Theoretical Frequency Response and Corresponding Bandwidth of an Empty Borehole for The Measurement of Strain Waves in Borehole Tensor Strainmeters

Zhang, Kanghua; Tian, Jiayong; Hu, Zhifei

doi:10.1785/0120180264

Cited by 5 publications

(2 citation statements)

References 28 publications

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“…For the different gauge arrangements in RZB-type and YRY-type BTSMs, three frequency response 4 FV , 2 FV , and TV reflecting areal strain and two frequency response functions FS and TS reflecting shear strain of incident wave have been presented [6]. In this paper, other two frequency response functions are introduced based on the three other gauge-response combinations…”

Section: Instrumental Responses Of Btsm Based On Scattering Model Of ...mentioning

confidence: 99%

Instrumental response of borehole tensor strainmeters for oblique-incident seismic waves

Tian¹,

Zhang

Lou³

2023

IOP Conf. Ser.: Earth Environ. Sci.

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It has been proven qualitatively that borehole tensor strainmeters (BTSM) could measure three surface-wave-induced strain components in the horizontal-normal plane. But strain waves are usually incident obliquely to borehole axis to induce not only horizontalnormal strain components but also the three other strain components in the plane of vertical normal, which are usually assumed to zero in conventional model of BTSM installed near the earth surface. Therefore quantitative kinematical-parameter measurement of strain waves of wave normal oblique to borehole axis by BTSM is still a challenging problem. In this paper, a scattering model of oblique-incidence seismic waves by an empty borehole is introduced to investigate instrumental responses of BTSM. Besides for the four gauges in conventional BTSM, three other gauges considering the influences of strain components in the plane of vertical normal are also introduced to build dynamic calibration matrix between instrumental and incident strains. It shows that within the effective bandwidth of BTSM, zero-frequency-gain for dynamic calibration matrix could be adopted approximately to build quantitative relation between instrumental strain waves of BTSM and oblique-incidence seismic strain waves. It is shown that the recommended gauge combinations could promise quantitative measurement of kinematic parameters of the incident strain P or S wave if high-resolution insitu calibration of BTSM has been conducted, which is important to the development of early warning system by borehole strainmeters.

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Section: Instrumental Responses Of Btsm Based On Scattering Model Of ...mentioning

confidence: 99%

Instrumental response of borehole tensor strainmeters for oblique-incident seismic waves

Tian¹,

Zhang

Lou³

2023

IOP Conf. Ser.: Earth Environ. Sci.

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“…YRY-4-type FGBS has good observation performance and has achieved great success in the study of geodynamic problems (Chi et al, 2009;Qiu et al, 2013;Liu et al, 2014). Some scholars have also studied the theoretical issues and feasibility of using the observed seismic strain waves (Zhang et al, 2019;Zhang et al, 2020;Zhang et al, 2021), but there has been no actual observation to verify the results. For the two earthquakes, the P and S waves of seismic strain waves recorded by the YRY-4-type FGBS at all the sites are apparent in Figure 4.…”

Section: Datamentioning

confidence: 99%

The apparent focal depth, emergence angle, and take-off angle of seismic wave measured by YRY-4-type borehole strainmeter as one kind of strain seismograph

Tang

Qiu²,

Fan

et al. 2023

Front. Earth Sci.

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Introduction: In theory, the observation objects and principles of strain seismograph and traditional pendulum seismograph are different, and the characteristics of observed signals should also be dissimilar. The observation results of pendulum seismograph show that seismic waves in inhomogeneous media will undergo refraction, reflection, and attenuation. Then, what signal characteristics can be detected by strain seismograph is great significance for understanding and explaining the observation results.Methods: Using YRY-4 type four-gauge borehole strainmeter as one kind of strain seismograph to detect the strain tensor change of the plane seismic wave emitted from the surface, a five-site strain seismograph observation network was built in Shanxi Province, with continuous observation for 2 years at a sampling rate of 100 Hz. In this paper, two local events occurring in the area covered by the strain seismograph observation network are taken as examples. We systematically studied the characteristics of seismic wave signals recorded by strain seismographs at five sites, inverted for the focal depth of the two local earthquakes and the relationship between the wave velocity and the wave velocity gradient of the focal depth, and calculated the apparent focal depth, the emergence angle and the take-off angle of seismic waves.Results: These results show stable uniqueness and apparent regularity, especially since the inverted focal depths are basically consistent with the seismic solutions based on those traditional pendulum seismographs. The observations from this study show that the strain seismograph can be used as an effective supplement to the pendulum seismograph.Discussion: In the future, we will continue to study the rupture process and focal mechanism of moderate-strong earthquakes and teleseismic earthquakes by combining two kinds of observations.

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The Potential of Using Dynamic Strains in Earthquake Early Warning Applications

Farghal

Barbour

Langbein

2020

Seismological Research Letters

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Abstract We investigate the potential of using borehole strainmeter data from the Network of the Americas (NOTA) and the U.S. Geological Survey networks to estimate earthquake moment magnitudes for earthquake early warning (EEW) applications. We derive an empirical equation relating peak dynamic strain, earthquake moment magnitude, and hypocentral distance, and investigate the effects of different types of instrument calibration on model misfit. We find that raw (uncalibrated) strains fit the model as accurately as calibrated strains. We test the model by estimating moment magnitudes of the largest two earthquakes in the July 2019 Ridgecrest earthquake sequence—the M 6.4 foreshock and the M 7.1 mainshock—using two strainmeters located within ∼50 km of the rupture. In both the cases, the magnitude based on the dynamic strain component is within ∼0.1–0.4 magnitude units of the catalog moment magnitude. We then compare the temporal evolution of our strain-derived magnitudes for the largest two Ridgecrest events to the real-time performance of the ShakeAlert EEW System (SAS). The final magnitudes from NOTA borehole strainmeters are close to SAS real-time estimates for the M 6.4 foreshock, and significantly more accurate for the M 7.1 mainshock.

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Theoretical Frequency Response and Corresponding Bandwidth of an Empty Borehole for The Measurement of Strain Waves in Borehole Tensor Strainmeters

Cited by 5 publications

References 28 publications

Instrumental response of borehole tensor strainmeters for oblique-incident seismic waves

Instrumental response of borehole tensor strainmeters for oblique-incident seismic waves

The apparent focal depth, emergence angle, and take-off angle of seismic wave measured by YRY-4-type borehole strainmeter as one kind of strain seismograph

The Potential of Using Dynamic Strains in Earthquake Early Warning Applications

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