Abstract: An alarm assembly specifically designed to warn sleeping occupants within a dwelling structure as to the occurrence of earth tremors such as those caused by relatively serious earthquakes wherein an activating member is movably positioned relative to a supporting base and is sensitive to such earth tremors to the extent of being displaced within a predetermined range of movement and into activating engagement with a switching assembly also mounted on said base to cause operation and/or activation of preferably an audio alarm to awaken the sleeping occupants.

Abstract: An improved ocean bottom seismometer is disclosed wherein a skirted spherical configuration provides bottom weight and provides a sealed area for seawater ballast which may be ejected to provide positive buoyancy for retrieval.

Abstract: This invention relates to an integrated acoustic network system to provide warning of impending groundfall in underground mines. The system includes a plurality of geophones which derive acoustic signals by which the source of seismic disturbances is located, and an array of high frequency piezoelectric sensors which pick up signals from small ground disturbances which precede groundfall. A warning system is provided both at the scene of mining operations and at a central location of impending groundfall and of the location of its occurrence.

Abstract: In accordance with an illustrative embodiment of the present invention, a plug-in geophone case includes a body having an open top and a cavity that receives a seismic detector having positive and negative terminals, receptacles on opposite sides of said body for plugging the case into leader cables, a set of three connector pins molded in the case adjacent each receptacle, one end of each pin extending into a receptacle and the other end extending into a recess in the body adjacent one of said terminals, a cover plate for closing the open top of said case, and means for sealingly fastening a connector plug in each of said receptacles, said plugs and receptacles having mating means to prevent connection with the wrong polarity.

Abstract: Two sector-shaped pendulums are supported by crossed leaf springs at two axes on the same horizontal level respectively in a symmetrical manner so that each pendulum can swing about the axis thereof, sector-shaped surfaces of the pendulums being connected to each other by mutually-crossing flexible wires, each pendulum having a movable weight and a rigid extension so that a coiled spring connects the rigid extensions of the two pendulums, and each pendulum has a means for adjusting the center of gravity thereof by moving said weight and for adjusting the location of joints of said coiled spring.

Abstract: A seismic detector comprises a casing the lower part (10) of which is provided with a plurality of apertures (19). A hydrophone transducer (70) comprising an annular ceramic member provided with metallized surfaces (71,72) is mounted in the casing and defines with the casing an enclosure (65) which houses a geophone (60). The outer face (71) of the hydrophone transducer (70) is subject to the ambient hydrostatic pressure via the apertures (19). The bottom of the casing is provided with a protuberance (11) to which a spike (12) is attached. The seismic detector can work in both hydrophonic and geophonic modes.

Abstract: A ferrite transformer is coupled between a two-wire array of geophones or other suitable vibration detectors (such as hydrophones). An oscillator is coupled across the secondary of the transformer in order to provide a carrier on which the output of the array may be modulated. A low level leakage current appears in the array so that a continuity test may be conducted to monitor the line for opens and shorts and to detect the operativeness of system components. The modulated output of the transformer is connected to a signal processing system.

Abstract: An electronic detection system for detecting intruders employs a transmisn line as a sensing element. In one embodiment the transmission line is a modified surface-wave transmission line, for example, a Goubau line, which is positioned about the perimeter of the area to be protected. An intruder in the field of the line causes an RF reflection back toward the source, which reflection may be detected by Doppler range-gating techniques. In other embodiments of the invention the transmission line is an insulated, twisted wire pair or a deformable transmission line. In some instances, the transmission line may be replaced with an active or passive pressure line.

Abstract: A small-sized, high sensitivity seismograph comprising a first seismometer for detecting left-right ground motions, a second seismometer for detecting up-down ground motions, two sets of protective device for preventing the seismographic detectors from damage due to excessive motions, an alarm system, and an adjustable device for adjusting the sensitivity of the alarm system. All of the above-described devices are provided in a case.

Abstract: An alarm system is provided for detecting a seismic tremor and for generating an audio and/or visual alarm signal which varies depending upon the magnitude of the seismic tremor. In the preferred form of the invention, the alarm system comprises a free running oscillator having a pair of terminals the capacitive value across which controls the frequency of the oscillator. A fixed oscillator plate is electrically connected to one terminal while a variable position oscillator plate is electrically connected to the other terminal and has an inertial mass secured to it. A spring positioned between the plates urges the variable position capacitor plate away from the fixed plate but still enables the variable position capacitor plate to move in response to a seismic tremor thus varying the capacitive value between the terminals and the frequency of the oscillator. The output from the oscillator is coupled through a phase locked loop circuit which tracks the oscillator output.

Abstract: A vertical seismometer comprises a horizontal boom 2 carrying a mass 1 frictionlessly pivoted about a horizontal axis 3. The boom is supported by a pre-stressed vertically extending flat spring 4 having one end rigidly attached to the boom adjacent to and intersecting this axis so that movement of the boom applies a turning moment to the flat spring at its attachment end. A further pre-stressed flat spring 5 pivoted at right angles to the other end of the first-mentioned flat spring has its other end rigidly connected to the frame 13 of the seismometer and applies a constant force along the longitudinal axis of the latter spring towards the end attached to the boom.

Abstract: A method of locating near-surface underground chambers, rooms, caves, pits, tubes, faults in surface rocks, and the like, using acoustic techniques is disclosed. For mapping large areas, a survey grid for transmitter transducer placement first is laid out over the area of interest.A transmitting transducer is coupled to the bedrock at one of the grid sites, and acoustic waves are generated in the earth by operation thereof. Portable acoustic receiving means, including a receiving transducer, are used to detect acoustic waves from the transmitter at a plurality of receiving sites surrounding the transmitting station. Transmitted acoustic waves from the transmitting site received by the receiving transducer are converted to electrical signals by the receiving transducer and recorded for subsequent use. Following operation of the receiving means at each receiving site surrounding the transmitter transducer, the received signals are compared to determine any differences in their magnitudes.

Abstract: An omnidirectional hydrophone using particles suspended in a liquid acoustically coupled to a conducting environment for detecting acoustic waves by providing scattering of internally generated electromagnetic radiation from particles driven by the acoustic waves.

Abstract: A seismograph pickup for use at the bottom of the sea, comprises a detector, a frame, detachable ballast, and a sealed and water-tight container mounted on the frame. The container floats for bringing the pickup to the surface when the ballast is detached. The detector is outside the container so that it may be deposited on the sea bed. The detector is connected to the container by means of an electric transmission cable and a mooring cable. The container includes a power source and means for recording signals delivered by the detector. The invention is also concerned with means for supporting the detector on the frame and for unhooking it when the detector is released.

Abstract: A method and apparatus for improved detection of reflected seismic energy through detection of air pressure variations in air above an air/earth surface interface. One form of apparatus suitable for detection in air of seismic energy waves emanating from beneath the earth surface consists of supporting a collecting reflecting member over a designated earth surface site and detecting air pressure variations at a focal point within the reflector member; and, thereafter, transmitting or conducting the reflected seismic energy indications for processing in accordance with the seismic energy source requirements to obtain seismic energy reflection data for the particular locale.

Abstract: An optical seismograph which functions to measure the relative movement of a beam of electromagnetic waves connected to the extremities of a plurality of pendulums and includes a collimated source which delivers a parallel beam of electromagnetic waves and a plurality of pendulums whose oscillation paths are perpendicular to one another, means fixed in relation to the electromagnetic wave beam direct the luminous beam on the heavy extremities of the various pendulums; and photoelectric means to measure the position variations of the extremities of the pendulums in relation to the electromagnetic wave beam. The seismograph is suitable for the detection of earthquakes.

Abstract: A fluid film levitated horizontally oriented disc is self-centering and floating above another similar mating surface stationary disc. A means for varying the natural period of free oscillation of the levitated disc within the normal earthquake band of frequencies and a means for damping out such free oscillations along with a means for transducing positional differences between the discs into signals wherein earth tremors arriving from any horizontal direction may be recorded.

Abstract: The transducer unit includes a rigid hollow casing. The casing defines through its cylindrical wall a plurality of sound-transmitting windows. A hydrophone having an elastomer core is removably positioned in the bore of the casing opposite to the windows. A pressure transducer element is embedded inside the core. The core is slightly compressed so as to form plugs for the windows.

Abstract: A detection system for indicating the presence of motorized equipment in a esignated area having an acoustic sensor, a seismic sensor and an acoustic signal transmitter. The seismic sensor output, processed to discriminate against vibrations of short duration, is fed, along with the acoustic sensor output, to an "ANDing" circuit which gates the acoustic transmitter. The acoustic sensor output is passed to the transmitter only during coincidence of seismic and acoustic detection.

Abstract: A mechanically resonant ground motion sensor having a frequency response which is "tuned" to discriminate between applied vibrational forces which are destructive and those which are not. The basic operating principle of the sensor is that of an oscillating mass whose dynamic response to applied forces takes the form of viscously damped harmonic motion. The disclosed embodiments include a horizontal ground motion detector based on the movement of a pendulum in a viscous fluid and a vertical ground motion detector utilizing a vertically sprung dashpot cylinder moving through a viscous fluid. The detector is tuned to trigger a tripping mechanism in response to accelerations above a threshold value and within the critical range of destructive frequencies.

Abstract: A remote troop movement detector comprising a common detector assembly or nister including a microphone and a seismometer together with a power supply and a transmitter circuit, formed to combine to adapt to various deployment situations. In one of its embodiments the detector canister is combined with a flotation collar and an anchor for waterborne deployment, in a second embodiment the canister is combined with a drag plate and a ballasted forward spike to form an aerodynamically stable configuration having a thin metal cone frustum intermediate the spike and the assembly for limiting and attenuating the ground penetration impact following an airdrop, and in a third embodiment the assembly is combined with a narrow tip for manual implantation.

Abstract: A method of seismic exploration is disclosed wherein an explosive charge is placed in a hole in the ground and wherein a detector is placed in a second hole spaced away from the first hole. The detector is mounted in the bottom of the hole by using an adherent base. The mouth of the hole is sealed to form a quiescent volume in the hole for the detector. Thereafter, the explosive charge is discharged and the output of the detector is recorded.

Abstract: This invention relates to a land seismic exploration method and apparatus employing a plurality of elongated tubes each having a flexible wall for containing a volume of liquid explosive therein. Each tube is adapted to be detachably connected to either a detonating device for exploding the liquid explosive therein thereby creating a seismic explosion, or to a pressure transducer for monitoring the pressure changes in the liquid explosive caused by the detected seismic pressure waves.

Abstract: New and improved apparatus and method for seismic exploration on land transports sensing geophones with a flat, lightweight, towing medium or sheet which conforms to the earth's surface. The geophones are mounted on sleds attached to the towing medium by strips or members of resilient material which isolate and decouple the geophone from vibrations and the like induced, sensed, or transmitted by the towing medium. The resilient members enable the geophones and sleds to continually maintain contact with the earth's surface over irregularities in the surface to provide good ground coupling for more accurate seismic exploration results. Plural or multiple towing mediums may be coupled together and towed into place for use in accordance with the desired geophone array to be used.

Abstract: This invention relates to seismic transducer assemblies for converting compressional wave motion or acoustic energy into electric energy in a fluid medium such as is encountered in marshy terrains. It also relates to an improved method of manufacturing such transducers. The transducer includes a rigid hollow casing having a conical end cap to facilitate planting the casing into the ground. At least one pressure transducer element is mounted in the casing. A water-impervious, pressure-transmitting, insulating core fills the casing's cavity. The material rigidly holds the transducer in place and allows transfer of pressure energy from the fluid medium in which the transducer assembly is submerged, to the inner surfaces of the transducer element.