Field trials of a seismoelectric method for detecting massive sulfides

Geophysics ◽  
1995 ◽  
Vol 60 (2) ◽  
pp. 365-373 ◽  
Author(s):  
Anton W. Kepic ◽  
Michael Maxwell ◽  
R. Don Russell
Keyword(s):  
Electromagnetic Radiation ◽  
Acoustic Waves ◽  
Seismic Energy ◽  
Field Trials ◽  
P Wave ◽  
Massive Sulfides ◽  
P Wave Velocity ◽  
Electromagnetic Emissions ◽  
First Arrival ◽  
Exploration Tool

An underground test of a seismoelectric prospecting method for massive sulfides was performed at the Mobrun Mine (Rouyn‐Noranda, Quebec) in June 1991. The method is based upon the conversion of seismic energy to high‐frequency pulses of electromagnetic radiation by sulfide minerals. The delay between shot detonation and detection of the electromagnetic radiation gives a one‐way traveltime for the acoustic wave to reach the zone of seismoelectric conversion, which when combined with P‐wave velocity allows the shot‐to‐ore zone distance to be calculated. A 0.22-kg explosive charge located within 50 m of the orebody provided the seismic excitation, and the resulting electromagnetic emissions were received by electric dipole and induction‐coil antennas. First‐arrival information from a 35‐shot survey above an orebody, the 1100 lens, provides firm evidence that short duration pulses of electromagnetic radiation are produced by the passage of acoustic waves through the orebody. The survey also demonstrated that seismoelectric conversions could be induced at shot‐to‐orebody distances of 50 m and detected at distances of up to 150 m from the orebody. Areas of seismoelectric conversion are highlighted in sections produced by plotting the position of seismic wavefronts during signal reception. The sections show anomalies that correlate with the known structure and location of the orebody and demonstrate the potential of using this seismoelectric phenomenon as an exploration tool.

The structural architecture of the Whataroa Valley at the Alpine Fault (New Zealand) from first-arrival tomography and reflection imaging using an extended 3D VSP survey

2020 ◽  
Author(s):  
Vera Lay ◽  
Stefan Buske ◽  
Sascha Barbara Bodenburg ◽  
Franz Kleine ◽  
John Townend ◽  
...  
Keyword(s):  
New Zealand ◽  
Seismic Data ◽  
Average Velocity ◽  
Velocity Model ◽  
P Wave ◽  
3D Seismic ◽  
Data Set ◽  
Alpine Fault ◽  
P Wave Velocity ◽  
First Arrival

<p>The Alpine Fault along the West Coast of the South Island (New Zealand) is a major plate boundary that is expected to rupture in the next 50 years, likely as a magnitude 8 earthquake. The Deep Fault Drilling Project (DFDP) aims to deliver insight into the geological structure of this fault zone and its evolution by drilling and sampling the Alpine Fault at depth.  </p><p>Here we present results from a 3D seismic survey around the DFDP-2 drill site in the Whataroa Valley where the drillhole penetrated almost down to the fault surface. Within the glacial valley, we collected 3D seismic data to constrain valley structures that were obscured in previous 2D seismic data. The new data consist of a 3D extended vertical seismic profiling (VSP) survey using three-component receivers and a fibre optic cable in the DFDP-2B borehole as well as a variety of receivers at the surface.</p><p>The data set enables us to derive a reliable 3D P-wave velocity model by first-arrival travel time tomography. We identify a 100-460 m thick sediment layer (average velocity 2200±400 m/s) above the basement (average velocity 4200±500 m/s). Particularly on the western valley side, a region of high velocities steeply rises to the surface and mimics the topography. We interpret this to be the infilled flank of the glacial valley that has been eroded into the basement. In general, the 3D structures implied by the velocity model on the upthrown (Pacific Plate) side of the Alpine Fault correlate well with the surface topography and borehole findings.</p><p>A reliable velocity model is not only valuable by itself but it is also required as input for prestack depth migration (PSDM). We performed PSDM with a part of the 3D data set to derive a structural image of the subsurface within the Whataroa Valley. The top of the basement identified in the P-wave velocity model coincides well with reflectors in the migrated images so that we can analyse the geometry of the basement in detail.</p>

Crosshole seismic imaging for sulfide orebody delineation near Sudbury, Ontario, Canada

Geophysics ◽  
2000 ◽  
Vol 65 (6) ◽  
pp. 1900-1907 ◽  
Author(s):  
Joe Wong
Keyword(s):  
Cost Effective ◽  
Massive Sulfide ◽  
P Wave ◽  
Mining Operations ◽  
Seismic Surveys ◽  
Ore Bodies ◽  
P Wave Velocity ◽  
Sulfide Ore ◽  
First Arrival ◽  
Discrete Layer

Crosshole seismic instrumentation based on a piezoelectric source and hydrophone detectors were used to gather seismograms between boreholes at the McConnell orebody near Sudbury, Ontario. High‐frequency seismograms were recorded across rock sections 50 to 100 m wide containing a continuous zone of massive sulfide ore. First‐arrival traveltimes obtained from a detailed scan were used to create a P-wave velocity tomogram that clearly delineated the ore zone. Refraction ray tracing on a discrete layer model confirmed the main features of the tomogram. The survey demonstrated that it is possible to conduct cost‐effective, high‐resolution crosshole seismic surveys to delineate ore bodies on a scale useful for planning mining operations.

scholarly journals ESTIMASI SEBARAN HIDROKARBON DENGAN MENGGUNAKAN INDIKATOR P-WAVE DIFFERENCE DISPERSION FACTOR PADA LAPANGAN BONAPARTE

2020 ◽  
Vol 5 (3) ◽  
pp. 45-54
Author(s):  
Mokhammad Puput Erlangga ◽  
Handoyo Handoyo ◽  
Egie Wijaksono
Keyword(s):  
Wave Velocity ◽  
Seismic Wave ◽  
Physical Property ◽  
Seismic Energy ◽  
Wave Dispersion ◽  
Hydrocarbon Exploration ◽  
P Wave ◽  
P Wave Velocity ◽  
Saturated Media ◽  
Standing Problem

In the hydrocarbon  exploration, we need the method that result the direct hydrocarbon indicator to estimate the reservoir location and dimension accurately. It is a difficult and long standing problem. The method that used before was inverting the linearized of Zoepprit’s equation. But this method would not result the physical property depend on frequency. We know that the seismic wave propagate in the porous and fluid saturated media will attenuate and wave dispersion. This phenomenon is caused by the dissipation of seismic energy that depend on frequency. So by this idea, we will use the frequency-dependent of physical property to improve the accuracy of direct hydrocarbon indicator. The physical property will be used here is the P-Wave velocity. The method is call the P-Wave Difference Dispersion Factor (PPDF).

Characterizing an unstable mountain slope using shallow 2D and 3D seismic tomography

Geophysics ◽  
2006 ◽  
Vol 71 (6) ◽  
pp. B241-B256 ◽  
Author(s):  
Bjoern Heincke ◽  
Hansruedi Maurer ◽  
Alan G. Green ◽  
Heike Willenberg ◽  
Tom Spillmann ◽  
...  
Keyword(s):  
Rock Mass ◽  
Seismic Refraction ◽  
P Wave ◽  
Fracture Zones ◽  
Mountain Slope ◽  
Low Field ◽  
P Wave Velocity ◽  
First Arrival ◽  
Mobile Segment ◽  
2D And 3D

As transport routes and population centers in mountainous areas expand, risks associated with rockfalls and rockslides grow at an alarming rate. As a consequence, there is an urgent need to delineate mountain slopes susceptible to catastrophic collapse in a safe and noninvasive manner. For this purpose, we have developed a 3D tomographic seismic refraction technique and applied it to an unstable alpine mountain slope, a significant segment of which is moving at [Formula: see text] toward the adjacent valley floor. First arrivals recorded across an extensive region of the exposed gneissic rock mass have extraordinarily low apparent velocities at short [Formula: see text] to long [Formula: see text] shot-receiver offsets. Inversion of the first-arrival traveltimes produces a 3D tomogram that reveals the presence of a huge volume of very-low-quality rock with ultralow to very low P-wave velocities of [Formula: see text]. These values are astonishingly low compared to the average horizontal P-wave velocity of [Formula: see text] determined from laboratory analyses of intact rocks collected at the investigation site. The extremely low field velocities likely result from the ubiquitous presence of dry cracks, fracture zones, and faults on a wide variety of scales. They extend to more than [Formula: see text] depth over a [Formula: see text] area that encompasses the mobile segment of the mountain slope, which is transected by a number of actively opening fracture zones and faults, and a large part of the adjacent stationary slope. Although hazards related to the mobile segment have been recognized since the last major rockslides affected the mountain in 1991, those related to the adjacent low-quality stationary rock mass have not.

Distribution of subglacial sediment layers around a DAS-instrumented borehole, Store Glacier, Greenland

2021 ◽  
Author(s):  
Adam Booth ◽  
Poul Christoffersen ◽  
Joseph Chapman ◽  
Charlotte Schoonman ◽  
Bryn Hubbard ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Seismic Reflection ◽  
Seismic Energy ◽  
P Wave ◽  
Sediment Layer ◽  
Sediment Thickness ◽  
P Wave Velocity ◽  
Vsp Data ◽  
Sediment Layers ◽  
Strong Control

<p>Distributed acoustic sensing (DAS) involves detecting seismic energy from the deformation of a length of optical fibre cable, offers considerable potential in the high-resolution monitoring of glacier systems. Subglacial conditions and sediment properties exert a strong control on the basal sliding rate of glaciers, but identifying the connectivity of drainage pathways and their hydraulic conductivity remains poorly understood. This is due in part to the limitations of instrumental methods to monitor these processes accurately, whether by locating cryoseismic emissions in passive seismic records or actively imaging the subglacial environment in seismic reflection surveys.  Here, we explore the application of a borehole survey geometry for constraining the thickness and distribution of subglacial sediment deposits around a DAS installation on Greenland’s Store Glacier.</p><p>Store Glacier is a fast-moving outlet of the Greenland Ice Sheet. The instrumented borehole is drilled near the centre of a drained supraglacial meltwater lake, 28 km upstream of the Store Glacier terminus, and within 100 m of an active moulin, representing a continuous supply of water to the glacier bed. The borehole, which terminates at the glacier bed at a depth of 1043 m depth, is instrumented throughout its length with Solifos BruSENS fibre-optic cable, and monitored with a Silixa iDAS<sup>TM</sup> interrogator. A suite of ~30 vertical seismic profiles (VSPs) was recorded at various azimuths and offsets (up to 500 m) from the borehole, using a 7 kg sledgehammer source. </p><p>Initial analyses of VSP data implied a 20 [+17, -2] m thickness of sediment immediately beneath the borehole. These analyses are refined by considering the full suite of VSP data, to map spatial variations in the thickness of subglacial sediment layers.  This is undertaken using an iterative ray-tracing scheme, which seeks to minimise the differences in the arrival-time of direct seismic energy and subglacial reflections received at various depths in the borehole. Englacial compressional (P-) wave velocities are measured from cross-correlating direct arrivals (= 3700 ± 75 m/s in the upper 800 m of the glacier, 4000 ± 75 m/s between 880-950 m, 3730 ± 75 m/s through basal ice). For the subglacial sediment, we use a P-wave velocity of 1839 m/s, consistent with a value constrained in nearby surface seismic reflection data. To improve the definition of subglacial reflections and the constraint of their arrival times, data are first enhanced using frequency-wavenumber filtering.</p><p>Our approach suggests that sediment thickness is ~30 m directly beneath the borehole, potentially thinning by 10 m approximately 75 m further south. In reality, the seismic velocity through the sediment layer is unconstrained, but travel-time variations are themselves indicative of changes in either P-wave velocity and/or sediment thickness. Our work further highlights the interpretative potential of borehole DAS approaches, in support of conventional surface-based seismic analysis.</p>

Empirical Equations of P-Wave Velocity in the Shallow and Semi-Deep Sea Sediments from the South China Sea

2021 ◽  
Vol 20 (3) ◽  
pp. 532-538
Author(s):  
Guanbao Li ◽  
Zhengyu Hou ◽  
Jingqiang Wang ◽  
Guangming Kan ◽  
Baohua Liu
Keyword(s):  
South China Sea ◽  
Wave Velocity ◽  
South China ◽  
Deep Sea ◽  
The South China Sea ◽  
P Wave ◽  
Empirical Equations ◽  
China Sea ◽  
P Wave Velocity ◽  
Deep Sea Sediments
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