vertical component of the vector flows or for the sound–speed perturbations are affected by the cross-talk from the horizontal components, which needs to be minimised in order to provide valid results. It seems that there is a nearly constant cross-talk between the vertical component of the vector flows and the sound–speed perturbations.

Guns, Alcohol, and Intimate Partner Violence: The Epidemiology of Female Suicide in New Mexico

Crisis ◽  
1999 ◽  
Vol 20 (3) ◽  
pp. 121-126 ◽  
Author(s):  
Lenora Olson ◽  
Frank Huyler ◽  
Arthur W Lynch ◽  
Lynne Fullerton ◽  
Deborah Werenko ◽  
...  
Keyword(s):  
Intimate Partner Violence ◽  
New Mexico ◽  
American Indians ◽  
Partner Violence ◽  
The United States ◽  
Intimate Partner ◽  
Injury Death ◽  
Female Suicide ◽  
Blood Alcohol Levels ◽  
Associated Risk Factors

Suicide is among the leading causes of death in the United States, and in women the second leading cause of injury death overall. Previous studies have suggested links between intimate partner violence and suicide in women. We examined female suicide deaths to identify and describe associated risk factors. We reviewed all reports from the New Mexico Office of the Medical Investigator for female suicide deaths occurring in New Mexico from 1990 to 1994. Information abstracted included demographics, mechanism of death, presence of alcohol/drugs, clinical depression, intimate partner violence, health problems, and other variables. Annual rates were calculated based on the 1990 census. The New Mexico female suicide death rate was 8.2/100,000 persons per year (n = 313), nearly twice the U. S. rate of 4.5/100,000. Non-Hispanic whites were overrepresented compared to Hispanics and American Indians. Decedents ranged in age from 14 to 93 years (median = 43 years). Firearms accounted for 45.7% of the suicide deaths, followed by ingested poisons (29.1%), hanging (10.5%), other (7.7%), and inhaled poisons (7.0%). Intimate partner violence was documented in 5.1% of female suicide deaths; in an additional 22.1% of cases, a male intimate partner fought with or separated from the decedent immediately preceding the suicide. Nearly two-thirds (65.5%) of the decedents had alcohol or drugs present in their blood at autopsy. Among decedents who had alcohol present (34.5%), blood alcohol levels were far higher among American Indians compared to Hispanics and non-Hispanic Whites (p = .01). Interpersonal conflict was documented in over 25% of cases, indicating that studies of the mortality of intimate partner violence should include victims of both suicide and homicide deaths to fully characterize the mortality patterns of intimate partner violence.

Child and Adolescent Suicide Deaths in New Mexico, 1990-1994

Crisis ◽  
2000 ◽  
Vol 21 (1) ◽  
pp. 36-44 ◽  
Author(s):  
DD Werenko ◽  
LM Olson ◽  
L Fullerton-Gleason ◽  
AW Lynch ◽  
RE Zumwalt ◽  
...  
Keyword(s):  
New Mexico ◽  
Cause Of Death ◽  
American Indians ◽  
Adolescent Suicide ◽  
Suicide Attempts ◽  
Medical Examiner ◽  
Contributing Factors ◽  
Targeted Interventions ◽  
And Gender ◽  
Youth Activity

The suicide death rate in New Mexico is consistently higher than the national rate. Among adolescents, suicide is the third leading cause of death nationally, but in New Mexico it is the second leading cause of death. This study describes the pattern of adolescent suicide deaths in New Mexico. We conducted a retrospective review of all medical examiner autopsies for adolescent suicides (ages 20 years and younger) in New Mexico from 1990-1994. Records were reviewed for demographics and possible contributing factors such as depression, previous attempts, and alcohol and drug use. We identified 184 suicide deaths among children and adolescents ages 9-20 years for an overall rate of 12.9 per 100,000. Our rates for ages 5-9 years (0.2), 10-14 years (3.8), and 15-19 years (22.3) are over twice the U.S. rates. Suicide deaths resulted primarily from firearms (67%), hanging (16%), poisoning (6%), inhalation (4%), and other methods (7%). Method varied by ethnicity (p = .01) and gender (p = .03); males and non-Hispanic Whites were overrepresented among firearm deaths. Firearm ownership was known in 60 (48%) of the firearm deaths. Of these, 53% of the firearms belonged to a family member, 25% to the decedent, and 22% to a friend. Over one-third of decedents (41%) experienced mental disorders, primarily depressed mood and clinical depression. Previous suicide attempts were noted for 15% of the decedents. Some 50% of the decedents had alcohol or drugs present at the time of death; among American Indians/Alaska Natives, 74% had drugs or alcohol present (p = .003). Targeted interventions are needed to reduce adolescent suicide in New Mexico. We suggest raising awareness about acute and chronic contributing factors to suicide; training physicians to look for behavioral manifestations of depression; and involving physicians, teachers, and youth activity leaders in efforts to limit firearm accessibility, such as advising parents to remove firearms from their households.

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