Networked system and method for passive monitoring, locating or characterizing activities
Systems and methods are provided for determining localization information for sources of seismic energy positioned below a ground surface. In accord with one series of embodiments, a method of determining localization information receives data from first seismic sensors in a first three dimensional array containing sensors emplaced below the ground surface and coherently processes the signals to provide three dimensional localization information that enables determination of an angle of arrival for a signal of interest. In combination with data from second seismic sensors in a second three dimensional array the method provides determination of a position in three dimensional space.
1. A system for determining localization information for a first energy source positioned below a ground surface based on sensed seismic signals associated with a first signal of interest (SOI) generated by the first energy source, the first SOI including first waveform components associated with a first design frequency for which phase velocity and wavelength of the first waveform components vary based on properties of media below the ground surface, the system comprising: a sensor subsystem including a first group of seismic sensors arranged in a first array emplaced below the ground surface, which sensors are responsive to sense seismic energy from the first energy source in a frequency range extending from 10 Hz to 2 kHz, and where, a plurality of the sensors in the first array are point sensors spaced apart in a three-dimensional distribution, where at least one subset of sensors in the first series of
sensors has a first separation distance that correlates with half the wavelength of a first waveform component in the first SOI associated with the first design frequency, and with respect to a horizontal plane extending along a direction parallel to a portion of the ground surface: sensors in the first array extend in a vertical dimension below the ground surface with the first separation distance between a first sensor in said one subset and a second sensor in said one subset; and
a processing subsystem coupled to receive seismic data acquired from sensors in the first array, the processing subsystem including a processor and storage media having computer instructions stored thereon to perform spatial coherent processing of said first waveform components associated with the first design frequency, where:
the coherent processing performed on seismic signals received from said at least one subset in the first series of sensors, determines a three dimensional angle of arrival of the first SOI from the first energy source to the first array.
2. The system of claim 1 where, the sensors in the first array are arranged as a three-dimensional bounded convex polytope with sensors at vertices of the polytope,
and the exterior surface of the convex polytope defining convex polygons, the length of whose edges correspond to sensor separations specified according to a design frequency.
3. The system of claim 1 including
a second subset of sensors having spacings between pairs of the sensors in said second subset rendering the coherent processing of said seismic signals responsive to waveform components associated with a second design frequency so that, when coherent processing is performed on seismic signals received from said second subset in the first series of sensor elements, a second three dimensional angle of arrival of a second SOI to the first array is determined; and
relative to one of said waveform components associated with the second design frequency, impinging on a first sensor in said second subset, and having a wavelength associated with the second design frequency, at the first sensor in said second subset, the first sensor is a point sensor, having maximum dimensions less than five percent of the wavelength.
4. The system of claim 3 where, with respect to the horizontal plane extending along the direction parallel to a portion of the ground surface:
sensors in the first array extend horizontally along and below the ground surface with a first separation distance between the first sensor in said second subset and a second sensor in said second subset; and
the first separation distance correlates with half the wavelength of a second waveform component in the second SOI associated with the second design frequency when the second waveform component impinges on the sensors in said second subset.
5. The system of claim 1 configured to determine localization information where:
the sensor subsystem includes a second group of seismic sensors arranged in a second array emplaced below the ground surface, which sensors are responsive to sense seismic energy from the first energy source in a frequency range extending from 10 Hz to 2 kHz; and the processing subsystem is coupled to receive seismic data acquired from sensors in the second array and execute computer instructions to perform coherent processing of said first waveform components associated with the first design frequency and acquired from sensors in the second array, where:
a second subset of sensors in the second series of sensors has spacings between pairs of the sensors in said second subset rendering the coherent processing of said seismic signals responsive to the first waveform components associated with the first design frequency, and the coherent processing performed on seismic signals received from said at least the second subset in the second series of sensor elements determines, a three dimensional angle of arrival of the first SOI from the first energy
source to the second array.
6. The system of claim 5 where:
the three dimensional angle of arrival of the first SOI from the first energy source to the first array is defined by a first beam vector which intersects a reference point of the first array and the first waveform components from the first energy source;
the three dimensional angle of arrival of the first SOI from the first energy source to the second array is defined by a second beam vector which intersects a reference point of the second array and the first waveform components from the first energy source; and
the processing subsystem includes storage media having further computer instructions stored thereon to provide location information for the first energy source based on intersection of the first and second beam vectors.
7. A method for determining localization information for a first energy source positioned below a ground surface based on sensed seismic signals associated with a first signal of interest (SOI) generated by the first energy source, the first SOI including first waveform components associated with a first design frequency for which phase velocity and wavelength of the first waveform components vary based on properties of media below the ground surface, the method comprising:
providing a sensor subsystem including a first group of seismic sensors arranged in a first array emplaced below the ground surface, which sensors are responsive to sense seismic energy from the first energy source in a frequency range extending from 10 Hz to 2 kHz, and where, a plurality of the sensors in the first array are point sensors spaced apart in a three-dimensional distribution, and at least one subset of sensors in the first series of sensors has a first separation distance that correlates with half the wavelength of a first waveform component in the first SOI associated with the first design frequency, and with respect to a horizontal plane extending along a direction parallel to a portion of the ground surface: sensors in the first array extend in a vertical dimension below the ground surface with the first separation distance between a first sensor in said one subset and a second sensor in said one subset;
providing a processing subsystem coupled to receive seismic data acquired from sensors in the first array, the processing subsystem including a processor and storage media having computer instructions stored thereon to perform spatial coherent processing of said first waveform components associated with the first design frequency; where
the coherent processing performed on seismic signals received from said at least one subset in the first series of sensors, determines a three dimensional angle of arrival of the first SOI from the first energy source to the first array.
8. The method of claim 7 further comprising arranging the sensors in the first array as a three dimensional bounded convex polytope with sensors at vertices of the polytope, and the exterior surface of the convex polytope defining convex polygons, the length of whose edges correspond to sensor separations specified according to a design frequency.
9. The method of claim 7 further comprising:
providing a second subset of sensors having spacings between pairs of the sensors in said second subset rendering the coherent processing of said seismic signals responsive to waveform components associated with a second design frequency so that, in coherent processing performed on seismic signals received from said second subset in the first series of sensor elements, a second three dimensional angle of arrival of a second SOI to the first array is determined; and
relative to one of said waveform components associated with the second design frequency, impinging on a first sensor in said second subset, and having a wavelength associated with the second design frequency, at the first sensor in said second subset, the first sensor is a point sensor, having maximum dimensions less than five percent of the wavelength.
10. The method of claim 9 further comprising:
with respect to the horizontal plane extending along the direction parallel to a portion of the ground surface:
arranging sensors in the first array to extend horizontally along and below the ground surface with a first separation distance between the first sensor in said second subset and a second sensor in said second subset; and
the first separation distance correlates with half the wavelength of a second waveform component in the second SOI associated with the second design frequency when the second waveform component impinges on the
sensors in said second subset.
11. The method of claim 7 further comprising:
providing, in the sensor subsystem, a second group of seismic sensors arranged in a second array emplaced below the ground surface, which sensors are responsive to sense seismic energy from the first energy source in a frequency range extending from 10 Hz to 2 kHz; and
configuring the processing subsystem to receive seismic data acquired from sensors in the second array and execute computer instructions to perform coherent processing of said first waveform components associated with the first design frequency and acquired from sensors in the second array, where:
a second subset of sensors in the second series of sensors has spacings between pairs of the sensors in said second subset rendering the coherent processing of said seismic signals responsive to the first waveform components associated with the first design frequency, and the coherent processing performed on seismic signals received from said at least the second subset in the second series of sensor elements determines, a three dimensional angle of arrival of the first SOI from the first energy source to the second array.
12. The method of claim 11 : where:
the three dimensional angle of arrival of the first SOI from the first energy source to the first array is defined by a first beam vector which intersects a reference point of the first array and the first waveform components from the first energy source;
the three dimensional angle of arrival of the first SOI from the first energy source to the second array is defined by a second beam vector which intersects a reference point of the second array and the first waveform components from the first energy source; and
the method includes providing location information for the first energy source based on intersection of the first and second beam vectors.