CASE STUDIES
UPDATE
January 11, 2024
Short-period Seismic Nodes: A new revolution in seismological research
Short-period seismometers, known for their portability, cost-effectiveness, and efficiency, enable the possibility of large-scale, ultra-dense array studies.

Currently, dense array observations have emerged as a crucial tool in seismic research. Using short-period nodal seismometers for regional dense array observations allows for more precise acquisition of regional earthquake catalogs and a finer characterization of subsurface velocity structures. Short-period seismometers, known for their portability, cost-effectiveness, and efficiency, enable the possibility of large-scale, ultra-dense array studies.


In order to gain a deeper understanding of the signal response performance of short-period nodal seismometers, a research team from China University of Geosciences (Wuhan) recently conducted a comparative experimental study on instrument performance. Four SmartSolo IGU-16HR 3C short-period Seismic nodes were deployed at four observation points within the Hubei Seismic Network compared with the National Broadband Seismometer.

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Experiment

➣Station Deployment:

Four observation points with national broadband seismometers in Hubei Province


Observation:

➣Duration:2022.2-2023.5

➣Sample Rate:100Hz

➣Instruments:National Broadband Seismometer、IGU-16HR3C 5Hz


Methods:

➣Comparison of Far-field P-wave absolute amplitudes

➣Comparison of P-wave receiver function amplitudes

➣Comparison of P-wave polarization values

➣Comparison of Ambient noise cross-correlation functions and Phase velocity dispersion curves

                                                                  

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Through three months observation, the research team acquired a substantial volume of seismic data and arrived at the following research findings.


Far-field P-wave absolute amplitudes

                                                                 

Filter: 2-3Hz、1-3Hz、1-2Hz、0.5-1Hz、0.1-0.5Hz


Station and Events distribution


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Comparison of far-field P-wave absolute amplitudes across different frequency bands National Broadband Seismometer (Red) vs. IGU-16HR3C 5Hz (Blue)

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The far-field absolute amplitude of P-waves recorded by the IGU-16HR3C 5Hz maintaining good consistency with the National Broadband Seismometer even at a corner frequency of 0.1Hz. The time offset between the two instruments was within 0.02 seconds.


P-wave receiver function


Parameter:

➣Filter:0.05-3Hz

➣Window:-10s – 80s

➣Gaussian filter factor:5(2.4Hz)


QC:

➣Cross-correlation factor:0.6

➣Window:-10s – 100s


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Quality control of cross-correlation for XNI station receiver functions Receiver function (Black); Stacked averaged receiver function (Red)


Comparison of P-wave receiver functions 

National Broadband Seismometer (Red) vs. IGU-16HR3C 5Hz (Blue)


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The standard deviation of P-wave receiver functions from two instruments


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The far-field P-wave receiver functions extracted from the IGU-16HR3C 5Hz maintaining good consistency with the National Broadband Seismometer within the frequency range of 0.05 to 3Hz. The Amplitudes and Phases exhibit substantial similarity, with a standard deviation of less than 2% between the two devices.


P-wave polarization


Parameter

➣Filter:0.05-3Hz

➣Window:-10s – 80s

➣Polarization calculation period :0s - 6s

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Figures a - c: The apparent S-wave velocity variations for all events recorded by the National Broadband Seismometer;


Figures d - f: The apparent S-wave velocity variations after stacking averaging by the National Broadband Seismometer;


Figures g - i: The apparent S-wave velocity variations for all events recorded by the IGU-16HR3C 5Hz;


Figures j - l: The apparent S-wave velocity variations after stacking averaging by the IGU-16HR3C 5Hz.


Comparison of apparent S-wave velocity variation curves

National Broadband Seismometer (Red) vs. IGU-16HR3C 5Hz (Blue)

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The standard deviation of S-wave velocity variation from two instruments


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The apparent S-wave velocity curve from the IGU-16HR3C 5Hz remains consistent with the National Broadband Seismometer within the 0s-6s frequency range. The difference between the two instruments does not exceed 0.1 km/s, with a standard deviation of within 6%.


Ambient noise

cross-correlation functions


Cross-correlation functions of ambient noise data for six station pairs

National Broadband Seismometer (Red) vs. IGU-16HR3C 5Hz (Blue)

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The Ambient noise cross-correlation functions computed by the IGU-16HR3C 5Hz exhibit good consistency with the National Broadband Seismometer within the 0.1-0.5Hz range.


Phase velocity dispersion curves 

National Broadband Seismometer and IGU-16HR3C 5Hz (Scatter plots)

Reference phase velocity curve for the region (Blue)


National Broadband Seismometer and IGU-16HR3C 5Hz (Scatter plots)

Reference phase velocity curve for the region (Blue)


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The phase velocity dispersion curves extracted within 20 seconds by the IGU-16HR3C 5Hz demonstrate a good consistency with those obtained from the National Broadband Seismometer.


Conclusion


➣The far-field absolute amplitude of P-waves recorded by the IGU-16HR3C 5Hz maintaining good consistency with the National Broadband Seismometer even at a corner frequency of 0.1Hz. The time offset between the two instruments was within 0.02 seconds.


➣The far-field P-wave receiver functions extracted from the IGU-16HR3C 5Hz maintaining good consistency with the National Broadband Seismometer within the frequency range of 0.05 to 3Hz. The Amplitudes and Phases exhibit substantial similarity, with a standard deviation of less than 2% between the two devices.


➣The apparent S-wave velocity curve from the IGU-16HR3C 5Hz remains consistency with the National Broadband Seismometer within the 0s-6s frequency range. The difference between the two instruments does not exceed 0.1 km/s, with a standard deviation of within 6%.


➣The background noise cross-correlation functions computed by the IGU-16HR3C 5Hz instrument exhibit good consistency with the National Broadband Seismometer within the 0.1-0.5Hz range. Moreover, the extracted phase velocity dispersion curves within 20 seconds also demonstrate a consistent pattern between the two.


Positioned as an economical, streamlined, and efficient seismic observation tool, the short-period nodal seismometer demonstrates vast potential for broad application in seismic research and earthquake forecasting. With continual advancements in research methodologies and analytical techniques, we are confident that the short-period nodal seismometer will assume a crucial role in the future of seismology, driving significant breakthroughs in the field.