Sources of primary and secondary microseisms

1994 ◽  
Vol 84 (1) ◽  
pp. 142-148
Author(s):  
Robert K. Cessaro
Keyword(s):  
Seismic Noise ◽  
Low Frequency ◽  
Seismic Array ◽  
Wave Number ◽  
Ocean Bottom ◽  
Wide Angle ◽  
Frequency Wave ◽  
Long Period ◽  
Seismic Records ◽  
Near Shore

Abstract Low-frequency (0.01 to 0.2 Hz) seismic noise, arising from pelagic storms, is commonly observed as microseisms in seismic records from land and ocean bottom detectors. One principal research objective, in the study of microseisms, has been to locate their sources. This article reports on an analysis of primary and secondary microseisms (i.e., near and double the frequency of ocean swell) recorded simultaneously on three land-based long-period arrays (Alaskan Long Period Array, Montana Large Aperture Seismic Array, and Norwegian Seismic Array) during the early 1970s. Reliable microseism source locations are determined by wide-angle triangulation, using the azimuths of approach obtained from frequency-wave number analysis of the records of microseisms propagating across these arrays. Two near-shore sources of both primary and secondary microseisms appear to be persistent in the sense that they are associated with essentially constant near-shore locations. Secondary microseisms are observed to emanate from wide-ranging pelagic locations in addition to the same near-shore locations determined for the primary microseisms.

Prediction and suppression of long-period nonpropagating seismic noise

1973 ◽  
Vol 63 (3) ◽  
pp. 937-958
Author(s):  
Anton Ziolkowski
Keyword(s):  
Transfer Function ◽  
Pressure Distribution ◽  
Noise Level ◽  
Seismic Noise ◽  
Wave Number ◽  
Earth Model ◽  
Noise Power ◽  
Long Period ◽  
Band Limited ◽  
Time Invariant

abstract Approximately half the noise observed by long-period seismometers at LASA is nonpropagating; that is, it is incoherent over distances greater than a few kilometers. However, because it is often strongly coherent with microbarograph data recorded at the same site, a large proportion of it can be predicted by convolving the microbarogram with some transfer function. The reduction in noise level using this technique can be as high as 5 db on the vertical seismometer and higher still on the horizontals. If the source of this noise on the vertical seismogram were predominantly buoyancy, the transfer function would be time-invariant. It is not. Buoyancy on the LASA long-period instruments is quite negligible. The noise is caused by atmospheric deformation of the ground and, since so much of it can be predicted from the output of a single nearby microbarograph, it must be of very local origin. The loading process may be adequately described by the static deformation of a flat-earth model; however, for the expectation of the noise to be finite, it is shown that the wave number spectrum of the pressure distribution must be band-limited. An expression for the expected noise power is derived which agrees very well with observations and predicts the correct attenuation with depth. It is apparent from the form of this expression why it is impossible to obtain a stable transfer function to predict the noise without an array of microbarographs and excessive data processing. The most effective way to suppress this kind of noise is to bury the seismometer: at 150 m the reduction in noise level would be about 10 db.

Modulational Instability and Stationary Waves for the Coupled Generalized Schrödinger-Boussinesq System

2011 ◽  
Vol 66 (3-4) ◽  
pp. 143-150 ◽  
Author(s):  
Zu-Feng Liang
Keyword(s):  
Modulational Instability ◽  
Low Frequency ◽  
Travelling Wave ◽  
Boussinesq System ◽  
Wave Number ◽  
Dispersive Media ◽  
Stationary Waves ◽  
Travelling Wave Solutions ◽  
Frequency Wave ◽  
General Dispersion

The coupled generalized Schr¨odinger-Boussinesq (SB) system, which can describe a highfrequency mode coupled to a low-frequency wave in dispersive media is investigated. First, we study the modulational instability (MI) of the SB system. As a result, the general dispersion relation between the frequency and the wave number of the modulating perturbations is derived, and thus a number of possible MI regions are identified. Then two classes of exact travelling wave solutions are obtained expressed in the general forms. Several explicit examples are presented.

Integrating distributed acoustic sensing, borehole 3C geophone array, and surface seismic array data to identify long-period long-duration seismic events during stimulation of a Marcellus Shale gas reservoir

2019 ◽  
Vol 7 (1) ◽  
pp. SA1-SA10 ◽  
Author(s):  
Payam Kavousi Ghahfarokhi ◽  
Thomas H. Wilson ◽  
Timothy Robert Carr ◽  
Abhash Kumar ◽  
Richard Hammack ◽  
...  
Keyword(s):  
Hydraulic Fracture ◽  
Seismic Data ◽  
Fiber Optic ◽  
Marcellus Shale ◽  
Low Frequency ◽  
Seismic Array ◽  
Long Period ◽  
Long Duration ◽  
Distributed Acoustic Sensing ◽  
Stimulation Of

Microseismic monitoring by downhole geophones, surface seismic, fiber-optic distributed acoustic sensing (DAS), and distributed temperature sensing (DTS) observations were made during the hydraulic fracture stimulation of the MIP-3H well in the Marcellus Shale in northern West Virginia. DAS and DTS data measure the fiber strain and temperature, respectively, along a fiber-optic cable cemented behind the casing of the well. The presence of long-period long-duration (LPLD) events is evaluated in the borehole geophones, DAS data, and surface seismic data of one of the MIP-3H stimulated stages. LPLD events are generally overlooked during the conventional processing of microseismic data, but they represent significant nonbrittle deformation produced during hydraulic fracture stimulation. In a single stage that was examined, 160 preexisting fractures and two faults of suboptimal orientation are noted in the image logs. We identified two low-frequency ([Formula: see text]) events of large temporal duration (tens of seconds) by comparing the surface seismic data, borehole geophone data, and DAS amplitude spectra of one of the MIP-3H stages. Spectrograms of DAS traces in time and depth reveal that the first low-frequency event might be an injection noise that has footprints on all DAS channels above the stimulated stage. However, the surface seismic array indicates an LPLD event concurrent with the first low-frequency event on DAS. The second LPLD event on DAS data and surface seismic data is related to a local deformation and does not have footprints on all DAS channels. The interpreted events have duration less than 100 s with frequencies concentrated below 10 Hz, and are accompanied by microseismic events.

scholarly journals A 3-D spectral-element and frequency-wave number hybrid method for high-resolution seismic array imaging

2014 ◽  
Vol 41 (20) ◽  
pp. 7025-7034 ◽  
Author(s):  
Ping Tong ◽  
Dimitri Komatitsch ◽  
Tai-Lin Tseng ◽  
Shu-Huei Hung ◽  
Chin-Wu Chen ◽  
...  
Keyword(s):  
High Resolution ◽  
Hybrid Method ◽  
Spectral Element ◽  
Seismic Array ◽  
Wave Number ◽  
Frequency Wave ◽  
Array Imaging

Very low frequency Ocean Bottom ambient seismic noise and coupling on the shallow continental shelf

1989 ◽  
Vol 11 (2) ◽  
pp. 129-152 ◽  
Author(s):  
Mark V. Trevorrow ◽  
Tokuo Yamamoto ◽  
Altan Turgut ◽  
Dean Goodman ◽  
Mohsen Badiey
Keyword(s):  
Continental Shelf ◽  
Seismic Noise ◽  
Low Frequency ◽  
Ambient Seismic Noise ◽  
Ocean Bottom ◽  
Very Low Frequency

scholarly journals BEACH FORESHORE RESPONSE TO LONG-PERIOD WAVES

1984 ◽  
Vol 1 (19) ◽  
pp. 132 ◽  
Author(s):  
P.A. Howd ◽  
R.A. Holman
Keyword(s):  
Time Series ◽  
Low Frequency ◽  
Time Lapse ◽  
Mean Square ◽  
Erosion And Deposition ◽  
Frequency Wave ◽  
Long Period ◽  
Typical Time ◽  
The Waves ◽  
Time Lapse Photography

A field experiment has been carried out to test the hypothesis that infragravity and lower frequency waves influence patterns of erosion and deposition on the beach foreshore. The data show coherent fluctuations in the foreshore sediment level which can be related to low frequency wave motions. The fluctuations have heights of up to 6 cm with typical time scales of 8 to 10 minute periods. They can be characterized in two ways: by the progression of the fluctuation up the foreshore slope (landward), and by the decrease in the root-mean-square (RMS) height of the fluctuations as they progress landward. Analysis of runup time series obtained by time-lapse photography concurrent with the sediment level measurements reveals long-period waves of undetermined origin which are positively correlated with the sediment level fluctuations. This strongly suggests that the waves are responsible for forcing the sediment level fluctuations.

Sign in / Sign up

Export Citation Format

Share Document