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1: A model of the seismoscope invented by the Chinese scientist Zhang Heng (78-139) in AD 132. The instrument was two metres in diameter, with metal balls balanced in each of the eight dragons' mouths. Strong seismic tremors caused a ball to be released from the mouth of a dragon into the mouth of the frog below, sounding an alarm. The position of the ball falling indicated the direction of the shock wave.
Source publication
The book focuses on basic principles and from there explain the recent advances within various geophysical exploration techniques, in an easy way with limited use of equations but with many examples and illustrations. The chapters include:
1. Looking into the Earth
2. Elements of Seismic Surveying
3. Marine Seismic Sources and Sounds in the Sea...
Citations
... In the petroleum industry, 4D seismic is used as a primary surveillance tool to optimize field development plans and improve energy efficiency in operation and production. It is the process of using two or more seismic surveys acquired in the same area to find changes that occur over time (Landrø and Amundsen, 2018). Subsurface changes due to petroleum production or fluid substitution cause different responses of amplitude and traveltime in the seismic data acquired at different times. ...
In a time-lapse (also called 4D) seismic analysis, the time-shift of a certain seismic reflection event is caused by the changes in the seismic velocity and the depth of the event. An interpretation of 4D time-shifts is normally simplified by neglecting displacement changes (strains) or assuming a linear relation between thickness and velocity strains. Here, we go beyond these assumptions and propose a least-squares optimization method to simultaneously estimate the thickness and velocity strains in vertical transverse isotropic (VTI) media from angle-dependent 4D seismic time strains. Through examples from synthetic and field data, we show that the 4D thickness strains, velocity strains, and anisotropic parameter changes can be estimated simultaneously without prior knowledge about the geomechanics of the survey area. Our time-strain inversion method can be applied to any other 4D seismic data set in which angle-stack images are available. We see that our method has high potential in many other applications, because the thickness and velocity strains are the fundamental components of most physical properties used in 4D seismic and geomechanics applications.
... The ghost notch is exactly determined by the reciprocal of the arrival time difference between the direct and surface-reflected path, and that of approximately 120 Hz is predicted at the firing depth of 6 m at a close distance. When the distance between source and receiver increases, the arrival time difference decreases, and high-frequency ghost notches may occur at the long distances (Landrø and Amundsen, 2018). The median sound exposure spectral densities of full acoustic data with and without airgun sounds are represented by blue and red solid lines in Figure 4C, which were taken from the intensity average of the mean-square sound pressure spectral densities estimated from the 1minute segments compensated for the same time length of 4 sec as the airgun sound exposure spectral density. ...
A passive acoustic monitoring has been conducted by Korea Polar Research Institute (KOPRI) since 2017 in the East Siberian Sea using an autonomous passive acoustic recorder. Seismic airgun sounds, generated from the multichannel seismic survey system of the ice-breaking research vessel Araon, were measured from 18.6 km to 164.2 km in September 2019. During the survey, the R/V Araon maintained the ship’s trajectory at a constant heading and speed to obtain useful acoustic data for investigating the acoustic propagation properties with a distance between the source and receiver in shallow water. The decrease in sound pressure levels as a function of distance was compared with the least-square regression curves and numerical propagation modeling based on the parabolic equation. The broadband sounds in a low-frequency range were propagated over long distances with distinctive characteristics such as precursor arrivals, modal dispersion, and rapid decrease in spectrum level at low frequencies. Our results will be discussed in comparison with the sediment structure and geological history of the measurement region. [This research was supported by Korea Institute of Marine Science & Technology Promotion (KIMST) funded by the Ministry of Oceans and Fisheries (20210605, Korea-Arctic Ocean Warming and Response of Ecosystem, KOPRI and 20210632, Survey of Geology and Seabed Environmental Change in the Arctic Seas, KOPRI).]
... The seismic method is one of the most effective monitoring methods. However, several studies have demonstrated that time-lapse seismic data struggle to discriminate between fluid saturation and pore pressure changes [17,48]. On the other hand, the time-lapse CSEM method can be very useful in reservoir production monitoring, because of its high sensitivity to pore fluid saturation and the effects of pressure changes being negligible compared to seismic data [19]. ...
The marine controlled-source electromagnetic (CSEM) method has been used in different applications, such as oil and gas reservoir exploration, groundwater investigation, seawater intrusion studies and deep-sea mineral exploration. Recently, the utilization of the marine CSEM method has shifted from petroleum exploration to active monitoring due to increased environmental concerns related to hydrocarbon production. In this study, we utilize the various dynamic reservoir properties available through reservoir simulation of the Wisting field in the Norwegian part of the Barents Sea. In detail, we first developed geologically consistent rock physics models corresponding to reservoirs at different production phases, and then transformed them into resistivity models. The constructed resistivity models pertaining to different production phases can be used as input models for a finite difference time domain (FDTD) forward modeling workflow to simulate EM responses. This synthetic CSEM data can be studied and analyzed in the light of production-induced changes in the reservoir at different production phases. Our results demonstrate the ability of CSEM data to detect and capture production-induced changes in the fluid content of a producing hydrocarbon reservoir. The anomalous CSEM responses correlating to the reservoir resistivity change increase with the advance of the production phase, and a similar result is shown in anomalous transverse resistance (ATR) maps derived from the constructed resistivity models. Moreover, the responses at 30 Hz with a 3000 m offset resulted in the most pronounced anomalies at the Wisting reservoir. Hence, the method can effectively be used for production-monitoring purposes.
... The ghost notch is exactly determined by the reciprocal of the arrival time difference between the direct and surface-reflected path, and that of approximately 120 Hz is predicted at the firing depth of 6 m at a close distance. When the distance between source and receiver increases, the arrival time difference decreases, and high-frequency ghost notches may occur at the long distances (Landrø and Amundsen, 2018). The median sound exposure spectral densities of full acoustic data with and without airgun sounds are represented by blue and red solid lines in Figure 4C, which were taken from the intensity average of the mean-square sound pressure spectral densities estimated from the 1minute segments compensated for the same time length of 4 sec as the airgun sound exposure spectral density. ...
Seismic airgun sound was measured with an autonomous passive acoustic recorder as a function of distance from 18.6 to 164.2 km in shallow water (<70 m) at the continental shelf of the East Siberian Sea in September 2019. The least-square regression curves were derived in the zero-to-peak sound pressure level, sound exposure level, and band level in a frequency range between 10 and 300 Hz using the initial amplitude scaled from the near-field hydrophone data. In addition, propagation modeling based on the parabolic equation with the measured source spectrum was performed for range-dependent bathymetry, and the results were compared with the band level of the measurements. The sediment structure of the measurement area was a thin layer of iceberg-scoured postglacial mud overlying a fast bottom with high density based on grounding events of past ice masses. The observed precursor arrivals, modal dispersion, and rapid decrease in spectrum level at low frequencies can be explained by the condition of the high-velocity sediment. Our results can be applied to studies on the inversion of ocean boundary conditions and measurement geometry and basic data for noise impact assessment.
... It is well-known that the competing effect between the fundamental bubble of a marine air-gun source array and the source ghost response of the sea surface results in a strong attenuation of the lowest signal frequencies (below 7 Hz) (see e.g., Davies and Hampson, 2007;Parkes and Hegna, 2011;Landrø and Amundsen, 2018). However, many developments are seeking to fundamentally improve the ultralow-frequency source output. ...
An amplitude versus angle (AVA) inversion method is presented for estimating density and velocities of a stratified elastic medium from reflection seismograms in the intercept time-horizontal slowness domain. The elastic medium parameters are assumed to vary continuously with depth. The seismograms are Greens function pre-critical incidence primary P-wave reflections of time length T assumed to obey differential equations of a model for elastic primary P-wave back-scattering, similar to seismograms representing the first term in the well-known Bremmer series/WKBJ iterative solution model. A relation is found between plane-wave Greens function seismograms at each horizontal slowness and the medium properties in time. The Greens function seismograms after NMO-correction are directly inverted for the medium parameters as function of zero-offset traveltime. It is documented theoretically and verified numerically that the signal at the fundamental frequency f=1/ T must be present in the seismograms for the AVA method to provide the parameter trends of the elastic medium, implying that ultra-low frequencies <1 Hz for T >1 s must be generated and recorded. Noise in the seismograms at ultra-low frequencies is not considered since the theoretical AVA model does not handle microseisms that would be measured in real data. The main mathematical findings are illustrated by using simple model seismograms.
... of high-fold data and larger offset ranges than a standard towed-streamer marine survey (Landrø & Amundsen 2018). During processing, it is possible to filter the data by azimuth (i.e., the orientation of the receivers relative to the source) and by incidence angle (i.e., near, mid, far, and full stacks). ...
PS seismic data from the Snøhvit field are compared with seismic modelling to understand the effect of azimuthal separation and incidence angle on the imaging of faults and associated horizon discontinuities. In addition, the frequency content of seismic waves backscattered from faults is analysed. The study area consists of a horst structure delimited by a northern fault dipping NW and oblique to the E-W survey orientation, and a southern fault dipping SSW and subparallel to the survey. Due to the raypath asymmetry of PS reflections, the northern fault is imaged better by azimuthally partitioned W data that include receivers downdip of the fault, relative to the sources, than by E data where the receivers are updip from the sources. Partial stack data show a systematic increase in the PS fault-reflected amplitude and therefore quality of fault imaging with increasing incidence angle. Fault images are dominated by internal low-medium frequency shadows surrounded by medium-high frequencies haloes. Synthetic experiments suggest that this is due to the interaction of specular waves and diffractions, and the spectral contribution from the fault signal, which increases with fault zone complexity. These results highlight the impact of survey geometry and processing workflows on fault imaging.
Supplementary material: https://doi.org/10.6084/m9.figshare.c.5727552
... Seismic surveys are another prominent sound source. Seismic surveys are explorations of the geological structure beneath the seafloor using airguns (Gisiner, 2016;Landrø and Amundsen, 2018). A third prominent source is pile driving for offshore constructions such as wind turbines ). ...
... Marine seismic surveys are performed to explore the geological structure beneath the seafloor, often to search for oil and gas resources (Gisiner, 2016). They are conducted using a vessel towing one or two arrays of airguns and one up to more than ten streamers of hydrophones (Landrø and Amundsen, 2018). The airguns (seismic sources) produce high intensity, low-frequency impulsive sounds at regular intervals (5 -15 s), potentially for several hours and repeated for several days to weeks and even months . ...
Anthropogenic noise has been shown to affect marine animals in various ways, this may have fitness consequences at individual and population level. This thesis aims to increase insight into the quantification of sound-induced behavioural responses that are relevant to fitness, and into factors that modulate the responses. I addressed both knowledge gaps using captive and field studies on marine animals from multiple trophic levels. For the quantification of behavioural responses relevant to fitness, I examined the changes in time budgets of Atlantic cod in a net pen and basin in response to sound (chapter 2 and 3). To increase insight into factors that modulate sound impact, I examined the effect of various acoustic characteristics of sound stimuli and the environment on European seabass (chapter 4), the interaction between foraging shore crabs and common shrimps during noise (chapter 6), the cross-sensory interference by noise in foraging crabs (chapter 7), and habituation to repeated sound exposures by blue mussels (chapter 8). Future studies are needed to be able to link changes in time budgets to changes in energy budgets, and consequently to fitness. Additionally, studies into the factors that modulate the effects of sound are needed to fully understand the impact of sound.
... Methods for full waveform inversion (FWI) for high resolution velocity model building and amplitude-versusangle (AVA) inversion to recover elastic parameters all ask for low frequencies. Many developments are seeking to fundamentally improve ultra-low frequency source output (see, e.g, Hopperstad et al., 2012;Dellinger et al., 2016;Ronen and Chelminski, 2017;Amundsen et al., 2017;Landrø and Amundsen, 2018;Brittan et al., 2020;Chelminski et al., 2020;Robertsson, 2020). It is expected that the improvements we are seeing in source technology and associated improvements in sensor technology will soon be followed by improvements in data pre-processing with objective to separate signal from noise at ultra-low frequencies, below 1 Hz. ...
... Seabed seismic acquisition has been growing in the marine seismic market for its advantages over towed streamer techniques. The physics of seabed seismic acquisition is better than towed streamer acquisition for the following reasons (Landrø and Amundsen, 2018). ...
Distributed acoustic sensing (DAS) transforms submarine telecommunication cables into densely sampled seismic receivers. To demonstrate DAS applications for seismic imaging, we use an optical cable on the seafloor in the Trondheim Fjord, Norway, to record seismic data generated by a controlled seismic source. The data are simultaneously recorded by a towed hydrophone array and the fiber optic cable. Following our data processing methods, we can produce seismic images of the seafloor and underlying geological structures from both the hydrophone array data and the DAS data. We find that the DAS data and the hydrophone data have a comparable signal-to-noise ratio. Moreover, DAS images can be improved by using a seismic source that has sufficiently large energy within the frequency range matching the spatial resolution of DAS. The temporal resolution of the DAS images can be improved by minimizing the crossline offset between seismic sources and the DAS cable. The seismic images from DAS can be obtained to support geohazard analysis and various subsurface exploration activities.
... The existing methods are based on applying resistance directly from CSEM inversion results and inserting these into an appropriate saturation-resistivity relation, such as Archie's equation 7 or similar. Using porosity derived from Wyllie's equation 8 applied on the seismic-derived velocity, total resistivity from the CSEM, and assuming the water resistivity are known, the fluid saturation (S fl ) estimate can be obtained 9,10 . ...
... The EM method's structural resolution is poor, and without further constraint, the depth of objects of interest may be uncertain. As the EM wavelengths are much longer than seismic wavelengths, therefore, the vertical EM resolution is significantly lower than the vertical seismic resolution 9 . ...
Geological CO2 storage can be employed to reduce greenhouse gas emissions to the atmosphere. Depleted oil and gas reservoirs, deep saline aquifers, and coal beds are considered to be viable subsurface CO2 storage options. Remote monitoring is essential for observing CO2 plume migration and potential leak detection during and after injection. Leak detection is probably the main risk, though overall monitoring for the plume boundaries and verification of stored volumes are also necessary. There are many effective remote CO2 monitoring techniques with various benefits and limitations. We suggest a new approach using a combination of repeated seismic and electromagnetic surveys to delineate CO2 plume and estimate the gas saturation in a saline reservoir during the lifetime of a storage site. This study deals with the CO2 plume delineation and saturation estimation using a combination of seismic and electromagnetic or controlled-source electromagnetic (EM/CSEM) synthetic data. We assumed two scenarios over a period of 40 years; Case 1 was modeled assuming both seismic and EM repeated surveys were acquired, whereas, in Case 2, repeated EM surveys were taken with only before injection (baseline) 3D seismic data available. Our results show that monitoring the CO2 plume in terms of extent and saturation is possible both by (i) using a repeated seismic and electromagnetic, and (ii) using a baseline seismic in combination with repeated electromagnetic data. Due to the nature of the seismic and EM techniques, spatial coverage from the reservoir's base to the surface makes it possible to detect the CO2 plume’s lateral and vertical migration. However, the CSEM low resolution and depth uncertainties are some limitations that need consideration. These results also have implications for monitoring oil production—especially with water flooding, hydrocarbon exploration, and freshwater aquifer identification.
