Erratum to the KHC Seismic Station: The Birthplace of Broadband Seismology

2020 ◽  
Author(s):  
Petr Kolář
Keyword(s):  
Seismic Station ◽  
Broadband Seismology

The KHC Seismic Station: The Birthplace of Broadband Seismology

2020 ◽  
Vol 91 (2A) ◽  
pp. 1057-1063 ◽  
Author(s):  
Petr Kolář
Keyword(s):  
Data Mining ◽  
Scientific Literature ◽  
Seismic Station ◽  
Broadband Seismometer ◽  
Time Period ◽  
The Social ◽  
Broadband Seismology ◽  
Original Works

Abstract Nearly half a century has passed since the first broadband seismometer was installed by A. Plešinger and his team. The principles behind this instrument, as well as its features and new possibilities regarding broadband data mining, have been reported within the scientific literature. This text is intended as a commemoration of this pioneering work and also serves as a historical reminder of the social and political circumstances surrounding the time period of broadband seismometer introduction that are not mentioned in original works but that played an important role during broadband seismometer development.

scholarly journals Indicators for site characterization at seismic station: recommendation from a dedicated survey

2021 ◽  
Author(s):  
Giovanna Cultrera ◽  
Cécile Cornou ◽  
Giuseppe Di Giulio ◽  
Pierre-Yves Bard
Keyword(s):  
Seismic Station ◽  
International Workshop ◽  
Site Characterization ◽  
Companion Paper ◽  
Background Information ◽  
Online Questionnaire ◽  
Seismic Records ◽  
Seismic Networks ◽  
High Level ◽  
Data Acquisition And Processing

AbstractIn recent years, the permanent seismic networks worldwide have largely increased, raising the amount of earthquake signals and the applications using seismic records. Although characterization of the soil properties at recording stations has a large impact on hazard estimates, it has not been implemented so far in a standardized way for reaching high-level metadata. To address this issue, we built an online questionnaire for the identification of the indicators useful for a reliable site characterization at a seismic station. We analysed the answers of a large number of experts in different fields, which allowed us to rank 24 different indicators and to identify the most relevant ones: fundamental frequency (f0), shear-wave velocity profile (VS), time-averaged Vs over 30 m (VS30), depth of seismological and engineering bedrock (Hseis_bed and Heng_bed), surface geology and soil class. Moreover, the questionnaire proposed two additional indices in terms of cost and difficulty to obtain a reliable value of each indicator, showing that the selection of the most relevant indicators results from a complex balance between physical relevancy, average cost and reliability. For each indicator we propose a summary report, provided as editable pdf, containing the background information of data acquisition and processing details, with the aim to homogenize site metadata information at European level and to define the quality of the site characterization (see companion paper Di Giulio et al. 2021). The selected indicators and the summary reports have been shared within European and worldwide scientific community and discussed in a dedicated international workshop. They represent a first attempt to reach a homogeneous set of high-level metadata for site characterization.

scholarly journals Fluid activity detection in geothermal areas using a single seismic station by monitoring horizontal-to-vertical spectral ratios

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kyosuke Okamoto ◽  
Hiroshi Asanuma ◽  
Hiro Nimiya
Keyword(s):  
Carbon Capture ◽  
Seismic Station ◽  
Carbon Capture And Storage ◽  
Fluid Flows ◽  
Temporal Variations ◽  
Geothermal Field ◽  
Spectral Ratios ◽  
Subsurface Structures ◽  
Geothermal Fields ◽  
Single Station

AbstractSubsurface structure survey based on horizontal-to-vertical (H/V) spectral ratios is widely conducted. The major merit of this survey is its convenience to obtain a stable result using a single station. Spatial variations of H/V spectral ratios are well-known phenomena, and it has been used to estimate the spatial fluctuation in subsurface structures. It is reasonable to anticipate temporal variations in H/V spectral ratios, especially in areas like geothermal fields, carbon capture and storage fields, etc., where rich fluid flows are expected, although there are few reports about the temporal changes. In Okuaizu Geothermal Field (OGF), Japan, dense seismic monitoring was deployed in 2015, and continuous monitoring has been consistent. We observed the H/V spectral ratios in OGF and found their repeated temporary drops. These drops seemed to be derived from local fluid activities according to a numerical calculation. Based on this finding, we examined a coherency between the H/V spectral ratios and fluid activities in OGF and found a significance. In conclusion, monitoring H/V spectral ratios can enable us to grasp fluid activities that sometimes could lead to a relatively large seismic event.

On the reliability of PKIIKP phase identification at a single station

2021 ◽  
Author(s):  
Olga Usoltseva ◽  
Vladimir Ovtchinnikov
Keyword(s):  
Inner Core ◽  
Seismic Velocity ◽  
Seismic Station ◽  
Shear Velocity ◽  
Outer Core ◽  
Joint Analysis ◽  
Time Range ◽  
Model Parameters ◽  
Phase Identification ◽  
Single Station

<p><span>Study of the contact zone between the inner and outer core represents considerable interest for understanding of properties, structures and dynamic of the Earth's core. One of </span><span>the </span><span>sources of </span><span>the </span><span>data about the processes proceeding in the top part of the inner core is the seismic wave PKIIKP once reflected from an undersize inner core boundary. Amplitudes of these waves are sensitive to the shear velocity in the top part of the inner core and are small. Therefore their identification at a single seismic station is not reliable without application of additional methods of analysis. </span><span>Significant in this regard is the discussion about the source (in inner core or in mantle) of anomalous arrivals<!-- Это можно удалить --> detected at the TAM station in North Africa [1,2] in the time range of PKIIKP phase.</span></p><p><span>To estimate influence of model parameters (S and P seismic velocity) on the characteristics of PKIIKP wave (amplitude and travel time) we calculated sensitivity kernels for upper mantle and inner core for dominant period 1.2 s, azimuth step 0.2 degrees and radius step 20 km by using DSM Kernel Suite algorithm. It was revealed that PKIIKP amplitude is more sensitivities to mantle heterogeneities than to inner core ones. </span><span>For reducing the effects of the overlying structures we suppose to use </span>а <span>joint analysis PKIIKP and pPKIIKP waves. </span><span>With this approach, an incorrect i</span><span>dentification</span><span> of the PKIIKP wave is most likely excluded. </span><span>We<!-- Было бы хорошо привести пример --> demonstrate the effectiveness of the approach on the example of processing the seismogram of the 11.02.2015 earthquake re</span>с<span>o</span><span>rded at the GZH station in China at a distance of 179.4 degrees.</span></p><p><span>1. Wang W., Song X. Analyses of anomalous amplitudes of antipodal PKIIKP waves</span><span>,</span><span> E<!-- Удаляется вместе с текстом, выделенным выше Зеленым цветом. -->aPP. 2019. V. 3. P. 212-217. doi: 10.26464/epp2019023</span></p><p><span>2. Tsuboi S., Butler R. Inner core differential rotation inferred from antipodal seismic observations</span><span>,</span><span> PEPI</span><span>,</span><span> 2020. V.301. 106451. </span></p>

The Chelmsford-Lowell, Massachusetts, earthquake of 23 November 1980: Depth control and fault plane solution

1981 ◽  
Vol 71 (4) ◽  
pp. 1369-1372
Author(s):  
Jay J. Pulli ◽  
Michael J. Guenette
Keyword(s):  
New England ◽  
Fault Plane ◽  
Seismic Station ◽  
Focal Depth ◽  
Strike Slip ◽  
Fault Plane Solution ◽  
Origin Time ◽  
Small Magnitude ◽  
Depth Control ◽  
Plane Solution

abstract On 23 November 1980, a small (magnitude 2.9) earthquake occurred on the Chelmsford-Lowell, Massachusetts, border, approximately 10 km northeast of the MIT seismic station at Westford, Massachusetts (WFM). Thus we were able to accurately determine the focal depth, which is generally not the case in New England. Our hypocentral solution was latitude 41.63, longitude −71.36, depth 1.5 km, at origin time 00:39:32.0 UTC. The fault plane solution shows either strike-slip or dip-slip faulting with a P axis trending NE-SW, which is in agreement with overcoring measurements in a nearby granite quarry.

Spectral ratio comparison between translation and rotational records from induced seismic events.

2021 ◽  
Author(s):  
Dariusz Nawrocki ◽  
Maciej Mendecki ◽  
Lesław Teper
Keyword(s):  
Seismic Data ◽  
Seismic Station ◽  
Spectral Ratio ◽  
Numerical Differentiation ◽  
Vertical Axis ◽  
Frequency Range ◽  
Signal Ratio ◽  
Seismic Waveforms ◽  
Seismic Tests ◽  
Rotation Spectrum

<p>The seismic observations of the rotational signals are a field of seismology that is constantly developed. The recent research concerns sensors technology and its potential application in seismic tests. This study presents the results of a comparative analysis of rotational and translational seismic records using the horizontal-to-vertical spectral ratio (HVSR) method. In terms of transitional signal ratio, we have used the name of HVSR, but in terms of rotational component spectra, we have introduced a torsion-to-rocking spectral ratio (TRSR) which corresponds to horizontal rotation spectrum to vertical rotation spectrum. It has to be noticed that rotation in the horizontal axes has a vertical character and rotation in the vertical axis has a horizontal character.</p><p>The comparison was carried out between velocity signals of translational and rotational records, as well as, between acceleration signals respectively. All seismic data were recorded by two independent sensors: the rotational seismometer and translational accelerometer at the Imielin station, located in the Upper Silesia Coal Basin (USCB), Poland. The seismic data composed of three-component seismic waveforms related to 56 recorded tremors which were located up to 1,5 km from the seismic station and they resulted from the coal extractions carried out in the neighboring coal mines. The rotational acceleration was obtained by numerical differentiation and the translational velocity was produced by numerical integration.</p><p>The conducted spectral analyses allowed to estimate the range of frequency in which the rotational HVSR and the corresponded translational HVSR are comparable. The analysis of HVSR/TRSR curves (in the selected frequency range of 1Hz to 10Hz) showed a strong correlation between the spectral ratios for the velocity signals (translational and rotational) in the frequency range of 1Hz to 2Hz. Respectively, the comparison of the accelerometer signals indicated the correlation between HVSR/TRSR curves in the frequency range of 1Hz to 3Hz. Moreover, both of the TRSR (for velocity and acceleration) showed additional maxima in the same frequency range of 3Hz to 5Hz. These relatively high-frequency maxima did not correspond to translational spectra.  </p>

Geographical interpretation of measurements of average phase velocities of surface waves over great circular and great semi-circular paths

1964 ◽  
Vol 54 (2) ◽  
pp. 571-610
Author(s):  
George E. Backus
Keyword(s):  
Spherical Harmonics ◽  
Rayleigh Waves ◽  
Seismic Station ◽  
Great Circle ◽  
Explicit Formulas ◽  
Phase Velocities ◽  
Rapid Accumulation ◽  
Generalized Spherical Harmonics ◽  
Geographical Position ◽  
The Difference

ABSTRACT If the averages of the reciprocal phase velocity c−1 of a given Rayleigh or Love mode over various great circular or great semicircular paths are known, information can be extracted about how c−1 varies with geographical position. Assuming that geometrical optics is applicable, it is shown that if c−1 is isotropic its great circular averages determine only the sum of the values of c−1 at antipodal points and not their difference. The great semicircular averages determine the difference as well. If c−1 is anisotropic through any cause other than the earth's rotation, even great semicircular averages do not determine c−1 completely. Rotation has negligible effect on Love waves, and if it is the only anisotropy present its effect on Rayleigh waves can be measured and removed by comparing the averages of c−1 for the two directions of travel around any great circle not intersecting the poles of rotation. Only great circular and great semicircular paths are considered because every earthquake produces two averages of c−1 over such paths for each seismic station. No other paths permit such rapid accumulation of data when the azimuthal variations of the earthquakes' radiation patterns are unknown. Expansion of the data in generalized spherical harmonics circumvents the fact that the explicit formulas for c−1 in terms of its great circular or great semicircular integrals require differentiation of the data. Formulas are given for calculating the generalized spherical harmonics numerically.

Three-component analysis of regional seismograms

1990 ◽  
Vol 80 (6B) ◽  
pp. 2032-2052 ◽  
Author(s):  
D. C. Jepsen ◽  
B. L. N. Kennett
Keyword(s):  
Free Surface ◽  
Time Window ◽  
Seismic Station ◽  
P Wave ◽  
Sh Waves ◽  
Near Surface ◽  
Source Discrimination ◽  
Decomposition Scheme ◽  
Phased Array Techniques ◽  
The Stability

Abstract Both phased array techniques for single-component sensors and vectorial analysis of three-component recordings can provide estimates of the azimuth and slowness of seismic phases. However, a combination of these approaches provides a more powerful tool to estimate the propagation characteristics of different seismic phases at regional distances. Conventional approaches to the analysis of three-component seismic records endeavor to exploit the apparent angles of propagation in horizontal and vertical planes as well as the polarization of the waves. The basic assumption is that for a given time window there is a dominant wavetype (e.g., a P wave) traveling in a particular direction arriving at the seismic station. By testing a range of characteristics of the three-component records, a set of rules can be established for classifying much of the seismogram in terms of wavetype and direction. It is, however, difficult to recognize SH waves in the presence of other wavetypes. Problems also arise when more than one signal (in either wavetype or direction) arrive in the same window. The stability and robustness of the classification scheme is much improved when records from an array of three-component sensors are combined. For a set of three-component instruments forming part of a larger array, it is possible to estimate the slowness and azimuth of arrivals from the main array and then extract the relative proportions of the current P-, SV-, and SH-wave contributions to the seismogram. This form of wavetype decomposition depends on a model of near-surface propagation. A convenient choice for hard-rock sites is to include just the effect of the free surface, which generates a frequency-independent operation on the three-component seismograms and which is not very sensitive to surface velocities. This approach generates good estimates of the character of the S wavefield, because the phase distortion of SV induced by the free surface can be removed. The method has been successfully applied to regional seismograms recorded at the medium aperture Warramunga array in northern Australia, and the two small arrays NORESS and ARCESS in Norway, which were designed for studies of regional phases. The new wavefield decomposition scheme provides results in which the relative proportions of P, SV, and SH waves as a function of time can be compared without the distortion imposed by free surface amplification. Such information can provide a useful adjunct to existing measures of signal character used in source discrimination.

scholarly journals Results of the infrasonic array on the Valaam Island primary data processing

2020 ◽  
Vol 2 (1) ◽  
pp. 85-91
Author(s):  
Vladimir Karpinsky ◽  
Vladimir Asming
Keyword(s):  
Data Processing ◽  
Seismic Station ◽  
Sampling Rate ◽  
Low Frequency ◽  
Primary Data ◽  
Joint Analysis ◽  
Main Task ◽  
Significant Difference ◽  
Infrasound Signal ◽  
Short Time

The infrasound array VALS developed in Kola Branch GS RAS has been installed in June 2016 on the Valaam Island in addition to the continuously operating seismic station VALR. The array consists of 3 spaced low-frequency microphones. The data with a sampling rate of 100 Hz is stored continuously at the acquisition computer; the timing is carried out using GPS. In addition to the acquisition system, an infrasound signal detector is installed on the computer. It works in near real-time mode and enables us to find signals and compute their back azimuths. At the end of 2018, a new version of the detector was developed at the Kola Branch GS RAS. The detector began to work much faster, which enabled us to carry out data processing for 2.5 years in two frequency ranges in a short time. The main task of the array is acoustic monitoring, the detection of infrasound events, the determination of their parameters, and the selection of events of natural origin. The data are also used (in combination with the VALR seismic station data) to locate near seismic events, especially weak ones. The analysis of the obtained data revealed the prevailing directions to the signal sources. The change of directions to sources in time was investigated, seasonal features were revealed. Acoustic events were detected in the frequency bands 1–5 Hz and 10–20 Hz, and a significant difference was found in the azimuthal distribution of events for these ranges. A joint analysis of acoustic and seismic data showed that the part of events with both acoustic and seismic components is low – it is almost completely exhausted by career explosions. It was also noted that in addition to explosions in nearby quarries (Kuznechnoye, Pitkäranta) located at a distance of 50–60 km, according to acoustic data, events corresponding to explosions at quarries located at a distance of 100 km or more were repeatedly identified.

scholarly journals Observations of rapid-fire event tremor at Lascar volcano, Chile

1996 ◽  
Vol 39 (2) ◽  
Author(s):  
G. Asch ◽  
K. Wylegalla ◽  
M. Hellweg ◽  
D. Seidl ◽  
H. Rademacher
Keyword(s):  
Fractal Structure ◽  
Seismic Station ◽  
Active Volcano ◽  
Short Term ◽  
Fire Event ◽  
Local Seismicity ◽  
Short Period ◽  
Wide Range ◽  
Lascar Volcano

During the Proyecto de Investigaciòn Sismològica de la Cordillera Occidental (PISCO '94) in the Atacama desert of Northern Chile, a continuously recording broadband seismic station was installed to the NW of the currently active volcano, Lascar. For the month of April, 1994, an additional network of three, short period, three-component stations was deployed around the volcano to help discriminate its seismic signals from other local seismicity. During the deployment, the volcanic activity at Lascar appeared to be limited mainly to the emission of steam and SO2. Tremor from Lascar is a random, «rapid-fire» series of events with a wide range of amplitudes and a quasi-fractal structure. The tremor is generated by an ensemble of independent elementary sources clustered in the volcanic edifice. In the short-term, the excitation of the sources fluctuates strongly, while the long-term power spectrum is very stationary.

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