Order parameter fluctuations in natural time and b-value variation before large earthquakes (original) (raw)
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Order Parameter and Entropy of Seismicity in Natural Time before Major Earthquakes: Recent Results
Geosciences
A lot of work in geosciences has been completed during the last decade on the analysis in the new concept of time, termed natural time, introduced in 2001. The main advances are presented, including, among others, the following: First, the direct experimental verification of the interconnection between a Seismic Electric Signals (SES) activity and seismicity, i.e., the order parameter fluctuations of seismicity exhibit a clearly detectable minimum when an SES activity starts. These two phenomena are also linked closely in space. Second, the identification of the epicentral area and the occurrence time of an impending major earthquake (EQ) by means of the order parameter of seismicity and the entropy change of seismicity under time reversal as well as the extrema of their fluctuations. An indicative example is the M9 Tohoku EQ in Japan on 11 March 2011. Third, to answer the crucial question—when a magnitude 7 class EQ occurs—whether it is a foreshock or a mainshock. This can be answe...
Entropy, 2020
It has been reported that major earthquakes are preceded by Seismic Electric Signals (SES). Observations show that in the natural time analysis of an earthquake (EQ) catalog, an SES activity starts when the fluctuations of the order parameter of seismicity exhibit a minimum. Fifteen distinct minima—observed simultaneously at two different natural time scales and deeper than a certain threshold—are found on analyzing the seismicity of Japan from 1 January 1984 to 11 March 2011 (the time of the M9 Tohoku EQ occurrence) 1 to 3 months before large EQs. Six (out of 15) of these minima preceded all shallow EQs of magnitude 7.6 or larger, while nine are followed by smaller EQs. The latter false positives can be excluded by a proper procedure (J. Geophys. Res. Space Physics 2014, 119, 9192–9206) that considers aspects of EQ networks based on similar activity patterns. These results are studied here by means of the receiver operating characteristics (ROC) technique by focusing on the area un...
Similarity of fluctuations in correlated systems: The case of seismicity
Physical Review E, 2005
We report a similarity of fluctuations in equilibrium critical phenomena and non-equilibrium systems, which is based on the concept of natural time. The world-wide seismicity as well as that of San Andreas fault system and Japan are analyzed. An order parameter is chosen and its fluctuations relative to the standard deviation of the distribution are studied. We find that the scaled distributions fall on the same curve, which interestingly exhibits, over four orders of magnitude, features similar to those in several equilibrium critical phenomena ( e.g., 2D Ising model) as well as in non-equilibrium systems (e.g., 3D turbulent flow).
Evidence for non-self-similarity in the Mw 7.7 2001 Bhuj earthquake sequence
Scaled energy, apparent stress, seismic moments, stress drops and corner frequencies are measured through the Levenberg-Marquardt nonlinear inversion modeling of S-wave displacement spectra for 489 selected earthquakes (M w 2.05-5.52) from the 2001 M w 7.7 Bhuj earthquake sequence. The iterative inversion scheme is formulated based on the x-square source spectral model, which enabled us to estimate stable source parameters. The estimated seismic moment (M o ) and source radius (r) vary from 1.5 9 10 12 to 2.4 9 10 17 to N m and 139.1-933.9 m, respectively, while estimated stress drops (Dr) and the multiplicative factor (E mo ) values range from 0.1 to 14.4 MPa and 1.0-4.1, respectively. The corner frequencies (f c ) are found to be ranging from 1.4 to 9.3 Hz. The mean standard deviation for f c , r and Dr are estimated to be 0.7 Hz, 91.4 m and 2.9 MPa, respectively. The radiated seismic energy and apparent stresses range from 2.1 9 10 5 to 4.1 9 10 13 Joule and 0.005-8.0 MPa, respectively. Our estimated corner frequencies and seismic moments satisfy the relation M o ? f c -(3?e) , where e (measure for a deviation from self-similarity) is found to be 1.33 for the larger earthquakes (M o C 2 9 10 15 N m), while the parameter e is estimated to be 6.74 for smaller earthquakes (M o \ 2 9 10 15 N m). We feel that the larger value of e may require to satisfy the increasing trend of scaled energy with moment for smaller earthquakes. We also notice that stress drops increase with seismic moment, approximately as Mo 3 (DrµM o 3 ) for smaller events (M o \ 10 15.3 N m), while for larger earthquakes (M o C 2 9 10 15 N m) stress drop increases approximately with M o 1 (DrµM o 1 )
Continuous-cyclic variations in the b-value of the earthquake frequency-magnitude distribution
Earthquake Science, 2013
Seismicity of the Earth (M C 4.5) was compiled from NEIC, IRIS and ISC catalogues and used to compute b-value based on various time windows. It is found that continuous cyclic b-variations occur on both long and short time scales, the latter being of much higher value and sometimes in excess of 0.7 of the absolute b-value. These variations occur not only yearly or monthly, but also daily. Before the occurrence of large earthquakes, b-values start increasing with variable gradients that are affected by foreshocks. In some cases, the gradient is reduced to zero or to a negative value a few days before the earthquake occurrence. In general, calculated b-values attain maxima 1 day before large earthquakes and minima soon after their occurrence. Both linear regression and maximum likelihood methods give correlatable, but variable results. It is found that an expanding time window technique from a fixed starting point is more effective in the study of b-variations. The calculated b-variations for the whole Earth, its hemispheres, quadrants and the epicentral regions of some large earthquakes are of both local and regional character, which may indicate that in such cases, the geodynamic processes acting within a certain region have a much regional effect within the Earth. The b-variations have long been known to vary with a number of local and regional factors including tectonic stresses. The results reported here indicate that geotectonic stress remains the most significant factor that controls b-variations. It is found that for earthquakes with M w C 7, an increase of about 0.20 in the b-value implies a stress increase that will result in an earthquake with a magnitude one unit higher.
Multiple-Time Scaling and Universal Behavior of the Earthquake Interevent Time Distribution
Physical Review Letters, 2010
The inter-event time distribution characterizes the temporal occurrence in seismic catalogs. Universal scaling properties of this distribution have been evidenced for entire catalogs and seismic sequences. Recently, these universal features have been questioned and some criticisms have been raised. We investigate the existence of universal scaling properties by analysing a Californian catalog and by means of numerical simulations of an epidemic-type model. We show that the inter-event time distribution exhibits a universal behaviour over the entire temporal range if four characteristic times are taken into account. The above analysis allows to identify the scaling form leading to universal behaviour and explains the observed deviations. Furthermore it provides a tool to identify the dependence on mainshock magnitude of the c parameter that fixes the onset of the power law decay in the Omori law. PACS numbers: 91.30.Px, 02.50.Ey, 89.75.Da, 91.30.Dk
Minimum of the order parameter fluctuations of seismicity before major earthquakes in Japan
Proceedings of the National Academy of Sciences, 2013
It has been shown that some dynamic features hidden in the time series of complex systems can be uncovered if we analyze them in a time domain called natural time χ . The order parameter of seismicity introduced in this time domain is the variance of χ weighted for normalized energy of each earthquake. Here, we analyze the Japan seismic catalog in natural time from January 1, 1984 to March 11, 2011, the day of the M9 Tohoku earthquake, by considering a sliding natural time window of fixed length comprised of the number of events that would occur in a few months. We find that the fluctuations of the order parameter of seismicity exhibit distinct minima a few months before all of the shallow earthquakes of magnitude 7.6 or larger that occurred during this 27-y period in the Japanese area. Among the minima, the minimum before the M9 Tohoku earthquake was the deepest. It appears that there are two kinds of minima, namely precursory and nonprecursory, to large earthquakes.
Correlation length as an indicator of critical point behavior prior to a large earthquake
Earth and Planetary Science Letters, 2005
A large earthquake preparation is often manifested in correlation of seismicity in an area whose characteristic dimension greatly exceeds a dimension of source of main shock. Zfller et al. [G. Zfller, S. Hainzl, J. Kurths, Observation of growing correlation length as an indicator for critical point behavior prior to large earthquakes, J. Geophys. Res. 106 (2001) 2167-2176] show the growth of correlation length of earthquakes prior to nine large earthquakes in California according to a power low. We argue that the algorithm of correlation length estimation proposed by Zfller et al. [G. Zfller, S. Hainzl, J. Kurths, Observation of growing correlation length as an indicator for critical point behavior prior to large earthquakes, J. Geophys. Res. 106 (2001) 2167-2176] can result in a decrease of correlation length preceding its precursory growth before large earthquakes if the area in which earthquake activity is correlated grows with time during a main shock preparation. The correlation length analysis of acoustic emission events recorded in laboratory experiments on destruction of rocks and correlation length analysis of intermediate magnitude earthquakes in the area of large earthquakes preparation on Kamchatka and in Italy confirms the theoretical argument. This effect can be considered as an additional premonitory pattern of large earthquake preparation. D 2004 Published by Elsevier B.V.
Influence of Time and Space Correlations on Earthquake Magnitude
Physical Review Letters, 2008
A crucial point in the debate on feasibility of earthquake prediction is the dependence of an earthquake magnitude from past seismicity. Indeed, whilst clustering in time and space is widely accepted, much more questionable is the existence of magnitude correlations. The standard approach generally assumes that magnitudes are independent and therefore in principle unpredictable. Here we show the existence of clustering in magnitude: earthquakes occur with higher probability close in time, space and magnitude to previous events. More precisely, the next earthquake tends to have a magnitude similar but smaller than the previous one. A dynamical scaling relation between magnitude, time and space distances reproduces the complex pattern of magnitude, spatial and temporal correlations observed in experimental seismic catalogs.