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31.
Mathematical Geosciences - 相似文献
32.
A regional time and magnitude predictable model has been applied to estimate the recurrence intervals for large earthquakes
in the vicinity of 8 October 2005 Kashmir Himalaya earthquake (25°–40°N and 65°–85°E), which includes India, Pakistan, Afghanistan,
Hindukush, Pamirs, Mangolia and Tien-Shan. This region has been divided into 17 seismogenic sources on the basis of certain
seismotectonics and geomorphological criteria. A complete earthquake catalogue (historical and instrumental) of magnitude
Ms ≥ 5.5 during the period 1853–2005 has been used in the analysis. According to this model, the magnitude of preceding earthquake
governs the time of occurrence and magnitude of future mainshock in the sequence. The interevent time between successive mainshocks
with magnitude equal to or greater than a minimum magnitude threshold were considered and used for long-term earthquake prediction
in each of seismogenic sources. The interevent times and magnitudes of mainshocks have been used to determine the following
predictive relations: logT
t = 0.05 M
min + 0.09 M
p − 0.01 log M
0 + 01.14; and M
f = 0.21 M
min − 0.01 M
p + 0.03 log M
0 + 7.21 where, T
t is the interevent time of successive mainshocks, M
min is minimum magnitude threshold considered, M
p is magnitude of preceding mainshock, M
f is magnitude of following mainshock and M
0 is the seismic moment released per year in each seismogenic source. It was found that the magnitude of following mainshock
(M
f) does not depend on the interevent time (T
t), which indicates the ability to predict the time of occurrence of future mainshock. A negative correlation between magnitude
of following mainshock (M
f) and preceding mainshock (M
p) indicates that the larger earthquake is followed by smaller one and vice versa. The above equations have been used for the
seismic hazard assessment in the considered region. Based on the model applicability in the studied region and taking into
account the occurrence time and magnitude of last mainshock in each seismogenic source, the time-dependent conditional probabilities
(PC) for the occurrence of next shallow large mainshocks (Ms ≥ 6.5), during next 20 years as well as the expected magnitudes
have been estimated. 相似文献
33.
Uplift capacity of single piles: predictions and performance 总被引：4，自引：0，他引：4
The paper pertains to the development of a simple semi-empirical model for predicting the uplift capacity of piles embedded
in sand. Various pile and soil parameters such as length (L), diameter (d) of the pile and angle of friction (ϕ), soil–pile friction angle (δ) and unit weight (γ) of the soil which have direct influence
on the uplift capacity of the pile are incorporated in the analysis. A comparative assessment of the ultimate uplift capacity
of piles predicted by using the proposed theory and some of the available theories are made with respect to each other and
with reference to the measured values obtained from model tests in the laboratory. For this purpose experimental data have
been collected from the literature and also from model tests conducted as a part of the present investigation. The study shows
the proposed model has an excellent potential in predicting the uplift capacity of piles embedded in sand that are consistent
with model pile test results. 相似文献
34.
The seismic characteristic of Hindukush–Pamir–Himalaya (HPH) and its vicinity is very peculiar and has experienced many widely distributed large earthquakes. Recent work on the time-dependent seismicity in the Hindukush–Pamir–Himalayas is mainly based on the so-called “regional time-predictable model”, which is expressed by the relation log T=cMp+a, where T is the inter-event time between two successive main shocks of a region and Mp is the magnitude of the preceded main shock. Parameter a is a function of the magnitude of the minimum earthquake considered and of the tectonic loading and c is positive (0.3) constant. In 90% of the cases with sufficient data, parameter c was found to be positive, which strongly supports the validity of the model. In the present study, a different approach, which assumes no prior regionalization of the area, is attempted to check the validity of the model. Nine seismic sources were defined within the considered region and the inter-event time of strong shallow main shock were determined and used for each source in an attempt at long-term prediction, which show the clustering and occurrence of at least three earthquakes of magnitude 5.5≤Ms≤7.5 giving two repeat times, satisfying the necessary and sufficient conditions of time-predictable model (TP model). Further, using the global applicability of the regional time- and magnitude-predictable model, the following relations have been obtained: log Tt=0.19 Mmin+0.52Mp+0.29 log m0−10.63 and Mf=1.31Mmin−0.60Mp−0.72 log m0+21.01, where Tt is the inter-event time, measured in years; Mmin the surface wave magnitude of the smallest main shock considered; Mp the magnitude of preceding main shock; Mf the magnitude of the following main shock; and m0 the moment rate in each source per year.
These relations may be used for seismic hazard assessment in the region. Based on these relations and taking into account the time of occurrence and the magnitude of the last main shock in each seismogenic source, time-dependent conditional probabilities for the occurrence of the next large (Ms≥5.5) shallow main shocks during the next 20 years as well as the magnitudes of the expected main shocks are determined. 相似文献
35.
—The maximum likelihood estimation of earthquake hazard parameters has been made in the Himalayas and its surrounding areas on the basis of a procedure which utilizes data containing complete files of the most recent earthquakes. The entire earthquake catalogue used covers the period from 1900–1990. The maximum regional magnitude M max?, the activity rate of the seismic event λ, the mean return period R of earthquakes with a certain lower magnitude M max≥ m along with their probability of occurrence, as well as the parameter b of of Gutenberg Richter magnitude-frequency relationship, have been determined for six different seismic zones of the Himalayas and its vicinity. It is shown that in general the hazard is higher in the zone NEI and BAN than the other four zones. The high difference of the b parameter and the hazard level from zone to zone reflect the high seismotectonic complexity and crustal heterogeneity. 相似文献
36.
The composite stereographic projection of orientations of the compression and tension axes using thirty-nine fault-plane solutions
of earthquakes from two active seismogenic sources of Nepal and adjoining areas were examined and the nature of stress pattern
and their influence on tectonics in the region have been studied. The seismogenic source located in Eastern Nepal region,
which has been the site of 1934 Bihar-Nepal great earthquake of M 8.4, is presently experiencing N-S to NE-SW directed compressive stresses. The inferred pattern of compression axes in Western
Nepal region suggests a shallow compressive stress, dipping N-S to NE-SW. Approximately similar nature of the stress regime
is observed in Western and Eastern regions of Nepal, separated by nearly 700 km; it shows N-S to NNE-SSW direction of compression
and underthrusting of the Indian Plate beneath the Himalaya at a shallow angle.
Present study indicates that the stress is being released along the strikes of some of the transverse faults present in the
region since the compressive stress exerted by the northward movement of the Indian Plate is approximately perpendicular to
the Himalayan collision belt. Unilateral stress pattern generated by the northward movement of the Indian Plate in the central
part of the Himalaya reveals that the present day collision occurs roughly perpendicular to the local strike of the Himalaya. 相似文献