Digitization of the Carnegie Analog Broadband Instruments Tape Records (1965–1996)

2020 ◽  
Vol 91 (3) ◽  
pp. 1441-1451
Author(s):  
Steven Golden ◽  
Lara S. Wagner ◽  
Brian Schleigh ◽  
Daniela Power ◽  
Diana C. Roman ◽  
...  
Keyword(s):  
Seismic Data ◽  
Force Feedback ◽  
Dynamic Range ◽  
Good Condition ◽  
Digital Recording ◽  
Carnegie Institution ◽  
Ongoing Effort ◽  
Recorded Data ◽  
The 1960S ◽  
Scientific Value

Abstract Between 1965 and 2003, the Carnegie Institution of Washington’s Department of Terrestrial Magnetism operated a continuous network of nine broadband seismographs with locations in South America, Japan, Iceland, Papua New Guinea, and Washington, D.C. The Carnegie seismographs designed in the 1960s by Selwyn Sacks were among the earliest broadband instruments, sensing between at least 30 s and ∼30  Hz. Given the scarcity of historic seismic data of comparable bandwidth and dynamic range prior to the widespread shift to force-feedback instruments and digital recording around the mid-1980s, this dataset is still of high scientific value today. The Carnegie seismographs recorded data to magnetic tapes meant to be read and analyzed using a custom playback system. Since 1989 these tapes have been stored in a climate-controlled, electromagnetically shielded room, which preserved them in reasonably good condition. However, some tapes now show signs of moisture damage, and reading them is difficult and time consuming by today’s standards, creating a barrier to the use of this dataset. To overcome these issues, we have undertaken an ongoing effort to digitize this dataset with the goal of making it publicly available in Standard for the Exchange of Earthquake Data (SEED) format at the Incorporated Research Institutions for Seismology Data Management Center (IRIS DMC).

Near-Borehole Imaging Using Full-Waveform Sonic Data

2021 ◽  
Author(s):  
Hala Alqatari ◽  
Thierry-Laurent Tonellot ◽  
Mohammed Mubarak
Keyword(s):  
Seismic Data ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Full Waveform ◽  
Time Migration ◽  
Imaging Results ◽  
High Resolution Images ◽  
Recorded Data ◽  
The Impact ◽  
Processing Steps

Abstract This work presents a full waveform sonic (FWS) dataset processing to generate high-resolution images of the near-borehole area. The dataset was acquired in a nearly horizontal well over a distance of 5400 feet. Multiple formation boundaries can be identified on the final image and tracked at up to 200 feet deep, along the wellbore's trajectory. We first present a new preprocessing sequence to prepare the sonic data for imaging. This sequence leverages denoising algorithms used in conventional surface seismic data processing to remove unwanted components of the recorded data that could harm the imaging results. We then apply a reverse time migration algorithm to the data at different processing stages to assess the impact of the main processing steps on the final image.

scholarly journals Mechanical Frequency Tuning by Sensory Hair Cells, the Receptors and Amplifiers of the Inner Ear

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Pascal Martin ◽  
A.J. Hudspeth
Keyword(s):  
Hopf Bifurcation ◽  
Hair Cells ◽  
Force Feedback ◽  
Dynamic Range ◽  
Frequency Tuning ◽  
Hair Bundle ◽  
Annual Review ◽  
Publication Date ◽  
Mechanical Waves ◽  
Myosin Motors

We recognize sounds by analyzing their frequency content. Different frequency components evoke distinct mechanical waves that each travel within the hearing organ, or cochlea, to a frequency-specific place. These signals are detected by hair cells, the ear's sensory receptors, in response to vibrations of mechanically sensitive antennas termed hair bundles. An active process enhances the sensitivity, sharpens the frequency tuning, and broadens the dynamic range of hair cells through several mechanisms, including active hair-bundle motility. A dynamic interplay between negative stiffness mediated by ion channels’ gating forces and delayed force feedback owing to myosin motors and channel reclosure by calcium ions brings the hair bundle to the vicinity of an oscillatory instability—a Hopf bifurcation. Operation near a Hopf bifurcation provides nonlinear generic features that are characteristic of hearing. Multiple gradients at molecular, cellular, and supercellular scales tune hair cells to characteristic frequencies that cover our auditory range. Expected final online publication date for the Annual Review of Condensed Matter Physics, Volume 12 is March 10, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Processing, inversion, and interpretation of a 2D seismic data set from the North Viking Graben, North Sea

Geophysics ◽  
2003 ◽  
Vol 68 (3) ◽  
pp. 837-848 ◽  
Author(s):  
Gislain B. Madiba ◽  
George A. McMechan
Keyword(s):  
Seismic Data ◽  
Dynamic Range ◽  
Velocity Ratio ◽  
Total Porosity ◽  
Shear Velocity ◽  
Seismic Section ◽  
Data Set ◽  
Amplitude Variation With Offset ◽  
Fluid Content ◽  
The North

Simultaneous elastic impedance inversion is performed on the 2D North Viking Graben seismic data set used at the 1994 SEG workshop on amplitude variation with offset and inversion. P‐velocity (Vp), S‐velocity (Vs), density logs, and seismic data are input to the inversion. The inverted P‐impedance and S‐impedance sections are used to generate an approximate compressional‐to‐shear velocity ratio (Vp/Vs) section which, in turn, is used along with water‐filled porosity (Swv) derived from the logs from two wells, to generate fluid estimate sections. This is possible as the reservoir sands have fairly constant total porosity of approximately 28 ± 4%, so the hydrocarbon filled porosity is the total porosity minus the water‐filled porosity. To enhance the separation of lithologies and of fluid content, we map Vp/Vs into Swv using an empirical crossplot‐derived relation. This mapping expands the dynamic range of the low end of the Vp/Vs values. The different lithologies and fluids are generally well separated in the Vp/Vs–Swv domain. Potential hydrocarbon reservoirs (as calibrated by the well data) are identified throughout the seismic section and are consistent with the fluid content estimations obtained from alternative computations. The Vp/Vs–Swv plane still does not produce unique interpretation in many situations. However, the critical distinction, which is between hydrocarbon‐bearing sands and all other geologic/reservoir configurations, is defined. Swv ≤ 0.17 and Vp/Vs ≤ 1.8 are the criteria that delineate potential reservoirs in this area, with decreasing Swv indicating a higher gas/oil ratio, and decreasing Vp/Vs indicating a higher sand/shale ratio. As these criteria are locally calibrated, they appear to be valid locally; they should not be applied to other data sets, which may exhibit significantly different relationships. However, the overall procedure should be generally applicable.

Report on Archives of the Popular and Revolutionary Republic of Guinea in Conakry

1981 ◽  
Vol 8 ◽  
pp. 333-334
Author(s):  
Martin A. Klein
Keyword(s):  
Classification System ◽  
Original Work ◽  
Good Condition ◽  
Colonial Administration ◽  
Poor Condition ◽  
Republic Of Guinea ◽  
Exposed Point ◽  
Pleasant Surprise ◽  
Set Up ◽  
The 1960S

Before I came to Conakry I had been warned that the archives were in poor condition, had suffered damage from the elements and from the termites, and were not well maintained. One scholar who worked here in the 1960s spoke not only of termite damage but of chickens and goats wandering through. To my pleasant surprise I have found that the archives are fairly extensive, that they are in relatively good condition, and that they are being maintained as well as can be expected. The locale is not an ideal one, though its location on an exposed point of land near the sea makes for pleasant breezes and good cross-ventilation. There is no control of either temperature or humidity in the building. While some dossiers are partially damaged, I have not seen one that is not usable. My biggest problem has been the handwriting of the clerks and administrators who made copies of correspondence in local registers.The original work of organizing the archives was done by Madeira Keita, the R.D.A. leader, who worked here during the early 1950s. The classification system he set up was maintained by Damien d'Almeida, who published a repertoire in 1962. The repertoire is fairly detailed and it notes when a dossier or a register is in poor condition. The classification system is sound, though occasionally one finds documents, reports, and correspondance grouped together in a haphazard manner. The problem was more the sloppy recordkeeping of the colonial administration than the work of the undermanned archivists. In general, I have been to find what I have wanted and the organization has been very useful. The present archivist, Moctar Ba, is competent and seems conscientious.

scholarly journals Radar Studies of Internal Layers and Bottom Topography at Dome C, East Antarctica (Abstract only)

1982 ◽  
Vol 3 ◽  
pp. 341-341
Author(s):  
Kenneth C. Jezek ◽  
Sion Shabtaie ◽  
Charles R. Bentley
Keyword(s):  
Bottom Topography ◽  
Rough Terrain ◽  
Digital Recording ◽  
Internal Layers ◽  
Abrupt Decrease ◽  
University Of Wisconsin ◽  
South West ◽  
Recorded Data ◽  
The University ◽  
Local Map

Extensive and detailed radar surveys at Dome C were conducted during the 1978–79 and 1979–80 austral field seasons by groups from the University of Wisconsin. Measurements were conducted within a 10 × 10 km grid centered approximately on the Dome C camp (some additional studies were carried out as far as 20 km from the camp) and involved profiling of internal layers and bottom topography. In addition, a new digital recording system for the radar was used during the first season and has yielded interesting results on internal layers near the French bore hole.Analysis of these data has produced a local map of bottom topography showing generally rough terrain. In particular, there is a rapid deepening of the bottom topography (about 500 m over 2 km) just grid south-west of the camp. Internal layers were found to be discontinuous on a scale of tens of meters. The deepest internal layers were detected at depths of about 2 500 m although a set of remarkable layer-like returns were observed about 50 to 100 m above the interpreted base of the ice. (It is not yet clear whether these returns represent reflections from layers internal to the ice or whether they are reflections and diffractions associated with the rough terrain.) In addition the processed digital records show an abrupt decrease in the reflection strength of internal layers at about 1 700 m. Because the digitally recorded data were collected at only one site, we reserve concluding that this observation is characteristic of the entire Dome C area until more of the photographically recorded data can be reduced.

Data- and model-domain up/down wave separation for reverse-time migration with free-surface multiples

2020 ◽  
Vol 223 (1) ◽  
pp. 77-93
Author(s):  
Peng Guo ◽  
Huimin Guan ◽  
George A McMechan
Keyword(s):  
Wave Equation ◽  
Free Surface ◽  
Seismic Data ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Wave Separation ◽  
Time Migration ◽  
Model Domain ◽  
Image Artefacts ◽  
Recorded Data

SUMMARY Seismic data recorded using a marine acquisition geometry contain both upgoing reflections from subsurface structures and downgoing ghost waves reflected back from the free surface. In addition to the ambiguity of propagation directions in the data, using the two-way wave equation for wavefield extrapolation of seismic imaging generates backscattered/turned waves when there are strong velocity contrasts/gradients in the model, which further increases the wavefield complexity. For reverse-time migration (RTM) of free-surface multiples, apart from unwanted crosstalk between inconsistent orders of reflections, image artefacts can also be formed along with the true reflector images from the overlapping of up/downgoing waves in the data and in the extrapolated wavefield. We present a wave-equation-based, hybrid (data- and model-domain) wave separation workflow, with vector seismic data containing pressure- and vertical-component particle velocity from dual-sensor seismic acquisition, for removing image artefacts produced by the mixture of up/downgoing waves. For imaging with free-surface multiples, the wavefield extrapolated from downgoing ghost events (reflected from the free surface) in the recorded data act as an effective source wavefield for one-order-higher free-surface multiples. Therefore, only the downgoing waves in the data should be used as the source wavefield for RTM with multiples; the recorded upgoing waves in the seismograms will be used for extrapolation of the time-reversed receiver wavefield. We use finite-difference (FD) injection for up/down separation in the data domain, to extrapolate the down- and upgoing waves of the common-source gathers for source and receiver wavefield propagation, respectively. The model-domain separation decomposes the extrapolated wavefield into upgoing (backscattered) and downgoing (transmitted) components at each subsurface grid location, to remove false images produced by cross-correlating backscattered waves along unphysical paths. We combine FD injection with the model-domain wavefield separation, for separating the wavefield into up- and downgoing components for the recorded data and for the extrapolated wavefields. Numerical examples using a simple model, and the Sigsbee 2B model, demonstrate that the hybrid up/down separation approach can effectively produce seismic images of free-surface multiples with better resolution and fewer artefacts.

RECOMMENDED STANDARDS FOR DIGITAL TAPE FORMATS

Geophysics ◽  
1972 ◽  
Vol 37 (1) ◽  
pp. 36-44 ◽  
Author(s):  
E. P. Meiners ◽  
L. L. Lenz ◽  
A. E. Dalby ◽  
J. M. Hornsby
Keyword(s):  
Seismic Data ◽  
Digital Recording ◽  
Field Recording ◽  
Work Done

This paper is the result of work done by a subcommittee of the SEG Committee on Digital Recording Standards. It recommends an additional tape format for 9‐track field recording of seismic data and an optional use of 1600 bpi, as well as 800 bpi, for all field formats.

The Seismic Research Observatory

1976 ◽  
Vol 66 (6) ◽  
pp. 2049-2068 ◽  
Author(s):  
Jon Peterson ◽  
Howell M. Butler ◽  
L. Gary Holcomb ◽  
Charles R. Hutt
Keyword(s):  
Seismic Data ◽  
Broad Band ◽  
Computer Processing ◽  
Preliminary Evaluation ◽  
Digital Recording ◽  
Digital Form ◽  
Data Resource ◽  
Long Period ◽  
Period Data ◽  
Mass Position

abstract Thirteen advanced seismograph systems, called Seismic Research Observatories (SRO), are being installed as part of a program to upgrade the worldwide seismic data network. The SRO system was created by combining a recently developed broad-band borehole seismometer and a software-controlled recording system. The seismometers are being installed at a depth of 100 meters to avoid wind-generated noise in the long-period band. A seismometer output that is flat in acceleration between periods of 1 and 50 sec is used to produce both short- and long-period data that are recorded on analog drum recorders and in digital form on magnetic tape. Very-long-period data, obtained from the seismometer mass position output, can be recorded as well. Digital recording of gain-ranged data provides an amplitude of nearly 120 dB. Preliminary evaluation of the SRO data system indicates that major design objectives have been met. The network of SRO stations will be an important new data resource for seismological investigations, especially for those studies that require computer processing of the data.

scholarly journals Radar Studies of Internal Layers and Bottom Topography at Dome C, East Antarctica (Abstract only)

1982 ◽  
Vol 3 ◽  
pp. 341
Author(s):  
Kenneth C. Jezek ◽  
Sion Shabtaie ◽  
Charles R. Bentley
Keyword(s):  
Bottom Topography ◽  
Rough Terrain ◽  
Digital Recording ◽  
Internal Layers ◽  
Abrupt Decrease ◽  
University Of Wisconsin ◽  
South West ◽  
Recorded Data ◽  
The University ◽  
Local Map

Extensive and detailed radar surveys at Dome C were conducted during the 1978–79 and 1979–80 austral field seasons by groups from the University of Wisconsin. Measurements were conducted within a 10 × 10 km grid centered approximately on the Dome C camp (some additional studies were carried out as far as 20 km from the camp) and involved profiling of internal layers and bottom topography. In addition, a new digital recording system for the radar was used during the first season and has yielded interesting results on internal layers near the French bore hole. Analysis of these data has produced a local map of bottom topography showing generally rough terrain. In particular, there is a rapid deepening of the bottom topography (about 500 m over 2 km) just grid south-west of the camp. Internal layers were found to be discontinuous on a scale of tens of meters. The deepest internal layers were detected at depths of about 2 500 m although a set of remarkable layer-like returns were observed about 50 to 100 m above the interpreted base of the ice. (It is not yet clear whether these returns represent reflections from layers internal to the ice or whether they are reflections and diffractions associated with the rough terrain.) In addition the processed digital records show an abrupt decrease in the reflection strength of internal layers at about 1 700 m. Because the digitally recorded data were collected at only one site, we reserve concluding that this observation is characteristic of the entire Dome C area until more of the photographically recorded data can be reduced.

scholarly journals THE USE OF EDUCATIONAL SEISMOGRAPHS IN THE SEISMOLOGY SCHOOL NETWORK “EGELADOS”

2017 ◽  
Vol 43 (2) ◽  
pp. 989
Author(s):  
G. Fermeli ◽  
T. Vitsas ◽  
P. Foundas ◽  
E. Sokos ◽  
S. Alexandropoulou ◽  
...  
Keyword(s):  
School Level ◽  
Digital Recording ◽  
National Observatory ◽  
High School Level ◽  
Short Period ◽  
Teachers And Students ◽  
School Network ◽  
Recorded Data ◽  
Basic Concepts ◽  
And Mathematics

In this paper we attempt to describe the experience we gained, working with a specially designed seismograph as an educational device. It is a modern instrument with short period response, GPS timing and digital recording on personal computer. The installation was done in the frame of the local seismology school network, called “Egelados”. The knowledge of basic concepts of geology, physics and mathematics (Lower High School level - Gymnasium) is a prerequisite for the use of the instrument. Further research of the earthquake phenomenon and the analysis of the recorded data leads to didactic objectives in sciences and mathematics which are included in the Lyceum curriculum. The reliability test of the results obtained using the seismograph has, from the analysis students made, shown up to now declinations of the events magnitude of 0,2 - 0,4 when compared to magnitudes published by National Observatory of Athens-Institute of Geodynamics. Students’ constructions to overcome the calculation difficulties to find the exact location of epicentre are often proposed activating in this way their research mood. Up to now the use of the tool, in the framework of network “Egelados”, not only connects the participating schools but also gives the opportunity for further collaboration among teachers and students that have installed a similar instrument. Finally, everyday use of the seismograph reveals its drawbacks and provides ideas of enhancements.

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