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1.
The aim of this work is to quantitatively set up a simple hypothesis for occurrence of earthquakes conditioned by prior events, on the basis of a previously existing model and the use of recent instrumental observations. A simple procedure is presented in order to determine the conditional probability of pairs of events (foreshock-mainshock, mainshock-aftershock) with short time and space separation. The first event of a pair should not be an aftershock, i.e., it must not be related to a stronger previous event. The Italian earthquake catalog of the Istituto Nazionale di Geofisica (ING) (1975–1995, M 3.4), the earthquake catalog of the Japan Meteorological Agency (JMA) (1983–1994, M 3.0) and that of the National Observatory of Athens (NOA) (1982–1994, M 3.8) were analyzed. The number of observed pairs depends on several parameters: the size of the space-time quiescence volume defining nonaftershocks, the inter event time, the minimum magnitude of the two events, and the spatial dimension of the alarm volume after the first event. The Akaike information criterion has been adopted to assess the optimum set of space-time parameters used in the definition of the pairs, assuming that the occurrence rate of subsequent events may be modeled by two Poisson processes with different rates: the higher rate refers to the space-time volume defined by the alarms and the lower one simulates earthquakes that occur in the nonalarm space-time volume. On the basis of the tests carried out on the seismic catalog of Italy, the occurrence rate of M 3.8 earthquakes followed by a M 3.8 mainshock within 10 km and 10 days (validity) is 0.459. We have observed, for all three catalogs, that the occurrence rate density for the second event of a couple (mainshock or aftershock) of magnitude M2 subsequent to a nonaftershock of magnitude M1 in the time range T can be modeled by the following relationship: (T, M2) = 10a + b(M1 - M2) with b varying from 0.74 (Japan) to 1.09 (Greece). The decrease of the occurrence rate in time for a mainshock after a foreshock or for large aftershocks after a mainshock, for all three databases, obeys the Omori's law with p changing from 0.94 (Italy) to 2.0 (Greece). 相似文献
2.
We construct a single hazard function from multiple predictive parameters independently developed for moderate earthquakes in Kanto, Japan, during a learning period from 1990 to 1999, and applied to a testing period from 2000 to 2005. Here, we consider as predictive parameters the a and b values of the Gutenberg–Richter relation, the ν value (change in b value), and the Every Earthquake a Precursor According to Scale (EEPAS) model rate. To study the correlations among the parameters, we prepare two groups of space–time coordinate sets for assessment, namely the background and conditional groups selected from the learning period. The background group contains ten thousand sets of coordinates randomly selected from the space–time volume of our study. The conditional group contains 33 sets of space–time coordinates corresponding to the epicenters of the target earthquakes (M ≥ 5.0) just before their times of occurrence. Each parameter for the background group is transformed so that its distribution conforms to the standard Normal function. The mean and variance of the conditional distribution is then estimated after applying the same transformation to the conditional group. Using the means and variances of b values, ν values and EEPAS rates and the correlation matrices in the background and conditional distributions, we construct a combined hazard function following the procedure developed for normally distributed parameters. The information gain per event (IGpe) of the new hazard function is 0.26 and 0.3 units larger than that of the EEPAS rate for the learning and testing period, respectively. The R-test confirms the statistical significance of the difference in the IGpe value for the testing period. 相似文献
3.
Multifractal analysis of spatial distribution of microearthquakes in the Kanto region 总被引：5，自引：0，他引：5
b
The spatial distribution of earthquakes is a fractal, which is characterized by a fractal dimension. However, if a spatial distribution has a heterogeneous fractal structure, a single value of fractal dimension [e.g. Do (capacity dimension) or D 2 (correlation dimension)] is not enough to characterize it. From a multifractal viewpoint, we analysed the spatial distribution of microearthquakes in the Kanto region by using a local density function. Generalized dimensions, Dq , of the spatial distribution were calculated from the slopes of generalized correlation integrals, Cq (r) versus distance r , on a log-log plot, examining the self-similarity of the spatial distribution of microearthquakes. Self-similar structures are held well at scales from 1.26 to 12.6 km. Our results suggest that the spatial distribution of microearthquakes in the Kanto region is not a homogeneous fractal structure but a heterogeneous one with generalized dimensions D2 = 2.2 ≤ D 3 ≤…≤ D ∞ = 1.7. The value of D ∞ , the lower limit of fractal dimension, is the fractal dimension of the most intensive clustering in the heterogeneous fractal set. The fractal dimension of the most intensive clustering of microearthquakes in the Kanto region is 1.7. 相似文献
The spatial distribution of earthquakes is a fractal, which is characterized by a fractal dimension. However, if a spatial distribution has a heterogeneous fractal structure, a single value of fractal dimension [e.g. D
4.
Determination of the role of entrapped air in water flow in a closed soil pipe using a laboratory experiment 
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下载免费PDF全文 Soil pipes, continuous macropores parallel to the soil surface, are an important factor in hillslope hydrological processes. However, the water flow dynamics in soil pipes, especially closed soil pipes, are not well understood. In this study, the water and air dynamics within closed soil pipes have been investigated in a bench‐scale laboratory experiment by using a soil box with an artificial acrylic soil pipe. In order to grasp the state of water and air within the soil pipe, we directly measured the existing soil pipe flow and air pressure in the soil pipe. The laboratory experiment showed that air in the soil pipe had an important role in the water flow in the closed soil pipe. When air entrapment occurred in the soil pipe before the soil matrix around the soil pipe was saturated with water, water intrusion in the soil pipe was prevented by air entrapped in the pipe, which inhibited the soil pipe flow. This air entrapment in the soil pipe was controlled by the soil water and air flow. Moreover, after the soil pipe flow started, the soil pipe was not filled completely with water even when the soil pipe was completely submerged under the groundwater table. The entrapped air in the soil pipe prevented further water intrusion in the soil pipe. 相似文献
5.
Efficient testing of earthquake forecasting models 总被引：1，自引：0，他引：1
David A. Rhoades Danijel Schorlemmer Matthew C. Gerstenberger Annemarie Christophersen J. Douglas Zechar Masajiro Imoto 《Acta Geophysica》2011,59(4):728-747
Computationally efficient alternatives are proposed to the likelihood-based tests employed by the Collaboratory for the Study
of Earthquake Predictability for assessing the performance of earthquake likelihood models in the earthquake forecast testing
centers. For the conditional L-test, which tests the consistency of the earthquake catalogue with a model, an exact test using convolutions of distributions
is available when the number of earthquakes in the test period is small, and the central limit theorem provides an approximate
test when the number of earthquakes is large. Similar methods are available for the R-test, which compares the likelihoods of two competing models. However, the R-test, like the N-test and L-test, is fundamentally a test of consistency of data with a model. We propose an alternative test, based on the classical
paired t-test, to more directly compare the likelihoods of two models. Although approximate and predicated on a normality assumption,
this new T-test is not computer-intensive, is easier to interpret than the R-test, and becomes increasingly dependable as the number of earthquakes increases. 相似文献
6.
7.
Grain growth kinetics and the effect of crystallographic anisotropy on normal grain growth of quartz
Katsuyoshi?MichibayashiEmail author Hisashi?Imoto 《Physics and Chemistry of Minerals》2012,39(3):213-218
Annealing experiments on agate were performed to investigate grain growth kinetics and the effect of crystallographic anisotropy
on normal grain growth of quartz. The experiments were conducted using a piston-cylinder apparatus at 700–800°C and 0.5 GPa
for 0–66 h. The grain growth rate was expressed by D
n
−D
0
n
= kt with k = k
0
exp(−H*/RT) where D
0
is the initial grain size at t = 0, with n = 4.4 ± 0.3, and H* = 191.3 ± 11.0 kJ/mol is the activation enthalpy and logk
0
= 19.8 ± 1.4. While the grain aspect ratios are nearly constant at ~0.7 (short/long) during grain growth, the longest axis
in individual grains tends to be oriented parallel to their c-axis, indicating that a primary crystal-preferred orientation of c-axis of the agate could result in the development of a weak shape-preferred orientation during grain growth. 相似文献
8.
9.
In the Kanto region, there have been reports of decreasing b-values prior to earthquakes (M ≥ 5.5). The change of b-values is defined as the difference between the long- and short-term average earthquake magnitudes. A hazard function for moderately large earthquakes has also been proposed. This model was based on earthquakes that occurred between 1982 and 1999, and its effectiveness is measured retrospectively. In order to evaluate the effectiveness of the model through the use of independent data, the verification test is based on earthquakes observed after January 2000. Through the end of 2004, the only event where there was a decrease in mean event size was observed on June 3, 2000. This decrease resulted in a log-likelihood for the proposed model 1.3 units larger than that of the Poisson model, supporting the validity of the proposed model. Without accumulating further examples, we attempted to improve the verification test by expanding the study volume and by lowering the target cutoff magnitude in order to overcome the small sample size. When two other targets from the expanded volume were added, the difference in the log-likelihood (ΔlnL) increased to 3.6. In this case, the information rate per event was about 1.2, larger than that of the model period. Lowering the cutoff magnitude increased ΔlnL to 2.5. These extended tests led to higher confidence in the model with the larger ΔlnL value than did the primary test. From the viewpoint of the per-event information rate, each case involving targets with a magnitude 5.5 and larger resulted in better performance than in the model period. 相似文献
10.