Author: QuakeLogic

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QuakeLogic

Curated QuakeLogic articles, application notes, and technical explainers for engineering teams.

Earthquake EngineeringStructural Health MonitoringEarthquake Early WarningSeismic SensorsInfrasound MonitoringShake TablesData Acquisition SystemsInfrastructure Monitoring
Areas of expertiseSeismic monitoring, structural health monitoring, testing systems, data acquisition, and applied engineering education.
Data center seismic monitoring system with seismic sensors protecting critical server infrastructure.
Technical Note

Data Center Seismic Monitoring

Data center seismic monitoring helps protect critical infrastructure from earthquake-related risks. Data centers depend on stable equipment, reliable power, and continuous network access. Even moderate ground movement can affect sensitive systems, especially...

Nov 6, 20267 min read

How to Install an Accelerograph and GPS Antenna in a Building

Accelerograph bolted to a concrete floor inside a building with GPS antenna cable routed to a window

In short: Accelerograph installation inside a building starts with a site near the structural core, away from HVAC and machinery, ideally bolted level to the floor in a NEMA enclosure with 1 ft (0.3 m) of clearance. Place the GPS antenna with a clear sky view at a window or outdoors, route its cable without sharp bends, power through a grounded surge protector, then verify GPS lock and test recording.

Overview

This guide outlines the comprehensive steps for installing an accelerograph and its accompanying GPS antenna within a building structure. It covers mounting procedures, necessary clearances, and accessibility considerations to ensure optimal performance and ease of maintenance.

Tools and Materials Required

  • Drill and drill bits
  • Mounting brackets and hardware (screws, anchors, etc.)
  • Screwdriver
  • Level
  • Measuring tape
  • Cable conduits (if necessary)
  • Sealant (for outdoor installations)

Pre-Installation Planning

  1. Location Selection: Choose a location that minimizes vibrations from non-seismic sources (e.g., heavy machinery, and HVAC systems). Ideally, the accelerograph should be positioned close to the building’s structural core. It is better to install it on the floor inside an NEMA enclosure.
  • GPS Antenna Placement: The GPS antenna requires a clear view of the sky to maintain satellite communication. It should be placed on or near a window sill or mounted externally with a clear path to the sky, avoiding obstructions such as tall buildings or heavy foliage. The GPS provides absolute timing to the instrument for time-stamping of the waveforms recorded.
  • Accessibility: Ensure the installation site is easily accessible for maintenance and data retrieval. An access panel or removable ceiling tiles are recommended for indoor installations.
  • Clearances: Maintain at least 1 foot (~0.3 meters) of clearance around the accelerograph for ventilation and to ensure unobstructed access.

Installation Steps

  1. Mounting the Accelerograph:
  • Use the measuring tape and level to mark the drill point for the mounting anchor ensuring the accelerograph will be level.
    • Drill a hole at the marked point and insert the anchor.
    • Secure the mounting anchor with a screw.
    • Attach the accelerograph to the mounting anchor following the manufacturer’s guidelines.

Example of floor mounting

In the following picture, you can see a floor-mounting installation of a unit with an internal sensor with the use of a bolt in the concrete.

accelerograph install 1 for "Installation Instructions for Accelerograph with GPS Antenna Inside a Building"

Drawing is courtesy of SARA

The leveling pads do not necessarily need the counter-lock paddle (not drawn in the figure), even if it is always good to have. They would work in a counteraction, so the paddles shall be adjusted forcing the sensor to go up, while the bolt keeps it fixed down.

accelerograph install 2 for "Installation Instructions for Accelerograph with GPS Antenna Inside a Building"

Photo is courtesy of SARA

The same principle will work for wall and ceiling installations as follows.

Example of wall mounting or ceiling

If the unit needs to be mounted in buildings, it often requires a vertical or ceiling-flipped installation. In these cases, is essential to use the central key-hole hooking slot.

accelerograph install 3 for "Installation Instructions for Accelerograph with GPS Antenna Inside a Building"

Drawing is courtesy of SARA

In both cases, especially for mounting equipment over 1 meter of elevation we absolutely recommend the use of a safety chain or steel cord.
It can be anchored to any suitable threaded hole. If necessary and appropriate you may decide to use 2 or more threaded holes to anchor the safety cord.
All safety retention devices must be checked every year. To be on the safer side a shaft or a large steel baseplate could be used instead of the use of a dowel.

Appropriate heavy-load dowel and proper bolt are necessary to anchor this way, also depending on type of material the wall is made of, concrete, bricks, etc.

The bolt head should be of 12 mm, maximum of 14 mm to allow a proper leveling degree of freedom. The diameter of bolt stem should be not less than 8 mm for wall or ceiling mounting.

NOTE – 1: It is very important to have a safety bonding for the wall and ceiling mount and check the tightness of it periodically else vibrations will be wrongly measured.

NOTE – 2: Do not overtight the feet else the case will be damaged.

  • Installing the GPS Antenna (if applicable):
  • If mounting externally, ensure the antenna is positioned securely with a clear view of the sky. Use a sealant to waterproof any drill holes.
    • For window placement, ensure the antenna is as close to the glass as possible, avoiding metal frames that might obstruct signal reception.
    • Route the antenna cable to the accelerograph, avoiding sharp bends. Use cable conduits if necessary to protect the cable from damage.
  • Cabling and Power Connection:
  • Connect the GPS antenna to the designated port on the accelerograph.
    • Ensure all cables are neatly routed and secured.
    • Connect the accelerograph to a power source, using a surge protector. Make sure that the power outlet is grounded.
  • Initial Setup:
  • Follow the manufacturer’s instructions to power on and configure the accelerograph.
    • Verify the GPS connection and perform any required calibrations.
  • Testing:
  • Conduct initial tests to ensure the accelerograph is recording data accurately.
    • Verify that the data can be retrieved and is consistent with expectations.

Post-Installation

  • Documentation: Keep a record of the installation details, including the location, date of installation, and any specific configurations.
  • Maintenance Schedule: Establish a regular maintenance schedule to inspect the accelerograph, its connections, and the surrounding area to ensure continued accuracy and performance.

Notes

  • Always refer to the manufacturer’s installation guidelines for specific instructions related to your accelerograph model.
  • Consider local building codes and regulations when installing external components.
  • For installations in areas with extreme weather conditions, additional protective measures may be required for the outdoor components.

By following these comprehensive instructions, you can ensure the successful installation of an accelerograph and its GPS antenna within a building, facilitating accurate seismic data collection and analysis.

Questions?

Email us at support@quakelogic.net or call us at +1-916-899-0391.

Key Takeaways

  • Install close to the building's structural core, away from heavy machinery and HVAC, preferably on the floor in a NEMA enclosure.
  • Keep at least 1 ft (about 0.3 m) of clearance around the unit for ventilation and access.
  • Wall or ceiling mounts use the central key-hole slot; bolt head 12 to 14 mm, bolt stem at least 8 mm, heavy-load dowel.
  • Above 1 m elevation a safety chain or steel cord is mandatory; check all retention devices every year.
  • GPS antenna needs a clear sky view for absolute timing; place it close to the window glass away from metal frames, seal outdoor drill holes.

Frequently Asked Questions

Where should an accelerograph be installed inside a building?

Install the accelerograph close to the building's structural core in a location that minimizes vibration from non-seismic sources such as heavy machinery and HVAC systems. Floor mounting inside a NEMA enclosure is preferred. Keep at least 1 ft (about 0.3 m) of clearance for ventilation and access, and choose a site reachable for maintenance, for example behind an access panel or removable ceiling tiles.

How do I mount an accelerograph on a wall or ceiling?

For wall or ceiling installation use the unit's central key-hole hooking slot with a heavy-load dowel suited to concrete or brick. The bolt head should be 12 mm (maximum 14 mm) to leave leveling freedom and the bolt stem at least 8 mm. For mounts above 1 m, attach a safety chain or steel cord to a threaded hole and inspect it yearly. Do not overtighten the feet, and keep the bonding tight so vibrations are measured correctly.

Where should the GPS antenna for an accelerograph be placed?

The GPS antenna provides absolute timing for waveform time-stamps, so it needs a clear view of the sky. Place it on or near a window sill as close to the glass as possible, away from metal frames, or mount it externally with no tall buildings or heavy foliage in the way. Seal any outdoor drill holes with sealant and route the cable to the accelerograph without sharp bends, using conduit where needed.

How are the leveling pads and floor bolt used on an accelerograph?

In a floor installation the accelerograph is fixed down by a bolt set in the concrete while the leveling pads are adjusted to push the sensor up against it, working in counteraction to level the unit. Counter-lock paddles are optional but good practice. A shaft or large steel baseplate can replace a dowel for added security. Avoid overtightening the feet, which can damage the case.

What should be done after installing an accelerograph?

After installation, power the accelerograph through a grounded outlet with a surge protector, follow the manufacturer's configuration steps, confirm the GPS connection and run any required calibration. Record test data and verify it can be retrieved and looks as expected. Document the location, date and configuration, and set a regular maintenance schedule to inspect the unit, its connections and the mounting.

Need help with a project? QuakeLogic designs and supplies seismic monitoring, earthquake early warning, structural health monitoring, infrasound, and shake table systems. Browse QuakeLogic products or contact our engineering team with your site, structure, or test requirements.

How to Process Infrasound Data: Baseline and Bandpass Steps

Infrasound sensor used to record low-frequency acoustic signals for processing and analysis

In short: Infrasound signal processing follows six steps: pre-process the raw record (digitize, time-sync, remove outliers); correct baseline drift by subtracting a constant, a polynomial fit or a moving average; bandpass-filter to the band of interest, below 20 Hz, with a Butterworth, Chebyshev or Bessel design; convert the filtered signal to Pascals using the sensor sensitivity; detrend, window and apply extra noise reduction; then measure event amplitude, frequency content, phase and duration.

Processing infrasound signals is a critical step in analyzing data from phenomena that generate low-frequency acoustic waves. These waves can originate from various sources, including natural events (volcanic eruptions, tornadoes, etc.), man-made explosions, and large machinery. The goal of post-processing infrasound data is to enhance signal quality, making it easier to detect and analyze these phenomena. Here’s a detailed explanation of the post-processing steps, including baseline correction and bandpass filtering:

1. Pre-Processing:

Before diving into specific post-processing techniques, it’s essential to ensure that the raw infrasound data is correctly pre-processed. This might include steps like digitization (if working with analog signals), ensuring correct time synchronization, and initial data cleaning to remove any obvious errors or outliers.

2. Baseline Correction:

Infrasound signals can be affected by drift and shifts in the baseline, which can obscure the true signal or make analysis more difficult. Baseline correction aims to adjust the signal so that its baseline is stable over time, which is crucial for accurate measurement and analysis.

  • Identify the Baseline: Using statistical methods or by visually inspecting the signal, determine the baseline level. This could be a constant value that the signal should nominally return to in the absence of any events.
  • Correction Methods: Apply a method to correct the baseline drift. This might involve subtracting the identified baseline value from the entire signal or using more sophisticated methods like polynomial fitting or moving average subtraction to adjust dynamically for baseline changes over time.

3. Bandpass Filtering:

Bandpass filtering is used to remove noise and irrelevant frequencies that do not contribute to the signal of interest. By focusing on a specific frequency band, it enhances the signal’s detectability and clarity.

  • Determine Frequency Band: Based on the source and nature of the infrasound signal, identify the relevant frequency range. Infrasound signals typically fall below 20 Hz, but the exact band of interest can vary depending on the source and environment.
  • Apply Filter: Use a bandpass filter to retain only the frequencies within the desired range. Common types of bandpass filters include Butterworth, Chebyshev, and Bessel filters, each with its characteristics in terms of phase shift and roll-off rate. The choice of filter depends on the analysis requirements and the characteristics of the signal.
  • Filter Design: The filter can be designed digitally in software, specifying the passband (the range of frequencies to keep), the stopband (frequencies to be attenuated), and the filter order (which affects the steepness of the roll-off). Higher-order filters provide sharper cutoffs but can introduce phase distortion.

4. Convert to Pascal Values:

After filtering, the signal is often converted into physical units (e.g., Pascals) for analysis. This step involves calibrating the signal based on the sensitivity of the infrasound sensors used to record the data and any known reference levels. Calibration ensures that the signal amplitude reflects the true pressure variations caused by the infrasound source.

For detailed information on this step, visit this link:

Converting Infrasound Sensor Data to Pascal: A Step-by-Step Guide

5. Additional Processing Steps:

Depending on the application, further processing steps might be necessary, such as:

  • Detrending: Removing linear trends from the data to focus on the signal fluctuations.
  • Windowing: Applying a window function to manage the signal’s start and end points, useful for Fourier analysis.
  • Noise Reduction: Implementing additional noise reduction techniques, such as spectral subtraction or signal enhancement algorithms, to improve signal quality.

6. Analysis:

After post-processing, the signal is ready for analysis, which could involve identifying specific events, measuring their characteristics (amplitude, frequency content, phase, duration), and interpreting their source and impact.

In summary, the post-processing of infrasound raw signals, including baseline correction and bandpass filtering, is essential for accurately interpreting the data. These steps help in enhancing the signal quality by eliminating noise and irrelevant information, thereby facilitating a more precise analysis of the infrasound phenomena captured by the sensors.

Questions?

Email us at support@quakelogic.net or call us at +1-916-899-0391.

Key Takeaways

  • Infrasound signals fall below 20 Hz; the exact passband depends on the source (volcano, tornado, explosion, machinery).
  • Baseline correction options: constant subtraction, polynomial fitting or moving-average subtraction.
  • Butterworth, Chebyshev and Bessel bandpass filters differ in phase shift and roll-off; higher order sharpens cutoff but adds phase distortion.
  • Convert to Pascals after filtering using sensor sensitivity and known reference levels.
  • Optional steps: detrending, windowing for Fourier analysis, and spectral subtraction for noise reduction.

Frequently Asked Questions

What frequency band is used for infrasound signal processing?

Infrasound lies below 20 Hz, the lower limit of human hearing, so processing typically keeps a passband somewhere under that limit. The exact band depends on the source: volcanic eruptions, tornadoes, explosions and large machinery each concentrate energy in different parts of the infrasound range, and local environmental noise also shapes the choice. The passband, stopband and filter order are then specified when the bandpass filter is designed.

How do you correct baseline drift in infrasound data?

First identify the baseline, the level the signal should return to with no events, either statistically or by visual inspection. Then remove the drift: subtract a constant baseline value from the whole record for simple offsets, or use polynomial fitting or moving-average subtraction when the baseline wanders over time. A stable baseline is needed before filtering and conversion to Pascals so that amplitudes are measured correctly.

Which bandpass filter is best for infrasound: Butterworth, Chebyshev or Bessel?

Each filter trades off differently. Butterworth gives a flat passband with moderate roll-off; Chebyshev gives a steeper roll-off at the cost of passband ripple; Bessel preserves phase and waveform shape best but rolls off most gently. Higher filter orders sharpen the cutoff but introduce more phase distortion. Choose by what the analysis needs: waveform timing favors Bessel, sharp band separation favors Chebyshev, general use favors Butterworth.

Why convert infrasound data to Pascals?

Raw infrasound records are in sensor output units, such as volts or digitizer counts. Converting to Pascals calibrates the signal using the sensor's sensitivity and any known reference levels so that amplitude represents the true pressure variation produced by the source. Physical units make results comparable across sensors and sites and let analysts quantify event strength. QuakeLogic's separate guide on converting infrasound sensor data to Pascal details the calculation.

What are the steps to process raw infrasound data?

Six steps: pre-processing (digitization if analog, time synchronization, removal of obvious errors and outliers); baseline correction to remove drift; bandpass filtering to retain the frequency band of interest; conversion to Pascals using sensor sensitivity; optional detrending, windowing for Fourier analysis and noise reduction such as spectral subtraction; and finally analysis, where events are identified and their amplitude, frequency content, phase and duration are measured and interpreted.

Need help with a project? QuakeLogic designs and supplies seismic monitoring, earthquake early warning, structural health monitoring, infrasound, and shake table systems. Browse QuakeLogic products or contact our engineering team with your site, structure, or test requirements.

🚨🌍 On-site Earthquake Early Warning: A Must-Have for Urban Zones Like San Francisco Bay & Downtown LA, Istanbul 🌍🚨

Seismic monitoring instrumentation for "🚨🌍 On-site Earthquake Early Warning: A Must-Have for Urban Zones Like San Francisco Bay

In the heart of our bustling cities, lying within just 15 miles of urban settings, fault lines silently weave. Areas like the San Francisco Bay Area, Downtown Los Angeles and Istanbul sit precariously close to these seismic threats, making them vulnerable to the devastating impacts of earthquakes without a moment’s notice.

Traditional network-based earthquake early warning systems face a critical challenge in these ‘blind zones.’ The proximity to fault lines significantly reduces the time available to relay warnings, leaving little to no margin for preventative action. This is where QuakeLogic’s On-Site Earthquake Early Warning System becomes not just a necessity but a life-saving innovation.

Seismic monitoring instrumentation for "🚨🌍 On-site Earthquake Early Warning: A Must-Have for Urban Zones Like San Francisco Bay

Our cutting-edge technology offers a solution that ensures businesses, factories, and public spaces can automatically:

  • Shut down critical equipment to prevent damage
  • Alert individuals to ‘Drop, Cover, and Hold On’ for personal safety
  • Open gates to facilitate emergency exits and rescue operations

By implementing QuakeLogic’s on-site system, you’re not just safeguarding your infrastructure and assets but, more importantly, the lives of those within your premises. Additionally, aligning with insurance requirements becomes streamlined, saving lives and minimizing downtime, ultimately leading to cost savings.

QUAKEALERT for "🚨🌍 On-site Earthquake Early Warning: A Must-Have for Urban Zones Like San Francisco Bay & Downtown

Don’t wait for the ground to shake to recognize the need for advanced preparations. Contact us at sales@quakelogic.net or visit our website https://www.quakelogic.net/earthquake-early-warning-products to learn more about how QuakeLogic can fortify your readiness against earthquakes.

🛡️ Together, let’s make safety a priority and ensure that when nature strikes, we’re prepared, not scared.

#EarthquakePreparedness #SafetyFirst #QuakeLogic #EarthquakeEarlyWarning #SanFrancisco #LosAngeles #ProtectYourBusiness

Last reviewed: 2026-07-04

Executive Summary

Earthquake early warning combines rapid detection, local or regional algorithms, alert logic, and response procedures before strong shaking reaches a site. This article has been expanded as an engineering resource for readers evaluating earthquake early warning concepts, instrumentation choices, and monitoring workflows. The discussion is educational and should be paired with project-specific review by qualified engineers, applicable codes, owner requirements, and equipment documentation.

Key Takeaways

  • Define the engineering objective before selecting sensors, test equipment, trigger thresholds, or reporting workflows.
  • Use calibrated instrumentation, documented installation practices, time synchronization, and traceable data handling where measurement quality matters.
  • Interpret measured data in context: site conditions, structure type, noise environment, sampling rate, bandwidth, and boundary conditions all affect conclusions.
  • Use authoritative references and project-specific criteria rather than relying on generic thresholds or unsupported performance claims.

Technical Explanation

In practical earthquake early warning work, the engineering system is more than a sensor or a test platform. A credible workflow includes the measurement objective, instrument selection, mounting or boundary conditions, sampling and timing strategy, data validation, event or response detection, engineering review, and reporting. Weakness in any part of that chain can reduce confidence in the final interpretation.

For monitoring applications, engineers should document sensor orientation, coupling, environmental exposure, dynamic range, frequency bandwidth, data logger configuration, clock synchronization, communications, and maintenance procedures. For testing applications, engineers should document input motion, fixture design, payload properties, control limits, safety interlocks, acceptance criteria, and post-test data review.

Engineering Applications

ApplicationEngineering QuestionTypical Evidence Needed
Research and educationHow does a structure, component, or sensor respond under controlled conditions?Test plan, calibrated data, input motion, boundary conditions, and repeatable observations.
Critical infrastructureIs the asset response normal, changing, or potentially unsafe after an event?Baseline data, event records, thresholds, inspection workflow, and engineering sign-off.
Industrial facilitiesCan monitoring support operational continuity and response decisions?Site-specific criteria, reliable telemetry, alarm logic, maintenance records, and documented procedures.

People Also Ask

What should be specified before buying equipment?

Specify the measurement objective, frequency range, amplitude range, environment, data format, timing needs, installation constraints, reporting requirements, and applicable standards or owner criteria.

Why do references and standards matter?

They provide terminology, acceptance criteria, test methods, and documentation expectations. They do not replace engineering judgment, but they reduce ambiguity and make results easier to review.

How should data quality be checked?

Review calibration status, timing, clipping, sensor orientation, signal-to-noise ratio, environmental artifacts, data completeness, and whether the record supports the engineering decision being made.

Related QuakeLogic Resources

References

Recommended Diagram or Download

Media placeholder: Add an original diagram showing the measurement chain from sensor or test platform to data acquisition, analysis, engineering interpretation, and reporting. Where this article becomes a buyer guide or application note, create a downloadable PDF version after engineering review.

Discuss a Monitoring or Testing Application

QuakeLogic supports seismic monitoring, earthquake early warning, structural health monitoring, infrasound monitoring, vibration monitoring, data acquisition, and shake table testing applications. For project-specific guidance, contact QuakeLogic with the asset type, measurement objective, site constraints, and required deliverables.