China
Africa
Explore chapters and articles related to this topic
Sensors and sensory systems
Published in You-Lin Xu, Jia He, Smart Civil Structures, 2017
Seismometers are instruments that measure motions of the ground, including those of seismic waves generated by earthquakes, nuclear explosions and other sources. As ground motion causes its frame to move, a fixed reference point is required for a seismometer taking measurements. Hence, the installation of a mechanical oscillator can be in the form of a mass-spring system (mobile mass attached to the frame by a spring) or a horizontal pendulum (mobile mass offset from the vertical axis of rotation). Accordingly, there is one way to classify the seismic sensors based on the measurement direction and the aforementioned properties of a mechanical oscillator: either vertical or horizontal. A vertical seismometer, which is used to measure vertical ground motion, utilises an oscillator based on the mass-spring system to compensate for gravity. A horizontal seismometer, which is used to measure horizontal ground motion, is based on the horizontal pendulum principle.
Test-Ban Treaty Verification and the Role of Seismology: UK Efforts 1958–1965
Published in John R. Walker, British Nuclear Weapons and the Test Ban 1954–1973, 2016
One of the major problems was provision of suitable seismometers that could reduce the signal to noise ratio. UKAEA experts considered three projects to address this problem. The first of these would look at the possibility of increasing the number of seismometers at a seismic station and deploying them in some form of array; the second would place seismometers down deep boreholes, the third was to conduct some borehole experiments to discover the optimum depth at which to place seismometers.37 The AWRE Weapons Group undertook this work. This resulted in work done out at depths of 300 and 500 feet in boreholes made available by BP and the University of Durham; and thirdly AWRE would seek sites where the noise levels were much better than those used in the various systems studied so far. As part of this work, the UKAEA established a small array at Porton Down on Salisbury Plain to act as the prototype of the Eskdalemuir array.38
Vibration Instruments and Measurement Steps
Published in Jyoti K. Sinha, Industrial Approaches in Vibration-Based Condition Monitoring, 2020
Seismometer is a sensor to measure the vibration velocity and commonly used to measure the seismic events. It is generally bulky and hence not commonly used to measure machine vibration now-a-days. Hence this sensor is not discussed here but refers Sinha (2015) for further details.
Source parameters and scaling relations for small earthquakes in mainland Gujarat region of Western Deccan Volcanic Province, India
Published in Geomatics, Natural Hazards and Risk, 2022
As part of this study, digital data were acquired from eight permanent broad-band seismic stations of Gujarat (India) State Seismic Network (GSNet) (Chopra et al. 2008; Kumar et al. 2012). Granite and basalt are the most common lithographic foundations for these stations (Shastri and Kumar 2021). All the stations have 120 s broadband sensors of Nanometrics and Guralp make and 24-bit digitizers. The BBS are running on continuous mode and are recording the data at 50 samples/s and with GPS time synchronization. The instrument response of the recording equipment is almost flat to ground velocity between the natural frequency of the seismometer used, i.e. 0.0083–50 Hz. Our data set consists of 43 earthquakes of magnitude ranging from 2.5 to 4.3. A good Signal-to-noise ratio (i.e. S/N ≥ 3) and well located earthquakes were considered while selecting the earthquakes. The hypo-central distances of the recording stations vary between 10 and 250 km, whereas the focal depth falls in the range of 2–33.7 km. The earthquakes investigated have been recorded at four or more stations. The epi-central parameters are shown in Table 1. Figure 1 shows the earthquake locations of events used in the present study and recording stations. In MG, earthquake spatial distributions correlate well with main active faults (Figure 1). The events used here are mainly shallow, being located at the depths ≤40 km, thus mostly above the Moho (assumed 30 km). Figure 2 is the recorded seismogram of Surat earthquake that occurred on 17 July 2016.
Using a dense seismic array to study fluvial processes in a braided river reach under flood conditions
Published in LHB, 2022
Marco Piantini, Florent Gimbert, Maarten Bakker, Alain Recking, Ugo Nanni
The seismometers record ground motions at a sampling frequency of 250 Hz, allowing the assessment of seismic waves up to 125 Hz. However, we apply a 5–20 Hz band-pass filter to the data in order to focus on turbulence and bedload-induced ground motions (Bakker et al., 2020), thus removing all non-fluvial sources (e.g. rainfall-induced high-frequency ground vibrations (Roth et al., 2016)).