Visual and Passive Acoustic Marine Mammal Observations and High-Frequency Seismic Source Characteristics Recorded During a Seismic Survey

2007 ◽  
Vol 32 (2) ◽  
pp. 469-483 ◽  
Author(s):  
J.R. Potter ◽  
M. Thillet ◽  
C. Douglas ◽  
M.A. Chitre ◽  
Z. Doborzynski ◽  
...  
Keyword(s):  
Marine Mammal ◽  
High Frequency ◽  
Seismic Source ◽  
Seismic Survey ◽  
Source Characteristics ◽  
Passive Acoustic

Seismic source characteristics from explosion-generated P waves

1968 ◽  
Vol 58 (6) ◽  
pp. 1833-1848 ◽  
Author(s):  
Lynn D. Trembly ◽  
Joseph W. Berg
Keyword(s):  
High Frequency ◽  
Transfer Functions ◽  
Low Frequency ◽  
Seismic Energy ◽  
Seismic Source ◽  
Propagation Path ◽  
P Waves ◽  
Nuclear Explosions ◽  
Source Characteristics ◽  
The Earth

ABSTRACT Signals from nuclear explosions were used to calibrate seismograph stations (near-regional, regional, and teleseismic ranges) by determining the transfer functions of the lumped source-propagation path-receiver systems. Recorded signals other than those used for calibration purposes were used to derive the characteristics of the sources. It was found that source functions could be derived from distant signals when the frequencies of the output signals were reliably related to the source. For the output data used in this research, the low-frequency cutoff was 0.2 cps at all stations and the high-frequency cutoffs were 4.0, 3.0, and 2.0 cps at the near-regional, regional, and teleseismic distances, respectively. The low-frequency cutoff was due mainly to the recording instruments, and the high-frequency cutoffs were due to the attentuation of the seismic energy by the Earth. The most reliable results were obtained when three half-cycles of the observed output signals (first arrivals) were used. When explosions in granite were used as calibration sources, the energies derived for explosions in tuff, alluvium, and dolomite media were 88, 65, and 12 per cent of the respective “observed” source energies.

scholarly journals Acoustic Source Data for Medium Speed IC-Engines

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Antti Hynninen ◽  
Raimo Turunen ◽  
Mats Åbom ◽  
Hans Bodén
Keyword(s):  
High Frequency ◽  
Internal Combustion Engines ◽  
Low Frequency ◽  
Acoustic Source ◽  
Ic Engine ◽  
Source Characteristics ◽  
Medium Speed ◽  
Source Data ◽  
Exhaust Noise ◽  
Ic Engines

Knowledge of the acoustic source characteristics of internal combustion engines (IC-engines) is of great importance when designing the exhaust duct system and its components to withstand the resulting dynamic loads and to reduce the exhaust noise emission. The goal of the present study is to numerically and experimentally investigate the medium speed IC-engine acoustic source characteristics, not only in the plane wave range but also in the high frequency range. The low frequency acoustic source characteristics were predicted by simulating the acoustic multiload measurements by using a one-dimensional process simulation code. The low frequency in-duct exhaust noise of a medium speed IC-engine can be quite accurately predicted. The high frequency source data is estimated by averaging the measured acoustic pressures with different methods; using the simple cross-spectra averaging method seems promising in this instance.

Far-offset detection of normal modes and diving waves: a case study in Valhall, southern North Sea

Geophysics ◽  
2021 ◽  
pp. 1-50
Author(s):  
Filipe Borges ◽  
Martin Landrø
Keyword(s):  
Normal Modes ◽  
Seismic Source ◽  
Velocity Model ◽  
Seismic Survey ◽  
The Past ◽  
Lack Of Control ◽  
Record Data ◽  
Refracted Waves ◽  
1D Velocity Model

The use of permanent arrays for continuous reservoir monitoring has become a reality in the past decades, with Ekofisk and Valhall being its flagships. One of the possibilities when such solution is available is to passively record data while acquisitions with an active source are ongoing in nearby areas. These recordings might contain ultrafar-offset data (over 30 km), which are hardly used in standard reservoir exploration and monitoring, as they are mostly a combination of normal modes, deep reflections and diving waves. We present here data from the Valhall Life of Field Seismic array, recorded while an active seismic survey was being acquired in Ekofisk, in April 2014. Despite the lack of control on source firing time and position, analysis of the data shows that the normal modes are remarkably clear, overcoming the ambient noise in the field. The normal modes can be well explained by a two-layer acoustic model, while a combination of diving waves and refracted waves can be fairly well reproduced with a regional 1D velocity model. We suggest a method to use the far-offset recordings to monitor changes in the shallow sediments between source and receivers, both with and without a coherent seismic source in the area.

Glider-Based Passive Acoustic Monitoring in the Arctic

2014 ◽  
Vol 48 (5) ◽  
pp. 40-51 ◽  
Author(s):  
Mark F. Baumgartner ◽  
Kathleen M. Stafford ◽  
Peter Winsor ◽  
Hank Statscewich ◽  
David M. Fratantoni
Keyword(s):  
Real Time ◽  
Marine Mammal ◽  
Low Frequency ◽  
Acoustic Monitoring ◽  
Bowhead Whale ◽  
The Arctic ◽  
Mammal Species ◽  
Frequency Detection ◽  
Passive Acoustic ◽  
The Impact

AbstractPersistently poor weather in the Arctic makes traditional marine mammal research from aircraft and ships difficult, yet collecting information on marine mammal distribution and habitat utilization is vital for understanding the impact of climate change on Arctic ecosystems. Moreover, as industrial use of the Arctic increases with the expansion of the open-water summer season, there is an urgent need to monitor the effects of noise from oil and gas exploration and commercial shipping on marine mammals. During September 2013, we deployed a single Slocum glider equipped with a digital acoustic monitoring (DMON) instrument to record and process in situ low-frequency (<5 kHz) audio to characterize marine mammal occurrence and habitat as well as ambient noise in the Chukchi Sea off the northwest coast of Alaska, USA. The DMON was programmed with the low-frequency detection and classification system (LFDCS) to autonomously detect and classify sounds of a variety of Arctic and sub-Arctic marine mammal species. The DMON/LFDCS reported regularly in near real time via Iridium satellite detailed detection data, summary classification information, and spectra of background noise. The spatial distributions of bowhead whale, bearded seal, and walrus call rates were correlated with surface salinity measured by the glider. Bowhead whale and walrus call rates were strongly associated with a warm and salty water mass of Bering Sea origin. With a passive acoustic capability that allows both archival recording and near real-time reporting, we envision ocean gliders will become a standard tool for marine mammal and ocean noise research and monitoring in the Arctic.

scholarly journals Seismic reflection imaging of a geothermal aquifer in an urban setting

Geophysics ◽  
1998 ◽  
Vol 63 (4) ◽  
pp. 1285-1294 ◽  
Author(s):  
Lee Liberty
Keyword(s):  
Seismic Reflection ◽  
Seismic Source ◽  
Urban Setting ◽  
Seismic Survey ◽  
Quality Data ◽  
Signal Quality ◽  
Fracture Permeability ◽  
Air Gun ◽  
Explosive Source ◽  
Geothermal Aquifer

A seismic reflection survey that was conducted in downtown Boise, Idaho, to help city planners site a new well for injection of spent geothermal water illustrates some methods to safely and successfully employ a seismic reflection survey in an urban setting. The objective of the seismic survey was to estimate the depth and continuity of a basalt and rhyolite volcanic sequence. Well siting was based on geothermal aquifer depth, location of interpreted faults, projected thermal impact of injection on existing wells, surface pipe extension costs, and public land availability. Seismic acquisition tests and careful processing were used to ensure high‐quality data while minimizing the potential for damage along city streets. A video camera placed in a sewer and a blast vibration monitor were used to confirm that energy from the seismic source (a 75-in3 land air gun) did not damage nearby buildings, street surfaces, or buried utilities along the survey lines. Walkaway seismic tests were also used to compare signal quality of the air‐gun source to an explosive source for imaging targets up to 800 m depth. These tests show less signal bandwidth from the air‐gun source compared to the buried explosive source, but the air‐gun signal quality was adequate to meet imaging objectives. Seismic reflection results show that the top of this rhyolite/basalt sequence dips (∼8–11°) southwest away from the Boise foothills at depths of 200 to 800 m. Seismic methods enabled interpretation of aquifer depths along the profiles and located fault zones where injected water may encounter fracture permeability and optimally benefit the existing producing system. The acquisition and processing techniques used to locate the Boise injection well may succeed for other hydrogeologic and environmental studies in urban settings.

Shallow to very shallow, high‐resolution reflection seismic using a portable vibrator system

Geophysics ◽  
1998 ◽  
Vol 63 (4) ◽  
pp. 1295-1309 ◽  
Author(s):  
Ranajit Ghose ◽  
Vincent Nijhof ◽  
Jan Brouwer ◽  
Yoshikazu Matsubara ◽  
Yasuhiro Kaida ◽  
...  
Keyword(s):  
High Resolution ◽  
High Frequency ◽  
Seismic Waves ◽  
Soft Soil ◽  
Geophysical Methods ◽  
Seismic Source ◽  
P Wave ◽  
Nondestructive Technique ◽  
Buried Objects ◽  
Reflection Seismic

In shallow engineering‐geophysical applications, there is a lack of controlled, nondestructive, high‐resolution mapping tools, particularly for the target depth that ground‐penetrating radar cannot reach but which is too shallow for other conventional geophysical methods. For soft soil, this corresponds to a depth of 2 to 30 m. We have developed a portable, high‐frequency P-wave vibrator system that is capable of bridging this gap. As far as the important contribution of the seismic source is concerned, penetration and resolution can be individually controlled through easy modulation of the sweep signal generated by this electromagnetic vibrator. The feasibility of this system has been tested in shallow (10–50 m) to very shallow (0–10 m) applications. Seven field data sets representing varying geology, site conditions, and exploration targets are presented to illustrate the applicability. The first three examples show the potential of this portable vibrator source in shallow applications. Under favorable situations, a maximum resolution of about 20 cm for events located at 15–30 m depth could be achieved. Because high‐frequency seismic waves suffer from severe attenuation in the dry, unsaturated weathered zone, the penetration is relatively limited when the water table is deeper than 4–5 m. The fourth to seventh field examples illustrate very shallow applications at noisy, asphalt‐paved urban sites that are often encountered in civil, geotechnical, and environmental engineering projects. The prospecting targets were thin soil layers or small buried objects. On asphalt, the vibrator can produce high‐frequency energy easily. The fourth example shows high‐resolution delineation of very shallow soil structures. The last three examples present successful location of buried bodies—often small and closely spaced—in soft soil at depths of 0.5 to 5 m. We observe well‐defined reflection events of frequency exceeding 200 Hz. These results suggest that high‐frequency seismic reflection imaging using the portable vibrator system can indeed serve as a powerful, nondestructive technique for shallow to very shallow underground prospecting.

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