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Development of a sensitive, robust earth-resistivity measurement system stable over long period to monitor subtle temporal change in stress in the Earth’s crust
Published in H. Ogasawara, T. Yanagidani, M. Ando, Seismogenic Process Monitoring, 2017
Futoshi Yamashita, Takashi Yanagidani
It is important to monitor the stress state of rock surrounding active faults, since it should be related to the earthquake cycle that consists of a slow build-up of secular stress and a sudden decrease in stress. Even on a quiescent fault, slow and steady stress build-up occurs toward the next earthquake. However, the change in the stress state is too slow and small to be detected by usual procedures, such as stress relief (e.g. Merrill & Peterson 1961), hydraulic fracturing (e.g. Zoback et al. 1977), and borehole breakout research (e.g. Vernik & Zoback 1992). In order to detect slow and small change in stress, some physical quantities that are sensitive to stress, such as the electrical resistivity of rock, need to be precisely monitored.
SUPERCOMPUTER APPLICATIONS
Published in Franklin Y. Cheng, FU Zizhi, Computational Mechanics in Structural Engineering, 2003
CHARLES R. FARRAR, CHARLES A. ANDERSON
Figure 11 shows the elastic thickness-averaged fault parallel velocity (normalized by Vp) at 8.7 years into a 160-year earthquake cycle vs perpendicular distance from the fault (normalized by the elastic layer thickness) for the Li and Rice model and the numerical model (the numerical model was run for 5 cycles and the results plotted for corresponding times in the fifth cycle, i.e., 648.7 years = 4 x 160 years + 8.7 years). Agreement between the numerical and approximate analytic models is excellent at three given times during the earthquake cycle.
Earthquake Precursory Studies in India
Published in Ramesh P. Singh, Darius Bartlett, Natural Hazards, 2018
Brijesh K. Bansal, Mithila Verma
Examination of radon variations in a closed-air column shows a number of sporadic fluctuations, but two sharp bell changes marked by well-developed negative and positive excursions were distinct features around the Kharsali Earthquake (Choubey et al. 2009). The magnitudes of both positive and negative show an anomalous pattern, statistically significant, as extreme values deviated by more than two standard deviations from the seasonal mean. This was the first anomalous pattern observed on 26 June 2009, approximately 23 days before the occurrence of the Kharsali Earthquake, whereas the second anomalous pattern was recorded a few hours before the event. In comparison, the radon concentration in water shows slow and smooth changes that correlate better with water level fluctuations in the borehole. Considering sharp radon changes in the air column to be characteristic of the precursory signal to an earthquake, an empirical relation incorporating the observed amplitude of the radon peak, decay rate and average prevailing values of radon concentration estimated the magnitude of the impending earthquake as close to 4.6–4.7, in fair agreement with the observed magnitude of the Kharsali Earthquake (Mw 5.0) on 22 July 2007. While this example reinforced the physical rationale that there exists an association between stress build up during an earthquake cycle and radon flux, further validation was emphasized in view of the fact that some of the recorded sharp changes in radon intensity coincided with intense rainfall, groundwater fluctuations and fluctuation in pressure and temperature (Arora et al. 2012b). In a recent communication, Kumar et al. (2017) report anomalous radon gas emission observed in soil and water at the Ghuttu MPGO for the Mw 7.8 Nepal earthquake of 25 April 2016. The earthquake occurred ~600 km to the east of the observatory, and radon emission measured at 50 m depth using a gamma probe showed a prominent pre-seismic temporal change similar to that of soil radon.
An alternative to the fault-valve model
Published in Australian Journal of Earth Sciences, 2023
A complete description of the dynamics of the dissolution deposition cycle requires consideration of the coupled mass and energy budgets of the system. In particular, coupling to the temperature changes that accompany the process needs to be considered. Some aspects of such coupling are in Hobbs and Ord (2018), Ord and Hobbs (2018) and Poulet et al. (2014). The dissolution of quartz is endothermic, and the deposition is exothermic, as are the deformation and the mineral reactions that lead to negative ΔV and laminated vein formation. These endothermic exothermic processes compete and lead to fluctuations in fluid pressure, so they play important roles in the dynamics of the overall process. In addition, reactions such as that depicted in Figure 5 absorb fluids and so compete with the supply of fluid for the pressure solution/transfer processes. Poulet et al. (2014) discuss the relation of such coupled processes to the slow earthquake cycle, and so there is probably a link to seismicity and aseismic slip through such coupling processes.
Paleoseismology of the Hyde Fault, Otago, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2022
Jonathan D. Griffin, Mark W. Stirling, David J.A. Barrell, Ella J. van den Berg, Erin K. Todd, Ross Nicolls, Ningsheng Wang
Episodic earthquake recurrence in Otago is consistent with observations from many low activity rate faults globally (e.g. Clark et al. 2012), particularly for reverse faults, and is not easily explained by the standard earthquake cycle model of regular strain accumulation and release (Calais et al. 2016; Griffin et al. 2020b). Developing a better understanding of the variability of earthquake inter-event times on faults within Otago, and whether episodic recurrence is a ubiquitous feature within the system, has important implications for seismic hazard assessment (e.g. Stirling et al. 2012). How best to characterise the distribution of earthquake inter-event times for faults that demonstrate episodic earthquake activity is presently a major source of uncertainty for seismic hazard assessment, particularly on low activity-rate faults (Stirling et al. 2011; Coppersmith et al. 2012; Petersen et al. 2015; Allen et al. 2020; Morell et al. 2020; Taylor-Silva et al. 2020; Griffin et al. 2020a; Stirling et al. 2021).
Seismic Load Capacity of Historical Masonry Mosques by Rigid Body Kinetics
Published in International Journal of Architectural Heritage, 2020
Irfan Kocaman, Ilker Kazaz, Emriye Kazaz
North wall is under compression in the earthquake cycle that causes the mosque to collapse as shown Figure 12a, previously. The wall is exposed to axial force of 10804 kN (Wd) due to its own weight and 2847 kN (Wup) due to dome. Using Equation (6), the dynamic axial force (Ne) was calculated as 6062 kN. As shown in Figure 12a, the intersection areas and even small parts of the east and west walls breaking from the window openings participate in the overturning motion of the north wall. The west and east walls which are perpendicular to the north and south walls, behaves as restraining support when the north and south walls move inwards the structure. But the west and east walls loses their restraining effect when the north and south walls move outwards the structure, as displayed in Figure 12a. Knowing that mass is uniformly distributed along the height of the walls, distribution of dynamic forces acting on the north wall can be regarded as triangular. It is possible to get he = 0.67hwall in this way. Using these values, the out-of-plane load capacity to the north wall can be calculated by Equation (5) as