Normal Earthquake Gravitational Precursors from Earth-Tide Data

1982 ◽  
pp. 269-277
Author(s):  
E. Druta
Keyword(s):  
Earth Tide

scholarly journals Water level collapse effect of deep well in mining area

2021 ◽  
Vol 233 ◽  
pp. 03037
Author(s):  
LIN Mei ◽  
DONG Xiaona
Keyword(s):  
Water Level ◽  
Coal Mine ◽  
Earth Tide ◽  
Mining Area ◽  
Observation Data ◽  
Aquifer System ◽  
Deep Well ◽  
Original Curve ◽  
Level Data ◽  
Water Level Data

The use of Zaozhuang of Shandong province coal mine area is tao chong lu 15 Well and meteorological observation data, the three elements of observation Wells with tao chong effect comparing the dynamic characteristics of the mines. It is difficult to determine whether the stress state of the aquifer system in which the well was observed before the collapse has changed because of the water level in the deep well of Lu15 well on the original curve. Nakai fitting model is adopted to calculate the earth tide response amplitude factor ratio based on the water level data of Lu15 well, and the possibility of collapse caused by stress change is discussed in combination with non-natural seismic events in Taozhuang Coal mine

scholarly journals Evaluation of global ocean tide models based on tidal gravity observations in China

2020 ◽  
Author(s):  
Hongbo Tan ◽  
Chongyong Shen ◽  
Guiju Wu
Keyword(s):  
High Precision ◽  
Earth Tide ◽  
Global Ocean ◽  
Ocean Tide ◽  
Ocean Tides ◽  
Ocean Tide Model ◽  
Tidal Forces ◽  
The Earth ◽  
Gravity Observation ◽  
Ocean Tide Models

<p>Solid Earth is affected by tidal cycles triggered by the gravity attraction of the celestial bodies. However, about 70% the Earth is covered with seawater which is also affected by the tidal forces. In the coastal areas, the ocean tide loading (OTL) can reach up to 10% of the earth tide, 90% for tilt, and 25% for strain (Farrell, 1972). Since 2007, a high-precision continuous gravity observation network in China has been established with 78 stations. The long-term high-precision tidal data of the network can be used to validate, verifying and even improve the ocean tide model (OTM).</p><p>In this paper, tidal parameters of each station were extracted using the harmonic analysis method after a careful editing of the data. 8 OTMs were used for calculating the OTL. The results show that the Root-Mean-Square of the tidal residuals (M<sub>0</sub>) vary between 0.078-1.77 μgal, and the average errors as function of the distance from the sea for near(0-60km), middle(60-1000km) and far(>1000km) stations are 0.76, 0.30 and 0.21 μgal. The total final gravity residuals (Tx) of the 8 major constituents (M<sub>2</sub>, S<sub>2</sub>, N<sub>2</sub>, K<sub>2</sub>, K<sub>1</sub>, O<sub>1</sub>, P<sub>1</sub>, Q<sub>1</sub>) for the best OTM has amplitude ranging from 0.14 to 3.45 μgal. The average efficiency for O<sub>1</sub> is 77.0%, while 73.1%, 59.6% and 62.6% for K<sub>1</sub>, M<sub>2</sub> and Tx. FES2014b provides the best corrections for O<sub>1</sub> at 12 stations, while SCHW provides the best for K<sub>1 </sub><sub>,</sub>M<sub>2</sub>and Tx at 12,8and 9 stations. For the 11 costal stations, there is not an obvious best OTM. The models of DTU10, EOT11a and TPXO8 look a litter better than FES2014b, HAMTIDE and SCHW. For the 17 middle distance stations, SCHW is the best OTM obviously. For the 7 far distance stations, FES2014b and SCHW model are the best models. But the correction efficiency is worse than the near and middle stations’.</p><p>The outcome is mixed: none of the recent OTMs performs the best for all tidal waves at all stations. Surprisingly, the Schwiderski’s model although is 40 years old with a coarse resolution of 1° x 1° is performing relative well with respect to the more recent OTM. Similar results are obtained in Southeast Asia (Francis and van Dam, 2014). It could be due to systematic errors in the surroundings seas affecting all the ocean tides models. It's difficult to detect, but invert the gravity attraction and loading effect to map the ocean tides in the vicinity of China would be one way.</p>

Using earth-tide induced water pressure changes to measure in situ permeability: A comparison with long-term pumping tests

2016 ◽  
Vol 52 (4) ◽  
pp. 3113-3126 ◽  
Author(s):  
Vincent Allègre ◽  
Emily E. Brodsky ◽  
Lian Xue ◽  
Stephanie M. Nale ◽  
Beth L. Parker ◽  
...  
Keyword(s):  
Water Pressure ◽  
Earth Tide ◽  
Pumping Tests ◽  
In Situ Permeability ◽  
Pressure Changes

Earth-tide measurements with the superconducting gravimeter

1972 ◽  
Vol 77 (5) ◽  
pp. 926-937 ◽  
Author(s):  
W. A. Prothero ◽  
J. M. Goodkind
Keyword(s):  
Earth Tide ◽  
Superconducting Gravimeter

A high-sensitivity strain/inertial seismograph installation

1970 ◽  
Vol 60 (6) ◽  
pp. 1803-1822 ◽  
Author(s):  
James E. Fix ◽  
John R. Sherwin
Keyword(s):  
Environmental Control ◽  
Earth Tide ◽  
High Sensitivity ◽  
Low Noise ◽  
Photographic Film ◽  
Noise Levels ◽  
Directional Response ◽  
Long Period ◽  
Phase Velocities ◽  
Short Period

Abstract A seismograph complex consisting of short-period (SP), long-period (LP), and extended long-period (XLP) inertial and strain seismographs has been installed. Recordings are made on magnetic tape and photographic film. Routine magnifications on the 20-trace, 16-mm film recorders for all three components are: SP inertial, 500 K; LP inertial, 100 K. The noise levels permit equivalent magnifications on the strain seismographs. The complex provides seismic wave discrimination by directional response, which is independent of period, and by detection of differences in phase velocities between P, S, Love, or Rayleigh arrivals. The strain seismographs use 40-m-long rods and moving coil transducers with generator constants of 32,000 v/m/sec. They sense waves of 5 × 10-13 strain at 30 sec and reject the 2 × 10-8 earth-tide strain. A low-noise preamplifier drives a filter assembly which provides SP, LP, and XLP strain outputs. The complex is installed in an abandoned mine 50 km southeast of Phoenix, Arizona. Environmental control is provided by burial at a depth of about 110 m in a quartz diorite, by sealing the mine, and by insulating the seismometers.

Fundamental statistical techniques for the analysis of earth tides

1971 ◽  
Vol 61 (1) ◽  
pp. 203-215
Author(s):  
Cheh Pan
Keyword(s):  
Computer Technology ◽  
Earth Tide ◽  
Power Spectra ◽  
Correlation Coefficients ◽  
Earth Tides ◽  
Statistical Techniques ◽  
The Earth ◽  
Tidal Data ◽  
Instrumental Drift ◽  
Phase Differences

abstract Recent advances in instrumentation, digital computer technology and mathematical theory promote the error analysis of Earth-tide data. Various statistical techniques developed and used in other fields are applicable in the study of Earth tides, and the accuracy of the Earth's rigidity constants determined from the tides will be greatly improved with the help of these techniques. The fundamentals of the statistical techniques of autocorrelation, crosscorrelation, convolution, statistical means, bandpass filtering, correlation coefficients, power spectra, coherency and equalization are described, and their principal applications in the Earth-tide analysis summarized. Examples of effective application of these techniques in the elimination of the errors in the tidal data such as those introduced from instrumental drift, phase differences between the observed and predicted tides, etc. are discussed. This work is an attempt to introduce statistical analysis into the Earth-tide study.

Earthquake/earth tide correlation and other features of the Susanville, California, earthquake sequence of June-July 1976

1980 ◽  
Vol 70 (5) ◽  
pp. 1583-1593
Author(s):  
Amy S. Mohler
Keyword(s):  
Shear Stress ◽  
Compressive Stress ◽  
Sierra Nevada ◽  
Fault Plane ◽  
Earth Tide ◽  
P Wave ◽  
First Motion ◽  
Entire Sequence ◽  
June July ◽  
Earthquake Sequences

abstract An earthquake of magnitude ML 4.5 occurred on June 20, 1976 in an area of complex faulting in northeastern California, near the intersection of the Sierra Nevada, Modoc Plateau, Cascade Range, and Basin and Range geological provinces. P-wave first motion plots for larger aftershocks of this earthquake indicate maximum and minimum compressive stress, respectively, in north-south and east-west directions, with predominantly strike-slip motion. Focal depths for these events ranged from 7 to 15 km, consistent with other earthquake sequences in the region. Origin times of more than 4,700 aftershocks for the period between June 20 and July 1 are compared with the phase of solid-earth tidal components appropriate for normal and shear stress on northeast- and northwest-trending fault planes. Based on this comparison, approximately 20 per cent more earthquakes occurred at times when the normal compressive stress on the fault plane was decreasing, and the shear stress was increasing in the sense of slip on the fault plane. This correlation may be explained by two large bursts of aftershocks that occurred at times when tidal stresses were favorable for motion on the fault plane, rather than continuous triggering of small events during the entire sequence.

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