Recording seismic reflections using rigidly interconnected geophones

This is the publisher's version, also available electronically from "http://library.seg.org".Ultrashallow seismic reflection surveys require dense spatial sampling during data acquisition, which increases their cost. In previous efforts to find ways to reduce these costs, we connected geophones rigidly to pieces of channel iron attached to a farm implement. This method allowed us to plant the geophones in the ground quickly and automatically. The rigidly interconnected geophones used in these earlier studies detected first‐arrival energy along with minor interfering seismic modes, but they did not detect seismic reflections. To examine further the feasibility of developing rigid geophone emplacement systems to detect seismic reflections, we experimented with four pieces of channel iron, each 2.7 m long and 10 cm wide. Each segment was equipped with 18 geophones rigidly attached to the channel iron at 15‐cm intervals, and the spikes attached to all 18 geophones were pushed into the ground simultaneously. The geophones detected both refracted and reflected energy; however, no significant signal distortion or interference attributable to the rigid coupling of the geophones to the channel iron was observed in the data. The interfering seismic modes mentioned from the previous experiments were not detected, nor was any P‐wave propagation noted within the channel iron. These results show promise for automating and reducing the cost of ultrashallow seismic reflection and refraction surveys

Toward the autojuggie: Planting 72 geophones in 2 seconds

This is the publisher's version, also available electronically from “http://onlinelibrary.wiley.com”.Shallow seismic reflection surveys require dense spatial wave-field sampling, contributing to their high cost. To assess the feasibility of planting geophones automatically, we planted 72 geophones in approximately 2 s in a test line, using an 11-m-wide farm tillage tool as a planting device. Geophones were attached rigidly, at 15 cm intervals, to five pieces of heavy-duty channel iron bolted to the tillage-tool frame. Conventional comparison-line data collected about 75 cm away, parallel to the test line, were visually comparable with the seismic source 12 m distant. When the sources were placed 1 m from the geophones, a surface-wave mode was excited by the channel iron and detected by geophones in both lines. This mode exhibited a different phase velocity than that of the desired seismic body-waves and could be attenuated by frequency-wavenumber filtering. These results suggest that automatic geophone placement is feasible and could decrease shallow seismic surveying costs

Source-dependent frequency content of ultrashallow seismic reflection data

This is the publisher's version, also available electronically from "bssa.geoscienceworld.org".Seismic surveying within the upper few meters of the Earth's shallow subsurface requires a high-frequency source. To ascertain the important features of such sources, experiments were conducted at test sites in central and eastern Kansas using various impulsive seismic sources (4.5-kg hammer, 30.06 rifle, and .22-caliber rifle) to examine the effects of minimizing source energy on the frequency content of reflection data. Results indicate that the higher energy near-surface seismic-reflection sources (e.g., sledgehammer, large-caliber projectiles) lack some of the high-frequency energy exhibited by smaller sources, precluding the detection of reflection signal from ultrashallow depths (<3 m) at the sites tested. At the test site in eastern Kansas, the .22-caliber rifle yielded more energy above 250 Hz than either the sledgehammer or 30.06 rifle. At the test site in central Kansas, where three reflective interfaces shallower than 3 m exist, the .22-caliber rifle with subsonic ammunition yielded the largest amount of energy at frequencies above 300 Hz and produced the best data

Varying the effective mass of geophones

This is the published version. Reuse is subject to the Society of Exploration Geophysicists terms of use and conditions.Traditionally, acquiring seismic data has rested on the assumption that geophone mass should be as small as possible. When Steeples and coworkers in 1999 planted 72 geophones automatically and simultaneously with a farm tillage implement, the effective mass of each of the geophones was significantly increased. We examined how the mass of a geophone affects changes in traveltime, amplitude, frequency, and overall data quality by placing various external masses on top of 100‐Hz vertical geophones. Circular barbell weights of 1.1‐, 11.3‐, and 22.7 kg; an 8.2‐kg bag of lead shot; and a 136‐kg stack of barbell weights were placed on top of geophones during data acquisition. In addition, a very large mass in the form of a truck was parked on top of two of the geophones. Four seismic sources supplying a broad range of energies were tested: a sledgehammer, a .22‐caliber rifle, a 30.06 rifle, and an 8‐gauge Betsy Seisgun. Spectral analysis revealed that the smaller weights had the greatest effects on the capacities of the geophones to replicate the earth’s motion. Consequently, using geophones with a large effective mass as part of an automatic geophone‐planting device would not necessarily be detrimental to the collection of high‐quality near‐surface seismic data

Point mutations of human interleukin-1 with decreased receptor binding affinity

AbstractInterleukin-1 (IL-1) is a monocyte-derived polypeptide hormone that interacts with a plasma membrane receptor. We have used oligonucleotide-directed mutagenesis to construct mutant human IL-1 proteins. Three different point mutants in a unique histidine residue (position 30) exhibited varying degrees of reduced IL-1 receptor binding affinity, whereas point mutants at five other residues behaved normally. Structural analysis of these mutant proteins by nuclear magnetic resonance spectroscopy detected no (or only minor) conformational changes relative to wild-type IL-1. These data suggest that the unique histidine residue influ- ences the architecture of the receptor binding site on human IL-1

Seismic reflections from depths of less than two meters

This is the publisher's version, also available electronically from "http://onlinelibrary.wiley.com".Three distinct seismic reflections were obtained from within the upper 2.1 m of flood-plain alluvium in the Arkansas River valley near Great Bend, Kansas. Reflections were observed at depths of 0.63, 1.46, and 2.10 m and confirmed by finite-difference wave-equation modeling. The wavefield was densely sampled by placing geophones at 5-cm intervals, and near-source nonelastic deformation was minimized by using a very small seismic impulse source. For the reflections to be visible within this shallow range, low seismic P-wave velocities (<300 m/s) and high dominant-frequency content of the data (∼450 Hz) were essential. The practical implementation of high-resolution seismic imaging at these depths has the potential to complement ground-penetrating radar (GPR), chiefly in areas where materials exhibiting high electrical conductivity, such as clays, prevent the effective use of GPR. Potential applications of these results exist in hydrogeology and environmental, Quaternary, and neotectonic geology