Technical Resources

Publications

Ground motions for induced earthquakes in Oklahoma
Bulletin of the Seismological Society of America 2017
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We examine ground motions for a sequence of earthquakes in Oklahoma, where assessment of hazard contributions from induced seismicity is of particular interest. We aim to empirically calibrate a model‐driven equation that was derived for central and eastern North America (CENA), so that it will match the observed ground motions of the 2011 Prague, Oklahoma, sequence. We first show that ground motions in Oklahoma decay at a rate similar to the average attenuation observed in the stable continental region of CENA. We then search for any needed adjustments to the CENA source model to match ground motions from the induced seismicity sequence that occurred near Prague in 2011. An interesting feature noted in the ground‐motion analysis is that the stress parameters (Δσ) for the Prague mainshock events (M≥5) are notably higher than those for aftershocks. Moreover, the stress parameter that characterizes the high‐frequency ground‐motion decays in both time and space relative to the three largest events. The largest events in the Prague sequence have similar source parameters to natural CENA events of the same magnitude and focal depth, but their aftershocks have weaker motions.

Constraints on the near-distance saturation of ground-motion amplitudes for small-to-moderate induced earthquakes
Bulletin of the Seismological Society of America 2016
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We use a rich database of ground-motion amplitudes from shallow induced earthquakes of moment magnitude (M) 1.5 to 3.5 recorded at close distances in the Geysers region of California (the GEISER project database) to constrain the effective depth parameter for small events. We show that the effective depth parameter attains a value near 2 km for shallow events, at M =3; it reduces to smaller values for M <3 and gradually increases to larger values for M >3. We explore the implications of the new constraints on effective depth for induced seismicity GMPEs. We compare a ground-motion model that considers appropriate near-distance scaling to recorded ground motions from induced events in different environments, including Oklahoma and California. We find that ground motions from induced events in California are in good agreement with the GMPE of Atkinson (2015), while those in Oklahoma, for the larger events, are in good agreement with the GMPE of Yenier and Atkinson (2015) for central and eastern North America.

Direct burial broadband seismic instrumentation that are rugged and tilt tolerant for polar environments (Poster)
EGU 2016
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The need to densify observations in ice-covered regions with difficult and limited logistics led to specifications being developed for polar hardening a hybrid family of instruments that can operate at -55C autonomously with very little power, with high tilt tolerance for unstable ice and snow conditions. After one year of testing in the Antarctic at South Pole Station and McMurdo, the Meridian Compact and Meridian Compact Posthole seismic systems have been found to reduce the bulk of a complete station by one-half for the medium-band systems and greatly simplify installation.

Feasibility of tilt measurement using seismometer mass position data
SSA 2016
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In this study, we examined the effect of velocity model complexity and network density on location accuracy and uncertainty. We find that velocity model complexity plays an important role in focal depth accuracy, especially when distinct high and/or low velocity layers in the velocity model produce non-unique travel times for first arriving P and S waves. Our results highlight the importance of designing seismic networks to ensure that network density and station placement account for travel time profiles in the depth range of interest.

 
Microseismic monitoring using a sparse surface network of broadband instruments: Western Canada shale play case study
AGU 2016
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We provide a hydraulic fracture (HF) monitoring case study that compares the data set generated by a sparse local surface network of broadband seismometers to a data set generated by a single downhole geophone string. The resulting surface event catalog shows a very weak spatio-temporal correlation to HF operations with only 43% of recorded seismicity occurring during HF stages times. A cost-benefit analysis of the two monitoring methods shows that although the downhole array recorded ten times as many events, the surface network provides a more coherent delineation of the underlying structure and more accurate magnitudes for larger magnitude events. We attribute this to the enhanced focal coverage provided by the surface network and the use of broadband instrumentation. The results indicate that sparse surface networks of high-quality instruments can provide rich and reliable datasets for evaluation of the impact and effectiveness of hydraulic fracture operations in regions with favorable surface noise, local stress and attenuation characteristics.

Multi-use seismic stations for earthquake early warning (Poster)
AGU 2016
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Recent advances in instrumentation and processing techniques have made feasible the concept of a multi-use seismic station in which strong-motion and weak-motion seismometry are both cost-effectively served without compromising the performance demands of either. We present a concept for a multi-use seismic station that cost-effectively meets the needs of both earthquake early warning and high-quality seismic research. Combining two sensors into one effectively adds broadband capability to a station without increasing the already optimized site footprint, preparation and management costs associated with shallow direct-burial installations. The combined sensors also complement each other, simplifying and speeding installation. A dual-use 6-channel digitizer simultaneously provides two sets of independently processed streams from both sensors, one set optimized for low-latency earthquake warning, and the other set for high quality seismic research purposes. Such a dual-use seismic station can serve both seismic research and civil warning infrastructure objectives without adding significantly to the cost of a single-use station, while increasing the utility for all users of the station’s data.   

Potential applications of an integrated seismic, tilt, and temperature instrument (Poster)
EGU 2016
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Mass position changes with tilt (due to gravity) and temperature (due to the temperature coefficient of the springs). Mass position is typically recorded with low resolution as a state-of-health measurement for a seismometer, however an optimized output circuit for high-resolution mass positions fed to a 24-bit digitizer enables the derivation of simultaneous seismic, tilt and temperature datasets from a single instrument, for applications such as volcano and reservoir monitoring.

 
Prediction of earthquake ground motions in western Alberta (Poster)
SSA 2016
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We develop a suite of ground-motion prediction equations (GMPEs) for earthquakes in western Alberta, where seismic hazard contributions from induced events are of particular interest. The available ground-motion data is limited for deriving a robust predictive model in the magnitude range of engineering interest (M>4). We adopt two alternative published predictive models in order to ensure seismologically informed predictions for moderate-to-large magnitudes. We determine model adjustments for the regional source and attenuation attributes for each model using the referenced empirical approach, then provide two alternative GMPEs that are fully adjusted for observed motions in western Alberta and are applicable for wide ranges of magnitude and distance.

 
Sources of latency and associated design trade-offs in earthquake early warning systems (Poster)
EGU 2016
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Low latency is a key contributor to the success of earthquake early warning (EEW) systems. There are several points where delay is introduced between the instant in time that a digitizer produces a set of samples across its analog sensor channel inputs and the point at which the corresponding data reaches its destination for EEW. These points of delay arise out of software, mathematical, and networking as well as physical constraints imposed upon the digitizer and associated communication systems. System designs must account for tradeoffs between latency and resource (CPU) utilization, which has an effect on power consumption, and communication network bandwidth. Designers of seismological instrumentation used for EEW deployments must keep these trade-offs in mind and make careful implementation choices to minimize delay. System integrators and network operators must be fully aware of latency and its contributors in order to make the right configuration choices when commissioning EEW systems to ensure the lowest possible latency without compromising the accuracy of the early warning data product.

Discrimination of earthquake and blast seismicity in western Alberta
AGU Poster 2015
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We present a preliminary study on earthquake versus blast discrimination in western Alberta using normalized cumulative Arias intensities recorded at regional distances (>50km). Normalized intensities are evaluated after the expected shear-wave arrival to highlight the differences in ground motions following the P coda. Normalized intensities show maximum discrimination between blasts and earthquakes at near-regional distances (50-100km), for wide ground-motion windows. Using area under curve (AUC) analysis of average intensity profiles, confirmed and suspected blast clusters can be discriminated from confirmed earthquakes.

Earthquake frequency-magnitude distribution and fractal dimension in northern California
SSA 2015
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This study shows how the heterogeneity of seismogenic volumes can lead to differences in the fractal dimension (D-value) and the slope of the frequency-magnitude relationship (b-value) as well as demonstrate the correlation in the temporal variation of these two parameters and the time of large magnitude earthquakes. Local distribution of b and D values, as well as their ratio, reveal information about geological complexity and changes in the stress level in the region of study. Our results confirm that monitoring variations in b and D values as well as their ratio in time and space can be used to effectively identify earthquake clusters and also as a potential large earthquake precursor.

Installation techniques and network performance (Poster)
EGU 2015
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We present example simulations of array performance illustrating Mc for local and regional arrays using different installation depths. Models of typical noise in different depth ranges were derived by averaging background seismic PSDs from various Nanometrics projects throughout North America, representative of areas with limited overburden thickness (< 15 m) as commonly found in post-glacial environments around the world. Noise performance improving with depth is frequency dependent, so the benefit of depth depends on the band of interest of seismic events as a function of distance and magnitude.

 
Investigating the relationship between velocity model complexity and location accuracy
SSA 2015
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In this study, we examined the effect of velocity model complexity and network density on location accuracy and uncertainty. We find that velocity model complexity plays an important role in focal depth accuracy, especially when distinct high and/or low velocity layers in the velocity model produce non-unique travel times for first arriving P and S waves. Our results highlight the importance of designing seismic networks to ensure that network density and station placement account for travel time profiles in the depth range of interest.

Comparison study between vault seismometers and a new posthole seismometer (Poster)
EGU 2014
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We undertook a comparison study between the highest-performing vault seismometers and a new broadband posthole seismometer in a down-hole installation at different depths. We conducted a spectral analysis and generated PSD plots, and found that the burial of a seismometer results in a reduction of observed site noise that increases with depth of the seismometer, particularly on the horizontal components. This effect is observed for both high and low frequency data. Additionally, we compared the data for selected seismic events observed at both a vault seismometer and a posthole seismometer at the same location.

 
Downhole seismometers
Encyclopedia of Earthquake Engineering 2014
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The first section reviews the different types of downhole seismometers. The second section provides an overview of seismic noise sources and their impact on downhole installations. The last section discusses the downhole installation methods. There are three main motivations for deploying seismometers in a downhole environment. The first is to provide quieter seismic noise environment to improve signal-to-noise ratios. The second motivation is to lower the cost of deployment of a seismic station. The third motivation is to reduce the environmental impact and land use costs by minimizing the physical footprint of a seismic station.

Performance expectations for the Transportable Array in Alaska: Modeling magnitude of completeness and location accuracy (Poster)
SSA 2014
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The EarthScope transportable array began deployment in Alaska in 2014. Using a tool we developed for modeling the performance of microseismic monitoring arrays (which can also be applied to regional arrays), we modeled three significant array configurations: existing stations, the proposed transportable array and a hypothetical permanent array.

 
Principles of broadband seismometry
Encyclopedia of Earthquake Engineering 2014
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There are many different types of instruments which can be used to detect ground motion. Broadband seismometers belong to a class of sensors called inertial sensors. In contrast, methods of sensing ground motion such as strainmeters and Global Positioning Systems (GPS) are not considered inertial sensors. In this entry the principles of operation of broadband seismometers are discussed and contrasted with those of passive seismometers. The criteria for selecting a seismometer are discussed. Particular attention is paid to noise-generating mechanisms, including self-noise generated within the sensor, environmental sensitivities, and installation-related noise

Seismic network performance estimation: Comparing predictions to observation from an earthquake catalogue (Poster)
AGU 2014
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We compare predictions of network performance to observations made from an earthquake catalogue. We estimateeventspectra using Brune modeling andstation noiseto predict the magnitude of completeness for a network. We compare the predicted magnitude of completeness to an earthquake catalogue for the network. We use the maximum curvature method to assess the magnitude of completeness observed in the catalogue. We find that predicted and observed magnitude of completeness agree reasonably well, with the observed result being consistently lower than the predicted.

 
Symmetric triaxial seismometers
Encyclopedia of Earthquake Engineering 2014
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Of the class of seismic instruments measuring ground motion known as triaxial seismometers, most provide three signal outputs that represent mutually orthogonal motions in the East, North, and Vertical (or X, Y, and Z) directions. Of these, some are designed with three independent internal sensors that are respectively sensitive to motions in the three XYZ directions, and so directly measure the single vertical and two horizontal motion degrees of freedom. Some triaxial seismometers use a different configuration known as a Galperin arrangement, also known as a “symmetric triaxial” or “homogeneous” design. In the Galperin configuration, the sensing elements are also arranged to be mutually orthogonal, but instead of one axis being vertical, all three are inclined upwards from the horizontal at precisely the same angle, as if they were aligned with the edges of a cube balanced on a corner. The operational principles of a design based on the Galperin configuration have many similarities as well as some important differences relative to one based on the conventional XYZ arrangement. The Galperin configuration presents some significant benefits for the users, owners, andmanufacturers ofseismometers thatusethis topology,aswellasimplying sometrade-offsusers should be aware of. Benefits of a symmetric triaxial seismometer include being able to more easily distinguish external noise sources from internal ones, that mass centering does not compromise mutual orthogonality of the three axes, assurance of well-matched responses of the three outputs, and ability to achieve higher performance in smaller packages. A trade-off made by the Galperin approach is that unlike conventional XYZ seismometers that can suffer the failure of one axis element while continuing to provide valid output signals for the remaining two directions, all elements in a symmetric triaxial system must function for any of its XYZ outputs to be valid. The first modern broadband seismometer to be based on a Galperin configuration was the Streckeisen STS-2, an observatory-grade vault instrument introduced in 1990. Nanometrics introduced a symmetric triaxial seismometer with a 240 s lower corner period, the Trillium 240, in 2004. There are now a wide variety of symmetric triaxial seismometers available including models designed for borehole, posthole, ocean bottom, and vault installation and ranging from ultracompact to the large form factors.

 
Comparison of a waveform cross-correlation method to a traditional STA/LTA picker: Application to the Crooked Lake sequence near Fox Creek, Alberta (Poster)
AGU 2013
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We apply a cross correlation-based detection method to a sequence of events at Crooked Lake near Fox Creek, Alberta occurring in early December of 2013, using the largest event in the sequence (ML=3.9) as a template. We compare the performance of the cross-correlation technique with a traditional STA/LTA trigger. We find that the STA/LTA method identifies 24 events while the template matching method identifies 113 events including all of the 24 STA/LTA events. We estimate that the cross-correlation method offers an improvement in detection threshold of roughly 0.8 magnitude units. We explore empirical fits to the observed distribution of cross correlation coefficients.

 
A trawl-resistant ocean-bottom seismometer (Poster)
2011
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Long-term ocean-bottom seismometer (OBS) deployments are difficult on continental shelves and other shallow regions because of the hazard from bottom trawling.  The OBS lab at Lamont-Doherty Earth Observatory (LDEO) has developed a trawl-resistant OBS that is designed to resist and deflect bottom-trawling equipment.  Fifteen trawl-resistant OBSs were deployed in July 2011 from the R/V Wecoma as part of the Cascadia Initiative.

White Papers

Comparison study between vault seismometers and a new posthole sesimometer
Year: 2013
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Surface vault broadband seismometers have typically yielded good results on the vertical, but have been unreliable and noisy on the horizontal. There are several reasons for this issue, including inherent problems with surface tilt noise and thermal stability. A comparison study was undertaken between the highest performing vault seismometers and a new broadband Posthole seismometer in a down-hole installation, at different depths and in various environments at stations in North America ranging from remote locations in Alaska to a noisy urban area. In the remote and urban studies, a spectral analysis was conducted and PSD plots were generated, the results of which will be provided in detail in the paper. This paper will discuss all of the results from these installations as well as the various installation techniques at these locations. 

Measuring the dynamic range of a Nanometrics acclerograph
Year: 2013
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The dynamic range of an accelerometer or accelerograph (an accelerometer with a built-in digitizer) can be measured and plotted as a function of frequency, by comparing the amplitude of instrument selfnoise to the clip-level amplitude at specific frequencies.  This technical note outlines an appropriate procedure, and is consistent with the methodology used by the U.S. Geological Survey (USGS) in measuring accelerometers to determine if they comply with Advanced National Seismic Systems (ANSS) specifications.  The derivation of the formulae is discussed in a theory section.  The final section shows plots derived from an actual example data set recorded from a TitanSMA accelerograph to illustrate the procedure. 

Nanometrics posthole seismometers
Year: 2012
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The Nanometrics Trillium 120 Posthole (Trillium Posthole) seismometer is designed for subsurface installation to optimize seismic performance while minimizing the cost and logistics of site setup. This paper features an analysis of installation techniques in typical environments, and for each of these environments, provides compelling results from independent and internal studies that illustrate the advantages of buried instruments such as the Trillium Posthole. 

Case Studies

Title Authors Year
  Download *New temporary broadband array with open public data set will facilitate new research IRIS PASSCAL, Sweetwater, TX Nanometrics 2015
  Download Excellent results in Grafenberg, Germany. Next generation Trillium Borehole installed at the GRFO station site. Nanometrics 2015
  Download Mission Critical Seismic Network CQ Net: Republic of Cyprus Nanometrics 2015
  Download Monitoring Natural and Induced Seismicity. Horn River Basin, Northern BC, Canada Nanometrics 2015
  Download Direct Burial Posthole Sites in Yukon Yield Excellent Results Nanometrics 2013
  Download Real-time Monitoring with High Performance Seismic Array, Bayou Corne Sinkhole Louisiana, USA Nanometrics 2012

Brochures & Datasheets

Broadband Seismometers
Download Trillium Borehole Seismometer
Download Trillium Compact All-Terrain Seismometer
Download Trillium Compact Ocean Bottom Seismometer
Download Trillium Posthole Seismometer
Digital Seismometers
Download Meridian Compact Digital Seismometer
Download Meridian Compact Sensor Plot
Strong Motion Sensors
Download Strong Motion Instrumentation
Download Titan Accelerometer
Download Titan Posthole
Software
Download Apollo Server
Download Bulletin Hydra
Download SQLX Quality Assessment Tool (a)
Download SQLX Quality Assessment Tool (b)
Communications
Download Libra VSAT System
Additional Resources
Download Induced Seismicity and Geothermal Monitoring
Download Plants Seismic Monitoring and Surveys
Download Tsunami Early Warning System