Blocks of igneous rocks such as anorthosite and granite subjected at one end to uniaxial stress h... more Blocks of igneous rocks such as anorthosite and granite subjected at one end to uniaxial stress have been shown to emit a small but distinct excess amount of infrared (IR) light (Freund, F. T., et al, JASTP, 71, 2009). This anomalous IR emission arises from the radiative de-excitation of electron vacancy defects, which, upon stress-activation, flow into the unstressed portion and recombine at the surface. This non-thermal IR emission occurs in the 8 mum to 14 mum wavelength region. Field experiments are performed by slowly stressing large boulders and monitoring the IR emission in situ with a Bruker EM27 Fourier Transform Infrared (FTIR) spectrometer. The boulders are prepared by drilling four blind holes into the rock, 50-100 cm deep, in an array roughly parallel to, and behind, the surface from where the IR emission is monitored. Any debris and water is blown out of the boreholes with compressed air, and the rock is given time to dry and relax from drilling-induced stresses. The h...
The muzzle blast caused by the discharge of a firearm generates a loud, impulsive sound that prop... more The muzzle blast caused by the discharge of a firearm generates a loud, impulsive sound that propagates away from the shooter in all directions. The location of the source can be computed from time-of-arrival measurements of the muzzle blast on multiple acoustic sensors at known locations, a technique known as multilateration. The multilateration problem is considerably simplified by assuming straight-line propagation in a homogeneous medium, a model for which there are multiple published solutions. Live-fire tests of the ShotSpotter gunshot location system in Pittsburgh, PA were analyzed off-line under several algorithms and geometric constraints to evaluate the accuracy of acoustic multilateration in a forensic context. Best results were obtained using the algorithm due to Mathias, Leonari and Galati under a two-dimensional geometric constraint. Multilateration on random subsets of the participating sensor array show that 96% of shots can be located to an accuracy of 15 m or bette...
DESCRIPTION Stress-dependent voltage offsets from polymer insulators used in rock mechanics and m... more DESCRIPTION Stress-dependent voltage offsets from polymer insulators used in rock mechanics and material testing
This paper addresses a case study of the Dec. 22 2004, M6.4 San Simeon earthquake in California, ... more This paper addresses a case study of the Dec. 22 2004, M6.4 San Simeon earthquake in California, and compares both space and ground ELF signatures. Preliminary results of the satellite collections showed unique signals prior to and after the San Simeon quake, as well as several other large world-wide quakes. Ground collections were inconclusive since the closest 4 sensors of the available 35 sensors were located more than 60 km and 2 parallel fault traces away from the San Simeon quake epicenter.
There have been a number of reports of interesting electromagnetic (EM) signals detected prior to... more There have been a number of reports of interesting electromagnetic (EM) signals detected prior to large earthquakes, but the subsequent analyses have been hampered by insufficient instrumentation to cover large geographical areas, and enough data history to allow statistical analyses of potential "earthquake signatures". The EM data analysis requires that several basic questions be addressed: "What are the "normal" background signatures (both natural and man-made) for each instrument during non-earthquake days?" and "What are the statistically "unique" signatures associated with large earthquakes?" Both ground and space sensors are subjected to a wide variety of non-earthquake EM noise (geomagnetic micropulsations, SRS, Schumann Resonance and man-made EM noise). We first show the top-level strategy developed by QuakeFinder and our partners to collect large volumes of satellite EM data (DEMETER and QuakeSat), and ground EM data (from ...
A collaboration between QuakeFinder (Palo Alto) and NASA JPL utilized both ground and space instr... more A collaboration between QuakeFinder (Palo Alto) and NASA JPL utilized both ground and space instruments to observe a series of electromagnetic (EM) signals detected up to 2 weeks prior to the Oct 30, 2007 Alum Rock, California, M5.4 earthquake. These signals included Ultra Low Frequency (ULF: 0.01 to 12 Hz) pulsations that were detected with a 3 axis induction magnetometer located 2 km from the epicenter. The 1- 12 sec wide pulsations were 10-50 times more intense than 2 year normal background noise levels, and the pulsations occurred 10-30 times more frequently in the 2 weeks prior to the quake than the average pulse count for the 1.8 years prior. The air conductivity sensor at the same site saturated for much of the evening prior to the quake. The conductivity levels were compared to the previous year's average conductivity patterns at the site, and determined not to be caused by moisture contamination. The GOES-West weather satellite typically observes the west coast of Calif...
The common characteristics of the signal found in the 0.0025-0.025 Hz portion of the geomagnetic ... more The common characteristics of the signal found in the 0.0025-0.025 Hz portion of the geomagnetic spectrum are presented as measured by the CalMagNet high-resolution search coil network. Coherence, azimuth ratio, and timing of wave characteristics are depicted, showing their statistical variances, and potential for revealing residual local signals. The low coherence frequency band near 0.1Hz is compared with higher coherence signals at lower frequencies. Also presented are the results of comparing the characteristics of these signals around the time of earthquakes near the sensors as compared to control periods of data during non-earthquake periods.
Magnetic signal fluctuations that are potentially related to earthquake occurrences have been rep... more Magnetic signal fluctuations that are potentially related to earthquake occurrences have been reported for a number of years. Recently, short-duration pulses have been shown to occur in association with the Tacna, Peru M6.2 earthquake (May 6, 2010 02:42:47 UTC 18.02°S 70.53°W) and the Alum Rock M5.4 quake (Oct 31,03:04 UTC 2007 Lat 37.43N Long 121.78W), but since these are only 2 events, it is not clear how statistically significant these results are. Here, we use a novel algorithm to process several years of magnetometer data and automatically extract and classify any pulses that may have occurred. The list of pulses is then sorted according to clustering of parameters, typical noise sources are identified and removed, and the relation of the remaining pulses to earthquakes is examined on a statistical basis.
The DEMETER satellite, designed with the objective of investigating ionospheric phenomena before ... more The DEMETER satellite, designed with the objective of investigating ionospheric phenomena before earthquakes, measures the in-situ electron density at ~700 km height using a Langemuir probe. On the other hand, dual-frequency GPS data can be used to retrieve the Integrated Electron Content (IEC) along the ray path from ground stations to GPS satellites. We compare electron density data acquired by
ABSTRACT Using the triaxial search-coil magnetometer data in the ~ 1 Hz to 18 kHz frequency range... more ABSTRACT Using the triaxial search-coil magnetometer data in the ~ 1 Hz to 18 kHz frequency range from the low altitude (~710 km), high-inclination (~ 82°), DEMETER satellite, we perform a statistical search for magnetic signals that precede, coincide with, and succeed large earthquakes. We identify DEMETER passes that have occurred in a spatial region of radius ~ 3000 km around the epicenter, and -30 to +10 days around the time of large (M > 5) earthquakes, and perform a superposed epoch analysis of the signal amplitude in various frequency bands as a function of distance and time. This technique is useful in revealing weak signals that are associated in a systematic way with a given event, in our case seismic activity. We then subdivide the superposed epoch analysis plane into a "near" (0-1000 km) and "far" (2000-3000 km) regions relative to each earthquake, and compute the ratio R=near/far signals to test for any proximity effects. Finally, we subdivide all our data into a number of time periods, and perform the above analysis in each period, finally checking for repeatability amongst each of the separate periods. The above analysis is repeated under a variety of conditions, for example, only testing for shallow earthquakes, dividing the earthquakes into 3 types (normal/reverse/strike-slip), or only considering intense (M>6, 6.5, etc.) earthquakes. We present the results of our analysis with an extensive discussion of our methods.
ABSTRACT Pulsations are known to occur in the 0.005 - 0.1 Hz (period = 10 sec-150 sec) portion of... more ABSTRACT Pulsations are known to occur in the 0.005 - 0.1 Hz (period = 10 sec-150 sec) portion of the geomagnetic spectrum as a strong signal. They have been designated as Pc 3 &4, and prior work has sought to determine the structure of the magnetospheric standing waves for use in estimating density of the plasmasphere, etc. (Russell, et al. [1998]). Pc 3-4 characteristics also have held long interest for seismologists, as they are a form of interference when using digital seismometers to attempt measurements of long-period motion. Another recent source of interest in these pulsations stems from the announcement that some researchers have seen fluctuations in the geomagnetic signal associated with earthquakes. Reports of these anomalies have spanned frequencies in the range of 0.01 Hz, thus long term monitoring of Pc3-4 activity over California may be critical in defining the normal, background signal levels when looking for potential earthquake-related ULF signals. The deployment of high-resolution search coils in Quakefinder's CalMagNet in 2005, have allowed a much higher resolution and wider geographic distribution of measurements to study these complex signals. The analytical techniques of multi- channel coherence, wave analysis, and signal space separation provide unique characterizations of these signals, including latitude dependency. Progress in studying the geomagnetic signal using these techniques is presented, the signal estimator's design is shown, and future directions are discussed.
Since ultra-low frequency (ULF) magnetic anomalies were discovered prior to the 1989 Loma Prieta,... more Since ultra-low frequency (ULF) magnetic anomalies were discovered prior to the 1989 Loma Prieta, Ca. M7.0 earthquake, QuakeFinder, a small R&D group based in Palo Alto California has systematically monitored ULF magnetic signals with a network of 3-axis induction magnetometers since 2000 in California. This raw magnetometer data was collected at 20-50 samples per sec., with no preprocessing, in an
Blocks of igneous rocks such as anorthosite and granite subjected at one end to uniaxial stress h... more Blocks of igneous rocks such as anorthosite and granite subjected at one end to uniaxial stress have been shown to emit a small but distinct excess amount of infrared (IR) light (Freund, F. T., et al, JASTP, 71, 2009). This anomalous IR emission arises from the radiative de-excitation of electron vacancy defects, which, upon stress-activation, flow into the unstressed portion and recombine at the surface. This non-thermal IR emission occurs in the 8 mum to 14 mum wavelength region. Field experiments are performed by slowly stressing large boulders and monitoring the IR emission in situ with a Bruker EM27 Fourier Transform Infrared (FTIR) spectrometer. The boulders are prepared by drilling four blind holes into the rock, 50-100 cm deep, in an array roughly parallel to, and behind, the surface from where the IR emission is monitored. Any debris and water is blown out of the boreholes with compressed air, and the rock is given time to dry and relax from drilling-induced stresses. The h...
The muzzle blast caused by the discharge of a firearm generates a loud, impulsive sound that prop... more The muzzle blast caused by the discharge of a firearm generates a loud, impulsive sound that propagates away from the shooter in all directions. The location of the source can be computed from time-of-arrival measurements of the muzzle blast on multiple acoustic sensors at known locations, a technique known as multilateration. The multilateration problem is considerably simplified by assuming straight-line propagation in a homogeneous medium, a model for which there are multiple published solutions. Live-fire tests of the ShotSpotter gunshot location system in Pittsburgh, PA were analyzed off-line under several algorithms and geometric constraints to evaluate the accuracy of acoustic multilateration in a forensic context. Best results were obtained using the algorithm due to Mathias, Leonari and Galati under a two-dimensional geometric constraint. Multilateration on random subsets of the participating sensor array show that 96% of shots can be located to an accuracy of 15 m or bette...
DESCRIPTION Stress-dependent voltage offsets from polymer insulators used in rock mechanics and m... more DESCRIPTION Stress-dependent voltage offsets from polymer insulators used in rock mechanics and material testing
This paper addresses a case study of the Dec. 22 2004, M6.4 San Simeon earthquake in California, ... more This paper addresses a case study of the Dec. 22 2004, M6.4 San Simeon earthquake in California, and compares both space and ground ELF signatures. Preliminary results of the satellite collections showed unique signals prior to and after the San Simeon quake, as well as several other large world-wide quakes. Ground collections were inconclusive since the closest 4 sensors of the available 35 sensors were located more than 60 km and 2 parallel fault traces away from the San Simeon quake epicenter.
There have been a number of reports of interesting electromagnetic (EM) signals detected prior to... more There have been a number of reports of interesting electromagnetic (EM) signals detected prior to large earthquakes, but the subsequent analyses have been hampered by insufficient instrumentation to cover large geographical areas, and enough data history to allow statistical analyses of potential "earthquake signatures". The EM data analysis requires that several basic questions be addressed: "What are the "normal" background signatures (both natural and man-made) for each instrument during non-earthquake days?" and "What are the statistically "unique" signatures associated with large earthquakes?" Both ground and space sensors are subjected to a wide variety of non-earthquake EM noise (geomagnetic micropulsations, SRS, Schumann Resonance and man-made EM noise). We first show the top-level strategy developed by QuakeFinder and our partners to collect large volumes of satellite EM data (DEMETER and QuakeSat), and ground EM data (from ...
A collaboration between QuakeFinder (Palo Alto) and NASA JPL utilized both ground and space instr... more A collaboration between QuakeFinder (Palo Alto) and NASA JPL utilized both ground and space instruments to observe a series of electromagnetic (EM) signals detected up to 2 weeks prior to the Oct 30, 2007 Alum Rock, California, M5.4 earthquake. These signals included Ultra Low Frequency (ULF: 0.01 to 12 Hz) pulsations that were detected with a 3 axis induction magnetometer located 2 km from the epicenter. The 1- 12 sec wide pulsations were 10-50 times more intense than 2 year normal background noise levels, and the pulsations occurred 10-30 times more frequently in the 2 weeks prior to the quake than the average pulse count for the 1.8 years prior. The air conductivity sensor at the same site saturated for much of the evening prior to the quake. The conductivity levels were compared to the previous year's average conductivity patterns at the site, and determined not to be caused by moisture contamination. The GOES-West weather satellite typically observes the west coast of Calif...
The common characteristics of the signal found in the 0.0025-0.025 Hz portion of the geomagnetic ... more The common characteristics of the signal found in the 0.0025-0.025 Hz portion of the geomagnetic spectrum are presented as measured by the CalMagNet high-resolution search coil network. Coherence, azimuth ratio, and timing of wave characteristics are depicted, showing their statistical variances, and potential for revealing residual local signals. The low coherence frequency band near 0.1Hz is compared with higher coherence signals at lower frequencies. Also presented are the results of comparing the characteristics of these signals around the time of earthquakes near the sensors as compared to control periods of data during non-earthquake periods.
Magnetic signal fluctuations that are potentially related to earthquake occurrences have been rep... more Magnetic signal fluctuations that are potentially related to earthquake occurrences have been reported for a number of years. Recently, short-duration pulses have been shown to occur in association with the Tacna, Peru M6.2 earthquake (May 6, 2010 02:42:47 UTC 18.02°S 70.53°W) and the Alum Rock M5.4 quake (Oct 31,03:04 UTC 2007 Lat 37.43N Long 121.78W), but since these are only 2 events, it is not clear how statistically significant these results are. Here, we use a novel algorithm to process several years of magnetometer data and automatically extract and classify any pulses that may have occurred. The list of pulses is then sorted according to clustering of parameters, typical noise sources are identified and removed, and the relation of the remaining pulses to earthquakes is examined on a statistical basis.
The DEMETER satellite, designed with the objective of investigating ionospheric phenomena before ... more The DEMETER satellite, designed with the objective of investigating ionospheric phenomena before earthquakes, measures the in-situ electron density at ~700 km height using a Langemuir probe. On the other hand, dual-frequency GPS data can be used to retrieve the Integrated Electron Content (IEC) along the ray path from ground stations to GPS satellites. We compare electron density data acquired by
ABSTRACT Using the triaxial search-coil magnetometer data in the ~ 1 Hz to 18 kHz frequency range... more ABSTRACT Using the triaxial search-coil magnetometer data in the ~ 1 Hz to 18 kHz frequency range from the low altitude (~710 km), high-inclination (~ 82°), DEMETER satellite, we perform a statistical search for magnetic signals that precede, coincide with, and succeed large earthquakes. We identify DEMETER passes that have occurred in a spatial region of radius ~ 3000 km around the epicenter, and -30 to +10 days around the time of large (M > 5) earthquakes, and perform a superposed epoch analysis of the signal amplitude in various frequency bands as a function of distance and time. This technique is useful in revealing weak signals that are associated in a systematic way with a given event, in our case seismic activity. We then subdivide the superposed epoch analysis plane into a "near" (0-1000 km) and "far" (2000-3000 km) regions relative to each earthquake, and compute the ratio R=near/far signals to test for any proximity effects. Finally, we subdivide all our data into a number of time periods, and perform the above analysis in each period, finally checking for repeatability amongst each of the separate periods. The above analysis is repeated under a variety of conditions, for example, only testing for shallow earthquakes, dividing the earthquakes into 3 types (normal/reverse/strike-slip), or only considering intense (M>6, 6.5, etc.) earthquakes. We present the results of our analysis with an extensive discussion of our methods.
ABSTRACT Pulsations are known to occur in the 0.005 - 0.1 Hz (period = 10 sec-150 sec) portion of... more ABSTRACT Pulsations are known to occur in the 0.005 - 0.1 Hz (period = 10 sec-150 sec) portion of the geomagnetic spectrum as a strong signal. They have been designated as Pc 3 &4, and prior work has sought to determine the structure of the magnetospheric standing waves for use in estimating density of the plasmasphere, etc. (Russell, et al. [1998]). Pc 3-4 characteristics also have held long interest for seismologists, as they are a form of interference when using digital seismometers to attempt measurements of long-period motion. Another recent source of interest in these pulsations stems from the announcement that some researchers have seen fluctuations in the geomagnetic signal associated with earthquakes. Reports of these anomalies have spanned frequencies in the range of 0.01 Hz, thus long term monitoring of Pc3-4 activity over California may be critical in defining the normal, background signal levels when looking for potential earthquake-related ULF signals. The deployment of high-resolution search coils in Quakefinder's CalMagNet in 2005, have allowed a much higher resolution and wider geographic distribution of measurements to study these complex signals. The analytical techniques of multi- channel coherence, wave analysis, and signal space separation provide unique characterizations of these signals, including latitude dependency. Progress in studying the geomagnetic signal using these techniques is presented, the signal estimator's design is shown, and future directions are discussed.
Since ultra-low frequency (ULF) magnetic anomalies were discovered prior to the 1989 Loma Prieta,... more Since ultra-low frequency (ULF) magnetic anomalies were discovered prior to the 1989 Loma Prieta, Ca. M7.0 earthquake, QuakeFinder, a small R&D group based in Palo Alto California has systematically monitored ULF magnetic signals with a network of 3-axis induction magnetometers since 2000 in California. This raw magnetometer data was collected at 20-50 samples per sec., with no preprocessing, in an
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Papers by Clark Dunson