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An optical fiber infrasound sensor (OFIS) is a long compliant tube wrapped with two optical fibers that integrate pressure variation along the length of the tube at the speed of light via laser interferometry. Here we only present the initial results of research conducted under this contract due to delays in the construction of the Camp Elliott OFIS array. All the field work has been completed, but the remainder of the data analysis will be completed in the next two months and presented in the associated poster. In this paper, we show that M-sequences transmitted via an array of 18-inch subwoofers comprise a portable infrasound sensor calibrator, which also permits in situ evaluation of wind noise reduction filters. For example, a comparison of a 60-m OFIS with a Bruel & Kjaer (B&K) microphone at a signal frequency of 50 Hz for a source ~240 m away shows that the OFIS reduced wind and other types of undesirable noise by 18 dB over the B&K microphone with a standard sponge wind screen. An 8-subwoofer array at a range of ~240 m yields a reliable calibration signal that smoothly decreases in power by a rate of 2.5 dB/Hz with decreasing frequency to 8 Hz, which is fairly remarkable given the 20 Hz rolloff frequency of the amplifier and speakers., Presented at Proceedings of the Monitoring Research Review (30th): Ground-Based Nuclear Explosion Monitoring Technologies, held at Portsmouth, VA on 23-25 Sep 2008. Published in Proceedings of the Monitoring Research Review (30th): Ground-Based Nuclear Explosion Monitoring Technologies, p902-911, 2008. The original document contains color images. Proposal no. BAA06-41.

We compute and analyze P-wave spectra from 18,101 earthquakes and 1770 explosions recorded by 196 broadband seismic stations in southern California at epicentral distances up to 100 km. We use an online waveform database stored on a RAID system at Caltech, which provides complete access to the Southern California Seismic Network (SCSN) seismogram archive. We compute spectra using 1.28s noise and signal windows, positioned immediately before and after the P arrivals. After applying a signal-to-noise cutoff, we process the spectra using an iterative robust least-squares method to isolate source, receiver, and propagation path contributions. This corrects for first-order attenuation structure, as well as near-receiver site effects and any errors in the instrument response functions. Using the earthquake spectra and a simple source model, we compute an empirical Green s function to remove the tradeoff between the source terms and other terms in our model. Our observed earthquake spectra are fit reasonably well with a constant stress drop model over a wide range of moment. However, the explosion spectra show significant differences from the earthquake spectra and have generally steeper falloffs at high frequencies. We also compare P and S-wave amplitudes and find modestly smaller average S amplitudes for the explosions compared to the earthquakes. The best earthquake/explosion discriminant is the RMS misfit to an omega-2 source model, which works for ~90% of the events., The original document contains color images.

The long-term goal of this research is to develop and test predictive models for nearshore processes. This is to be accomplished within the framework of the nearshore as a hierarchical complex system, wherein, at discretely ordered space and time scales, a small number of variables emerge as the dominant influences on the dynamics of this nonlinear, open system and the interactions between these dominant variables give rise to complex, emergent behavior., The original document contains color images. All DTIC reproductions will be in black and white.

The long-term goal of this research is to develop and test predictive models for nearshore processes. Initial development and testing of models is to be accomplished through monitoring over a broad range of spatial (both horizontal and vertical) and temporal scales. Model development takes place within the framework of the nearshore as a hierarchical complex system, wherein, at discretely ordered space and time scales, a small number of variables emerge as the dominant influences on the dynamics of this nonlinear, open system and the interactions between these variables give rise to complex, emergent behavior. The specific objectives of this research project are (i) to identify the dominant variables and processes operative in the nearshore; (ii) to formulate and develop predictive, hierarchical complex systems models for nearshore processes and features, including sand bars, megaripples, breaking waves, infragravity wave generation, surf zone currents, and swash zone flow and morphology; (iii) to monitor (on time scales ranging from seconds to years and spatial scales ranging from meters to a kilometer) nearshore bathymetric, volumetric and hydrodynamical patterns; (iv) to relate complex systems models to measurements acquired through remote sensing; and (v) to propose and design new field experiments capable of refuting complex systems and competing models.

Global surface wave arrival angles (also called polarization data) are extremely useful data to constrain the short wavelength structure in global surface wave phase velocity maps. This paper investigates the feasibility of using such data on a more regional scale to validate regional models. We measure the arrival angles at the Saudi Arabian Seismic Network and compare them with predictions calculated using published phase velocity maps. We find large discrepancies between data and existing maps and demonstrate the great potential such data have to constrain the regional structure around the Saudi Arabian Peninsula. A by-product of our procedure is the retrieval of the misalignment of the horizontal components of the seismic sensor. We find a significant misalignment of approximately 4 degrees for the seismometer at station AFIF., Presented at the Annual DoD/DOE Seismic Research Symposium: Planning for Verification of and Compliance with the Comprehensive Nuclear-Test-Ban Treaty (22nd) held in New Orleans, LA on 13-15 September 2000. Published in the proceedings of the same.

We have conducted a preliminary analysis of kiloton class, anomalous, mining blasts in Wyoming using IMS seismic data. This research has begun on two fronts. We are examining well documented mine blasts in the Powder River Basin trend in Wyoming using the Pinedale seismic array (PDAR) and the single station ULM. These data are being used with near-regional video, seismic and acoustic data collected by UCSD, LANL, SMU and AFTAC during field experiments in 1996 and 1997. These data are being used to examine differences in the waveforms of mining blasts that are essentially co-located, and detonated with similar planned blasting grids, but for which some have included a significant detonation anomaly (otherwise known as a sympathetic detonation). We are examining coherent and incoherent beams of Pinedale array data in an attempt to detect the large detonations. We are using physical modeling in an attempt to reproduce the waveforms of the anomalous blasts. Our main goal with the modeling is to estimate the explosive yield and timing of the detonation anomalies. Kiloton class mine blasts are not uncommon in numerous regions worldwide such as Wyoming, Kentucky and, at least historically, the Kuzbass mining region in Russia. Recordings of large blasts in the Kuzbass mining region exhibit time- and frequency-domain characteristics below 10 Hz that are similar to those observed in the Wyoming events. In specific, these features include enhanced surface waves and spectral modulations. We tentatively conclude that the discrimination methods we have found to be useful in Wyoming can also be used in this region. In collaboration with Vitaly Khalturin (LDEO) we are seeking ground truth information on large mining blasts in the Altay-Sayan mining region. This exploratory phase will be followed by physical modeling of the events for which we are able to secure adequate ground truth information., Published in Proceedings of the Annual DoD/DOE Seismic Research Symposium: Planning for Verification of and Compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) (22nd), held in New Orleans, LA on 13-15 Sep 2000. U.S. Government or Federal Rights. The original document contains color images.

The infrasound element of the global International Monitoring System (IMS) will consist of 60 stations. Each station in the global network will consist of an array of sensors. As the local surface wind strongly influences ambient infrasonic noise levels in the band of interest to the nuclear treaty monitoring community (between 0.05 and 4 Hz), each of these sensors will include a spatial filter designed to reduce the effects of wind noise. There are, however, many different design suggestions for spatial filtering system. In order to maximize the signal-to-noise ratio of signals of interest, it is essential that the spatial noise reduction systems be optimized to provide the most significant noise power reduction over the broadest band possible. We believe that substantial progress in these areas requires the comparative testing of the major noise reducing systems exposed to the same meteorological conditions. Under our new DTRA contract we will construct and test several spatial filtering systems by simultaneous operation at the Pinon Flat Observatory (PFO) in southern California. These systems include the wind fence, microporous pipes, and a recent design in which a large number of open ports are connected to a summing manifold, and then to the microbarometer, by solid pipes. We will also compare these mechanical noise suppression schemes with a new design based on light-speed pressure averaging via optical fibres. The observatory is an ideal test site as it is subjected to winds that come from all azimuths at speeds ranging from 0 to over 10 m/s., Proceedings of the 22nd Annual DoD/DOE Seismic Research Symposium: Planning for Verification of and Compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) held in New Orleans, Louisiana on September 13-15, 2000, U.S. Government or Federal Rights.. The original document contains color images.

The long-term goal of this research is to develop and test predictive models for nearshore and coastal processes. Initial development and testing of models is to be accomplished through monitoring over a broad range of spatial and temporal scales. Model development is to be accomplished within the framework of the nearshore as a hierarchical complex system, wherein, at discretely ordered space and time scales, a small number of variables emerge as the dominant influences on the dynamics of this nonlinear, open system and the interactions between these dominant variables give rise to complex, emergent behavior., See also ADM002252. The original document contains color images.

The long term goal of my research is directed toward understanding wave generation and wave motion in the ocean and in laboratory simulations thereof. The prmary approach is through mathematical models. Solutions ultimately are developed in both analytical and numerical form, but the goal is to obtain analytical results that inform phenomenological models for the prediction of physical events.

In studies of low-frequency reverberation within the marine environment, a central concern is the relationship between reverberation events and morphological features of the seafloor. A time-domain migration algorithm for the reverberation intensity field is developed that produces scattering coefficient maps coregistered with a bathymetry database. The algorithm is tailored to broadband transient sources with good range resolution, and was developed to analyze an extensive set of reverberation records from a 200-255 Hz source collected on the flanks of the Mid-Atlantic Ridge. The precise, sample-by-sample, tracking of wavefronts across elements 9f the bathymetry database that forms the foundation of the algorithms implementation, results in reverberation maps that show a clear and detailed correlation between scattering and morphology, with narrow scarp slopes consistently high- lighted. Environmentally induced asymmetries in transmission loss and incidence angle are exploited to break the inherent left-right ambiguity of the receiver array. Iterative migration, assuming a dominant dependence of backscatter on grazing angle, produces images, even from individual records, that show good ambiguity resolution. Results from multiple records corroborate the effectiveness of the ambiguity resolution and demonstrate the stability of the scattering coefficient estimates and the acoustic system.

In studies of low-frequency reverberation within the marine environment, a central concern is the relationship between reverberation events and morphological features of the seafloor. A time-domain migration algorithm for the reverberation intensity field is developed that produces scattering coefficient maps coregistered with a bathymetry database. The algorithm is tailored to broadband transient sources with good range resolution, and was developed to analyze an extensive set of reverberation records from a 200-255 Hz source collected on the flanks of the Mid-Atlantic ridge. The precise, sample-by-sample, tracking of wavefronts across elements of the bathymetry database that forms the foundation of the algorithms implementation, results in reverberation maps that show a clear and detailed correlation between scattering and morphology, with narrow scarp slopes consistently highlighted.

The CTBT negotiations have endowed small seismo/acoustic events (mb ^ 2.5) with a much greater significance than they have had in the past and have increased the need for automated regional discrimination. We have been contracted by AFTAC to develop a small event discriminant that uses a time frequency expansion (sonogram) of seismic coda to discriminate ripple fired mining explosions from single explosions and earthquakes. The Automated Time Frequency Discriminant (ATFD) which we have developed uses a binary sonogram which is derived from the original, spectral, sonogram by the application of filters which replace the spectral information with a binary code which simply reflects local spectral highs and lows. We have found that the binary patterns which we extract from the coda of ripple-fired events are banded and thus distinct from those obtained from single explosions and earthquakes. The bands, which result from source finiteness, intershot delays or a combination of the two, are largely independent of time and of the recording component. The ATFD uses three statistical tests to measure the time and recording component independence and automatically recognize these bands. All of the raw discrimination parameters produced by these tests are merged into a single discriminant score with multivariate statistics.

The four most widely accepted forms used to represent the source time history of a nuclear explosion have been unified into a single simple time domain expression. A unique feature of this expression is that the Mueller-Murphy representation is given in terms of two characteristic frequency parameters (k's) and two independent source shaping parameters (B's). The Haskell, Helmberger-Hadley and von Seggern-Blandford representations have always been specified by one of each. There are a total of ten free parameters in the generalized fitting function which are too many for fitting any one type of seismic observation. Yet, they may be useful for unifying different types of data. In particular the Mueller-Murphy parameters are useful for modeling cavity scaling observations and the Helmberger-Hadley are best for studies of near field seismograms. However, there is a clear need to relate the investigations of both types of information. No unique mathematical relationship between the ten free parameters exists, but the differences between the pulses they predict can be measured in a least squares sense. To accomplish this, we have assumed that the Mueller-Murphy source is in fact correct and have found those source functions of the other three representations which approximate it most closely. An important result is that each of the four realizations of the unified source representation can be related to the others in a meaningful way, and the differences are negligible in a least squares sense. Future work needs to be directed at unifying the scaling laws of each representation which is where the real physics lies.

We are developing a radically new approach to the problem of low signal-to-noise long-period surface waves using a newly developed approach that Thomson (1990) calls quadratic inverse theory. Analysis of surface wave dispersion requires precise measurements of relative phase. The double coherence estimate provides the the coherence and phase between different frequencies in the same signal. We tested the multitaper double-coherence technique with simple signals. The signals were designed to mimic the characteristics of idealized seismic data (both surface and body waves) but with defined frequency and amplitude. Initially, pure signals were processed and plotted. The signals were then degraded by adding random noise and plotted. We compared the results from the pure signals and the noisy signals to identify robust features in the coherence plots. Tests with real seismic data yield patterns similar to those seen in synthetic tests. We plan to conduct further tests with seismic data and investigate methods to further improve signal resolution., This article is from 'Proceedings of the Annual Seismic Research Symposium on Monitoring a Comprehensive Test Ban Treaty (17th) Held in Scottsdale, Arizona on 12-15 September, 1995', 1996 0607 035, p807-814.

The fundamental goal of the research performed under this contract has been to determine the precision with which the ocean mesoscale sound speed field can be measured using acoustic techniques. The basic idea is straightforward: to use acoustic sources and/or receivers suspended from ships to provide dense sets of acoustic ray paths in order to construct sound speed maps with mesoscale resolution over large areas. We named the technique Moving Ship Tomography. Determining the fraction of ocean sound speed variance that can be measured using acoustic techniques is of critical importance in potential applications to passive and active ASW systems. The ocean sound speed field is required as input for matched field (and other) processing of long range acoustic transmissions. The ability to measure the ocean sound speed (temperature) field with mesoscale resolution is also important to the study of eddy kinematics and dynamics, to verify numerical models, and to study data assimilation techniques.

Chandrasekhar's derivation, from energy considerations, of the sufficient condition R > 1/4 for stability of a stratified shear flow, in which R is the local Richardson number, is amended to obtain R > 1, in agreement with the earlier arguments. (Reprints).

The small, finite amplitude response of a damped, internally resonant double pendulum subject to parametric excitation at four times the frequency of the dominant pendulum is shown to exhibit chaotic behavoir for certain values of frequency offset and dissipation. This is in contrast to Miles, where the driving frequency approximated twice that of the dominant pendulum, and regular motion was found to exist for all values of frequency offset and dissipation., See also AD-A160 859. Summary in German.

Seismographic stations were operated for several months during 1987 at 3 sites within 250 km of the Kazakh Test Site in the USSR and through most of 1988 and early 1989 at 3 sites within 250 km of the Nevada Test Site. The Soviet sites included Karkaralinsk, Bayanaul, and Karasu, and the US stations were located at Nelson, NV, Deep Springs, CA, and Troy Canyon, NV. All 6 stations were equipped with high-frequency, three-component surface (1-80 Hz) and borehole (.2-80 Hz) instruments. We have analyzed nearly 2,000 recordings of ambient ground noise collected at the US stations and have systematically reexamined several hundred noise measurements from the USSR sites to compare surface and borehole noise levels among the 6 locations. Wind speed was recorded during most of the deployment at each site, making possible a comparison of noise levels at each station as a function of wind speed. The operational periods yielded data covering a reasonable sampling of meteorological conditions, although the overall duration of occupation of each site was too short to permit a reliable characterization of seasonal noise variations. Conclusions include: (1) In general, noise levels in the boreholes were affected by wind conditions to a much smaller degree than were the surface emplacements. (2) Wind did not become a noticeable source of noise at the surface emplacements until a minimum wind speed was reached (typically 4 to 5 m/sec). (edc)

A field test of ocean acoustic tomography was conducted for 2 months in 1981 in a 300 km square at 26 deg N, 70 deg W in the North Atlantic. From measured travel times between moorings, various displays of the three-dimensional field of sound speed (closely related to temperature) were obtained by inversion procedures. These procedures use historical ocean data as a reference, but all information from the in situ surveys has been withheld; the 'pure' tomographic results were then compared to direct in situ observations. The tomographically derived spatial mean profile compares favorably to an equivalent profile from the in situ observations; both differ significantly from the historical average. Maps constructed at three day intervals for a two month period show a pattern of eddy structure in agreement with the direct observations within computed mapping errors, but these mapping errors are too large for many oceanographic purposes. The mapping errors are the result of an unexpectedly large noise variance in travel time. The 1981 tomographic results strongly suggest that the ocean sometimes undergoes transitions too rapid to be mapped over such large areas by shipboard observations.

It is shown that the evolution equations for a triad of weakly damped, resonantly interacting waves are isomorphic to the corresponding equations for undamped waves (and therefore may be integrated in terms of elliptic functions) if the damping coefficient is the same for each member of the triad. This condition is satisfied for topographic Rossby waves for which dissipation is through a turbulent Ekman layer and the wavelengths are small compared with the Rossby radius of deformation.

The problem of obtaining the solid earth's response to tidal forces is outlined in this extract from Tim Whorf's thesis. The thesis treats the problem of searching for a non-Newtonian gravitational effect in earth tides which is due to a fixed universal reference frame (The PPN effect).

Due to the presence of the ocean sound channel, in general many ray paths (multipaths) connect a given acoustic source-receiver pair in the ocean. The number and structure of the multipaths depend on the details of the sound channel and the positions of the source and receiver. As each multipath samples the ocean differently each contains unique information about the sound speed structure of the ocean. In order to exploit this information one must first identify each of the measured multipath arrivals. Here the author addresses the related problems of identifying multipath arrivals and the subsequent inversion of this data for the ocean structure. (Author), This article is from the PAME Proceedings, Pattern Analysis in the Marine Environment, an Ocean Science and Technology Workshop Held at the Naval Ocean Research and Development Activity, NSTL, MS. on 24-26 Mar 82, AD-A140 195, p189-197.

The titles of 50 papers reporting research are listed and subdivided into the following categories: applied mathematics, diffraction and radiation, Hamiltonian methods, Korteweg-deVries equation, nonlinear dynamics, nonlinear waves, solitary waves, stability, wave damping, and miscellaneous.

The overall purpose of this project was to study ocean dynamics along the Aleutian Island chain, which is the boundary between the North Pacific Ocean and the Bering Sea. These two bodies of water communicate through a number of straits (usually called passes) which are shallowest at the eastern end (a list is given in Favorite, 1967). The specific goal of this project was to use pre-existing data sets, particularly long time series of sea level and meteorology, to understand something of the physical oceanography of the area. Particular questions of interest included: Tidal dynamics: how do the tides propagate along the chain and through the passes? Why is there an anomalously small S2 tide in the Bering Sea? What is the flux of tidal energy into the Bering Sea, and how is it distributed along the chain? Other sea level variations: how does atmospheric forcing affect low-frequency sea level changes? Are other low-frequency signals present that could be correlated with shelf waves or with changes in currents such as the Alaskan Stream (Favorite et al., 1976) near the island chain? Is there any nonlinear interaction between tides and sea level? Can any pattern of meteorology be associated with the harbor seiches observed in some of the tide records? This report presents what results were obtained: in all cases they are preliminary rather than final.

Contents: Gravitationally Perturbed Elastic Waves; Deep Ocean Seismic Background Studies; The Gyroscopic Seismometer; and U.S. Navy Operation, CHASE V.

Ground motion as elastic deformation due to loading by ocean tides, low frequency ocean waves and atmospheric pressure variations has been examined both theoretically and observationally. The observations have been made using vertical accelerometers at frequencies from a cycle a day to 140 cycles per hour. (Author)

The Cagniard-deHoop method in generalized ray theory is extended to spherically layered media. The theory is approximate and is asymptotic in reciprocal fractional powers of the frequency. For mantle body wave phases it is estimated that the theory can be used for P pulses with periods less than 40 superscript s and S pulses with periods less than 75 superscript s. An initial application of the theory to the study of LRSM recordings of NTS events shows: (1) models derived from travel time data alone may have synthetic seismograms that disagree with observations; (2) the structure of the upper mantle beneath North America has very significant lateral variations in the uppermost 700 km. Some classical results in normal mode theory have recently been uncovered. They permit one to study the residual static displacement field, caused by an earthquake or explosion, in terms of the normal mode eigenfunctions. The dynamical and statistical fields have the same expansion coefficients in the normal mode representation. Consequently, there is an indirect method for finding static fields. (Author)

Contents: Constructing P-velocity models to fit restricted sets of travel-time data; Inversion of inaccurate gross earth data; Tidal to seismic frequency investigations with a quartz; Accelerometer of new geometry; Earth normal modes from a 6.5 magnitude earthquake; Microseism measurements on the deep ocean bottom; Ocean microseism measurements with a neutral bouyancy free- floating midwater seismometer; Seismic noise between 2.5 and 200 cycles per hour; and Linearization and calibration of electrostatically fedback gravity meters., Sponsored in part by the DARPA.

This version of the User's Guided supersedes a preliminary version which was issued in August of 1962. The user of the preliminary version should note changes in the control statements CYCLE, OPTION, KEEP, INSERT, END, MERGE, NORM, SARIT, and CROSC. Of these, only those to CYCLE, OPTION and MERGE will prevent a previously satisfactory control list from running. The functions indicated by numbers in the second item of the SARIT control statement have been changed and control statements READF, READF2, ENDFIL, TRUNC2, FOURTR and HARM added. In the CYCLE and OPTION control statements, the word CHK has been substituted for IND. The guide has been extensively rewritten to improve its intelligibility. (Author)

Contents: Surface Wave Detection with a Broad Band Accelerometer; High-Q Overtone Modes of the Earth; Report on a New Broad Band Vertical Accelerometer; Teleseismic Detection with Wide Band Vertical and Horizontal Accelerometers.

The vertical accelerometers were used to make a six month (January to July 1971) data collection run which is being used to determine detection thresholds and azimuthal dependences. This run was made at a surface site at Camp Elliott, San Diego. The horizontal accelerometers were completed and placed in operation and data gathered simultaneously with the vertical accelerometers for several months at a surface site at Camp Elliott, San Diego. Both a vertical and horizontal were used in a mine test at 5300 and 6700 feet. The results showed that the major improvement came in the horizontal data which showed no diurnal effect as is seen in the surface data., Sponsored in part by the DARPA.

The report discusses an experiment designed to study collisionless shock waves in an inverse pinch discharge using argon. A magnetic disturbance was generated which propagated ahead of the driving field at twice the piston speed. Measurements of the magnetic and electric field structures, electron density and temperature, as well as ion velocities revealed that the disturbance was produced by a beam of plasma moving through the ionized ambient plasma rather than by a true shock wave. Calculations of ion trajectories using measured electric fields demonstrated that the beam originated at small radii and early times, and was not the result of a steady specular reflection from the piston field. It is concluded that the ions comprising this stream, which were collisionless relative to the ambient ions, did not couple to the background plasma even though a strong magnetic field was applied. (Author)

It is desired to determine the location of an emission from multiple observations at long range. Each observation (an angle) will have attached to it, an associated variance. The possibility of apriori information as to location of the emission will be included. A Cartesian coordinate system will be utilized to delineate the estimate of the location of the emission. If no apriori information is known regarding the location of the emission, then the observation set is scanned to find the most reliable and accurate fixes. These are used to obtain a first pseudo apriori location of the emission, and its associated apriori variance. With an initial estimate of the location of the emission, extended Kalman filtering techniques can be utilized. These incorporate the use of perturbations from a nominal estimate in terms of the observation equation. Most processes or events of interest occur randomly in time. Examples of this phenomena are tidal wave (Tsunamis), earthquakes, and underground nuclear tests. Such detectors have some general attributes in common. These include background noise rejection, spurious data (glitches) rejection, signal band enhancement, and squaring or rectifying and integrating over a finite time and comparing with preset thresholds for detection. In addition, these devices should require a minimum of power and size and cost. As an example of such a system, a Tsunami detector is developed in detail. (Author)