Joint observation of long period tremor signals with broadband seismometer, tiltmeter and gravimeter

Zhang, Yanbin; Jiang, Jun; Liao, Ying-chun; Li, Shengle; Zhong, Tie-tao

doi:10.1007/s11589-008-0629-y

Cited by 4 publications

(5 citation statements)

References 11 publications

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“…As such, the pre-seismic anomaly would be significant noise for interpreting the gravity changes a few hours before the M w 9.0 Tohuku-oki earthquake. In fact, the pre-seismic anomalies have been reported using different types of instruments including seismometer, tiltmeter and gravimeter as well (Hao and Hu 2008;Zhang et al 2008;Hu et al 2010;Shen et al 2011). However, the dominant frequencies of pre-seismic anomalies are higher than 0.10 Hz, and the frequency of seismic-related signals is below 0.10 Hz which is as same as in this study.…”

Section: Discussionsupporting

confidence: 79%

Superconducting Gravimeters Detect Gravity Fluctuations Induced by Mw 5.7 Earthquake Along South Pacific Rise Few Hours Before the 2011 Mw 9.0 Tohoku-Oki Earthquake

Zhang¹,

Ma²

2014

Terr. Atmos. Ocean. Sci.

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Gravity changes sometimes appear before a big earthquake. To determine the possible sources is important for recognizing the mechanism and further geodynamic studies. During the first two hours on March 11 before the M w 9.0 Tohoku-Oki earthquake, the non-tidal gravity time series of superconducting gravimeters worldwide showed low-frequency (< 0.10 Hz) fluctuations with amplitude of ~1 to 4 × 10 -8 ms -2 lasting ~10 -20 minutes. Through comparing global seismicity with the arrival times of seismic waves, we find that the fluctuations were induced by the M w 5.7 earthquake that occurred at 0:14:54.68 at (53.27°S, 118.18°W) along the eastern South Pacific Rise. Several body waves such as P, S are clearly recorded in the station with ~400 km distance to the hypocenter. The fluctuations are in response to the waves that propagate with a velocity of about 4 km s -1 . Their amplitudes are proportional to the inverse of the epicentral distances even though the fluctuations of European sites were overlapped with waves associated with a smaller, i.e., M w 2.6, event in Europe during this period. That is, the M w 5.7 earthquake induced remarkable gravity fluctuations over long distances at stations all over the world. As such, the foreshocks with larger magnitudes occurred before the M w 9.0 earthquake would have more significant influence on the gravity recordings and the seismic-wave induced component should be removed during the analysis of anomalies prior to a great earthquake in future studies.

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Section: Discussionsupporting

confidence: 79%

Superconducting Gravimeters Detect Gravity Fluctuations Induced by Mw 5.7 Earthquake Along South Pacific Rise Few Hours Before the 2011 Mw 9.0 Tohoku-Oki Earthquake

Zhang¹,

Ma²

2014

Terr. Atmos. Ocean. Sci.

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“…In addition, the response the 2 channel to the tide are largely consistent, while that to seismic waves are obviously different. In fact, since the observation at the station began, DZW gravimeter and VS-1 tiltmeter have recorded some "spindle-like" anomalous tremor waves of consistent form by the output from channel LP1, which is common and frequent [1] . They have the same duration and morphology with the observation of broadband seismometer and can verify each other.…”

Section: Outline Of Background and Observations Of Hust Stationmentioning

confidence: 99%

“…In the observations of the earth tide, we often find out some anomalous microseisms in the tidal signals [1] . Compare with earth tide, the anomalous microseism is a high-frequency signal, with periods from a few seconds to a day.…”

Section: Introductionmentioning

confidence: 98%

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Anomalous Tremor Waves in Tidal Observations

Jiang

Zhang

Lin

et al. 2013

Chinese J of Geophysics

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In observations of the earth tide, there are often some anomalous microseisms in tidal signals. These microseisms are observed by broadband digital seismographs at the same time. Some of these microseisms are generated by tropical cyclones in the western Pacific, and others are mostly accompanied by major earthquakes, called anomalous tremor waves. This article outlines the earthquake and tide observation station of the Huazhong University of Science and Technology (HUST), and reports the anomalous tremor waves recorded by the DZW gravimeter and VS‐1 tiltmeter at this station. A lot of observations show that the anomalous tremor waves appeared in the records of the low‐pass 1 channel (LP1) of the DZW gravimeter and VS‐1 tiltmeter, but were rare in that of the low‐pass 2 channel (LP2) of the instruments and other tidal instruments. The envelope of the anomalous tremor waves is mostly like a spindle or tail, with a duration of 1 to 3 days. The research of the anomalous tremor waves and the tidal instruments suggests that these anomalous tremor waves are actually micro‐tremor signals originated from complex sources, which have a wide response range, and can be recorded by broadband digital seismographs and tidal instruments. The main periods of the anomalous tremor waves aroused by the tropical cyclone in the western Pacific are about 3∼7 s, and the tremor waves before earthquakes have not only a main period of 3∼7 s but also 10∼60 s or longer periods. The differences of the responses of tidal instruments to anomalous tremor waves are mainly decided by the transfer function and property of the instruments. The DZW gravimeter and VS‐1 tiltmeter take samples per minute, so the anomalous tremor waves are the aliasing or mapping of the real signals. Whether the anomalous tremor waves before earthquakes are related to the earthquakes, or a seismic precursor needs more detailed and deeper analysis.

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“…Therefore, the observation and understanding of the tremor are still accumulating. In these several years, we have researched low-frequency micro-vibration and long sequence of signals observed by broadband seismometer, tiltmeter and gravimeter in China mainland, and found a lot of new and unknown signals with diverse characters [6,7] . Some of the tremors are caused by tropical cyclones.…”

Section: Introductionmentioning

confidence: 99%

The Tropic Cyclone Aroused the Tremor

Zhang

Jiang

et al. 2010

Chinese J of Geophysics

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This paper reports the tremor triggered by the tropic cyclone. The character of tremor signal is that the envelope like a spindle overlaps with the observational background curve, with a duration of 2 to 3 days, and the tremor frequency domain in the range of 0.13 to 0.33 Hz (period 3 s to 7 s). Most of the broadband seismometer, tiltmeter and gravimeter in China mainland can record the tremor. We study the cross‐correlation between the cyclone and tremor. The result shows that the intensity, moving path of the cyclone and the distances between the cyclone and stations have strong cross‐correlation with tremor. Based on this result, we conclude that this tremor is caused by the friction and the interaction between cyclone and the continental shelf, the surface of the earth and ocean, and the fault of plate responding to cyclone. Besides we study the cyclone generated in Bay of Bengal in North Indian Ocean and landed in Myanmar. The result shows that comparing to the cyclone in Western Pacific ocean, the cyclone generated in North Indian Ocean has little effect on tremor observed in China mainland.

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Joint observation of long period tremor signals with broadband seismometer, tiltmeter and gravimeter

Cited by 4 publications

References 11 publications

Superconducting Gravimeters Detect Gravity Fluctuations Induced by Mw 5.7 Earthquake Along South Pacific Rise Few Hours Before the 2011 Mw 9.0 Tohoku-Oki Earthquake

Superconducting Gravimeters Detect Gravity Fluctuations Induced by Mw 5.7 Earthquake Along South Pacific Rise Few Hours Before the 2011 Mw 9.0 Tohoku-Oki Earthquake

Anomalous Tremor Waves in Tidal Observations

The Tropic Cyclone Aroused the Tremor

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