GEOPHYSICAL EXPLORATION FOR LIMESTONE REEFS

Geophysics ◽  
1949 ◽  
Vol 14 (4) ◽  
pp. 486-500
Author(s):  
F. J. Agnich
Keyword(s):  
Seismic Data ◽  
Geophysical Methods ◽  
Geophysical Exploration ◽  
Isopach Maps ◽  
Velocity Variations

Various geophysical methods are discussed in relation to their possible value in locating limestone reefs, with special emphasis on the gravity meter and seismograph. The effects of possible velocity variations through reefs on reflections from below a reef body are examined. Relationships between the shallow and deep horizons indicate that time isopach maps of such seismic data extremely valuable. A suggested exploration procedure describes several detailing methods, and emphasizes the important role of the interpreter in solving the problems associated with exploration for limestone reefs.

The Role of Seismic Data in the Exploration and Development of Carbonate Karst Cave Reservoir

2014 ◽  
Author(s):  
Zhenzhong Cai ◽  
Chunduan Zhao ◽  
Xingliang Deng ◽  
Yanming Tong ◽  
Yangyong Pan ◽  
...  
Keyword(s):  
Seismic Data ◽  
Karst Cave ◽  
Exploration And Development

scholarly journals Integrated magnetotelluric and seismic investigation of Cenozoic graben structure near Obrzycko, Poland

2021 ◽  
Author(s):  
Adam Cygal ◽  
Michał Stefaniuk ◽  
Anna Kret
Keyword(s):  
Seismic Data ◽  
Geophysical Methods ◽  
Geological Structure ◽  
Data Sets ◽  
Low Velocity ◽  
Shallow Subsurface ◽  
Geophysical Model ◽  
Novel Approach ◽  
Loose Deposits ◽  
Static Corrections

AbstractThis article presents the results of an integrated interpretation of measurements made using Audio-Magnetotellurics and Seismic Reflection geophysical methods. The obtained results were used to build an integrated geophysical model of shallow subsurface cover consisting of Cenozoic deposits, which then formed the basis for a detailed lithological and tectonic interpretation of deeper Mesozoic sediments. Such shallow covers, consisting mainly of glacial Pleistocene deposits, are typical for central and northern Poland. This investigation concentrated on delineating the accurate geometry of Obrzycko Cenozoic graben structure filled with loose deposits, as it was of great importance to the acquisition, processing and interpretation of seismic data that was to reveal the tectonic structure of the Cretaceous and Jurassic sediments which underly the study area. Previously, some problems with estimation of seismic static corrections over similar grabens filled with more recent, low-velocity deposits were encountered. Therefore, a novel approach to estimating the exact thickness of such shallow cover consisting of low-velocity deposits was applied in the presented investigation. The study shows that some alternative geophysical data sets (such as magnetotellurics) can be used to significantly improve the imaging of geological structure in areas where seismic data are very distorted or too noisy to be used alone

Time-Lapse Monitoring of Daily Velocity Changes in Binchuan, Southwestern China, Using Large-Volume Air-Gun Source Array Data

2022 ◽  
Author(s):  
Yi Luan ◽  
Hongfeng Yang ◽  
Baoshan Wang ◽  
Wei Yang ◽  
Weitao Wang ◽  
...  
Keyword(s):  
Large Volume ◽  
Seismic Data ◽  
Temporal Changes ◽  
Air Pressure ◽  
Southwestern China ◽  
Long Period ◽  
Air Gun ◽  
Velocity Variations ◽  
Velocity Changes ◽  
Source Array

Abstract Temporal changes of seismic velocities in the Earth’s crust can be induced by stress perturbations or material damage from reasons such as strong ground motion, volcanic activities, and atmospheric effects. However, monitoring the temporal changes remains challenging, because most of them generally exist in small travel-time differences of seismic data. Here, we present an excellent case of daily variations of the subsurface structure detected using a large-volume air-gun source array of one-month experiment in Binchuan, Yunnan, southwestern China. The seismic data were recorded by 12 stations within ∼10 km away from the source and used to detect velocity change in the crust using the deconvolution method and sliding window cross-correlation method, which can eliminate the “intercept” error when cutting the air-gun signals and get the real subsurface variations. Furthermore, the multichannel singular spectral analysis method is used to separate the daily change (∼1 cycle per day) from the “long-period” change (<1 cycle per day) or noise. The result suggests that the daily velocity changes at the two nearest stations, 53277 (offset ∼700 m) and 53278 (offset ∼2.3 km), are well correlated with air temperature variation with a time lag of 5.0 ± 1.5 hr, which reflects that the velocity variations at the subsurface are likely attributed to thermoelastic strain. In contrast, both daily and long-period velocity changes at distant stations correlate better with the varying air pressure than the temperature, indicating that the velocity variations at deeper depth are dominated by the elastic loading of air pressure. Our results demonstrate that the air-gun source is a powerful tool to detect the velocity variation of the shallow crust media.

scholarly journals Role of Upper-Flow-Regime Bedforms Emplaced by Sediment Gravity Flows in the Evolution of Deltas

2019 ◽  
Vol 7 (1) ◽  
pp. 5 ◽  
Author(s):  
Svetlana Kostic ◽  
Daniele Casalbore ◽  
Francesco Chiocci ◽  
Jörg Lang ◽  
Jutta Winsemann
Keyword(s):  
Numerical Analysis ◽  
High Resolution ◽  
Flow Regime ◽  
Case Studies ◽  
Seismic Data ◽  
Lake Level ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Digital Elevation

Upper-flow-regime bedforms and their role in the evolution of marine and lacustrine deltas are not well understood. Wave-like undulations on delta foresets are by far the most commonly reported bedforms on deltas and it will take time before many of these features get identified as upper-flow-regime bedforms. This study aims at: (1) Providing a summary of our knowledge to date on deltaic bedforms emplaced by sediment gravity flows; (2) illustrating that these features are most likely transitional upper-flow-regime bedforms; and (3) using field case studies of two markedly different deltas in order to examine their role in the evolution of deltas. The study combines numerical analysis with digital elevation models, outcrop, borehole, and high-resolution seismic data. The Mazzarrà river delta in the Gulf of Patti, Italy, is selected to show that upper-flow-regime bedforms in gullies can be linked to the onset, growth, and evolution of marine deltas via processes of gully initiation, filling, and maintenance. Ice-marginal lacustrine deltas in Germany are selected as they illustrate the importance of unconfined upper-flow-regime bedforms in the onset and evolution of distinct delta morphologies under different lake-level trends.

Role of the creeping segment in the synchronization of earthquake cycles on oceanic transform faults revealed by numerical simulations in the framework of rate-and-state friction

2020 ◽  
Author(s):  
Meng Wei ◽  
Pengcheng Shi
Keyword(s):  
Seismic Data ◽  
Numerical Models ◽  
General Idea ◽  
Partial Rupture ◽  
Transform Faults ◽  
Seismic Slip ◽  
Rate And State Friction ◽  
Large Earthquakes ◽  
Earthquake Cycles

<p>Synchronization behavior of large earthquakes, rupture of nearby faults close in time for many cycles, has been reported in many fault systems. The general idea is that the faults in the system have similar repeating interval and are positively coupled through stress interaction. However, many details of such synchronization remain unknown. Here, we built numerical models in the framework of rate-and-state friction to simulate earthquake cycles on the west Gofar fault, an oceanic transform fault in the East Pacific Rise. Our model is consisted of two seismic segments, separated by a creeping segment, for which the size and location is constrained by seismic data. The parameters in the seismic segments were set to reproduce M6 earthquakes every 5 years, to be consistent with observation. We varied the parameters in the creeping segment to understand its role on earthquake synchronization. We found that the width and the strength of the creeping segment will determine the synchronization of earthquake cycles on the two seismic segments. When the creeping segment is relatively narrow or weak, the system will become synchronized quickly and the synchronization remains for many cycles. When it is relatively wide or strong, the earthquake cycles on the two segments are not related but could be synchronized by chance. In both cases, earthquakes tend to rupture the entire seismic segment. Between these two end-member situations, the system fluctuated between synchronization and non-synchronization on the time scale of 5-10 cycles. The switch always happens when the partial rupture of the seismic segment occurs, resulting in moderate size earthquakes (M4-5) and earthquake cycle shift, which is likely caused by stress interaction through the creeping segment. Here, we conclude that the co-seismic slip and aseismic after slip in the creeping segment could promote the synchronization of earthquake cycles on oceanic transform faults, and likely in other tectonic systems. In addition, the average seismic ratio of the entire fault can be quite low, ranging between 0.2-0.4 because of the barrier segment. We suggest that the existence of creep segments contributed significantly to the well-observed low seismic ratio on oceanic transform faults.</p>

GEOPHYSICAL ACTIVITY IN 1962

Geophysics ◽  
1963 ◽  
Vol 28 (6) ◽  
pp. 1049-1071
Author(s):  
Neal J. Smith
Keyword(s):  
Geophysical Methods ◽  
The Other ◽  
Free World ◽  
Geophysical Exploration ◽  
Other Hand ◽  
Ground Magnetic

Petroleum geophysical exploration in the Free World, consisting of seismic, gravity, ground magnetic, and other nonairborne geophysical methods, declined 10.0 percent over 1961. This is the sharpest in the continual series of declines that began in 1957 and amounts to a loss of 1,008 crew‐months; it is 32 percent down from the peak year of 1956. Airborne magnetometer activity, on the other hand, rose from 347,841 line‐miles in 1961 to 433,473, an increase of 25 percent.

EXPLORATION WORK IN MEXICO

Geophysics ◽  
1953 ◽  
Vol 18 (1) ◽  
pp. 188-200
Author(s):  
Antonio Garcia Rojas
Keyword(s):  
United States ◽  
Gulf Coast ◽  
Geophysical Methods ◽  
The United States ◽  
Oil Fields ◽  
Present Level ◽  
Geophysical Exploration ◽  
Petroleos Mexicanos ◽  
The Difference

Since 1940 Mexico has increased exploration work in search of new oil fields. Most of the exploration has been done in the Gulf Coast area where all existing Mexican oil fields are located. A brief résumé is given of the main problems of the different provinces under exploration and a list of the fields discovered by Petróleos Mexicanos in the different provinces of the country. Geophysical methods have been responsible for location of a very large percent of the new fields. To compare the intensity of exploration in the United States and Mexico, the amount of seismic and gravity‐meter work and of wildcat drilling per million barrels of production is given for both countries. The data shows that Mexico’s level of geophysical exploration, per million barrels of oil produced, is very close to that of the United States. A very marked increase in the intensity of exploration is shown for both countries. Wildcat drilling in Mexico has been less intensive than in the United States but shows a definite tendency to increase; its present level is very close to that of the United States during 1940. The writer is of the opinion that the difference in intensity of wildcat drilling shown in the data presented is actually smaller than appears as there is a certain amount of duplication in the United States because of leaseholding problems.

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