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1.
Probabilistic seismic hazard analysis (PSHA) has been carried out for Iraq. The earthquake catalogue used in the present study covers an area between latitude 29°–38.5° N and longitude 39°–50° E containing more than a thousand events for the period 1905–2000. The entire Iraq region has been divided into thirteen seismogenic sources based on their seismic characteristics, geological setting and tectonic framework. The completeness of the seismicity catalogue has been checked using the method proposed by Stepp (1972). The analysis of completeness shows that the earthquake catalogue is not complete below Ms=4.8 for all of Iraq and seismic source zones S1, S4, S5, and S8, while it varies for the other seismic zones. A statistical treatment of completeness of the data file was carried out in each of the magnitude classes. The Frequency Magnitude Distributions (FMD) for the study area including all seismic source zones were established and the minimum magnitude of complete reporting (Mc) were then estimated. For the entire Iraq the Mc was estimated to be about Ms=4.0 while S11 shows the lowest Mc to be about Ms=3.5 and the highest Mc of about Ms=4.2 was observed for S4. The earthquake activity parameters (activity rate , b value, maximum regional magnitude mmax) as well as the mean return period (R) with a certain lower magnitude mmin m along with their probability of occurrence have been determined for all thirteen seismic source zones of Iraq. The maximum regional magnitude mmax was estimated as 7.87 ± 0.86 for entire Iraq. The return period for magnitude 6.0 is largest for source zone S3 which is estimated to be 705 years while the smallest value is estimated as 9.9 years for all of Iraq.The large variation of the b parameter and the hazard level from zone to zone reflects crustal heterogeneity and the high seismotectonic complexity. The seismic hazard near the source boundaries is directly and strongly affected by the change in the delineation of these boundaries. The forces, through which the geological structure along the plate boundary in Eastern and Northeastern Iraq are evolved, are still active causing stress-strain accumulation, deformation and in turn producing higher probabilities of earthquake activity. Thus, relatively large destructive earthquakes are expected in this region. The study is intended to serve as a reference for more advanced approaches and to pave the path for the probabilistic assessment of seismic hazard in this region. 相似文献
2.
We present an uncertainty analysis of ecological process parameters and CO2 flux components (R
eco, NEE and gross ecosystem exchange (GEE)) derived from 3 years’ continuous eddy covariance measurements of CO2 fluxes at subtropical evergreen coniferous plantation, Qianyanzhou of ChinaFlux. Daily-differencing approach was used to
analyze the random error of CO2 fluxes measurements and bootstrapping method was used to quantify the uncertainties of three CO2 flux components. In addition, we evaluated different models and optimization methods in influencing estimation of key parameters
and CO2 flux components. The results show that: (1) Random flux error more closely follows a double-exponential (Laplace), rather
than a normal (Gaussian) distribution. (2) Different optimization methods result in different estimates of model parameters.
Uncertainties of parameters estimated by the maximum likelihood estimation (MLE) are lower than those derived from ordinary
least square method (OLS). (3) The differences between simulated Reco, NEE and GEE derived from MLE and those derived from OLS are 12.18% (176 g C·m−2·a−1), 34.33% (79 g C·m−2·a−1) and 5.4% (92 g C·m−2·a−1). However, for a given parameter optimization method, a temperature-dependent model (T_model) and the models derived from
a temperature and water-dependent model (TW_model) are 1.31% (17.8 g C·m−2·a−1), 2.1% (5.7 g C·m−2·a−1), and 0.26% (4.3 g C·m−2·a−1), respectively, which suggested that the optimization methods are more important than the ecological models in influencing
uncertainty in estimated carbon fluxes. (4) The relative uncertainty of CO2 flux derived from OLS is higher than that from MLE, and the uncertainty is related to timescale, that is, the larger the
timescale, the smaller the uncertainty. The relative uncertainties of Reco, NEE and GEE are 4%−8%, 7%−22% and 2%−4% respectively at annual timescale.
Supported by the National Natural Science Foundation of China (Grant No. 30570347), Innovative Research International Partnership
Project of the Chinese Academy of Sciences (Grant No. CXTD-Z2005-1) and National Basic Research Program of China (Grant No.
2002CB412502) 相似文献
3.
Starting from the classical empirical magnitude-energy relationships, in this article, the derivation of the modern scales
for moment magnitude M
w and energy magnitude M
e is outlined and critically discussed. The formulas for M
w and M
e calculation are presented in a way that reveals, besides the contributions of the physically defined measurement parameters
seismic moment M
0 and radiated seismic energy E
S, the role of the constants in the classical Gutenberg–Richter magnitude–energy relationship. Further, it is shown that M
w and M
e are linked via the parameter Θ = log(E
S/M
0), and the formula for M
e can be written as M
e = M
w + (Θ + 4.7)/1.5. This relationship directly links M
e with M
w via their common scaling to classical magnitudes and, at the same time, highlights the reason why M
w and M
e can significantly differ. In fact, Θ is assumed to be constant when calculating M
w. However, variations over three to four orders of magnitude in stress drop Δσ (as well as related variations in rupture velocity V
R and seismic wave radiation efficiency η
R) are responsible for the large variability of actual Θ values of earthquakes. As a result, for the same earthquake, M
e may sometimes differ by more than one magnitude unit from M
w. Such a difference is highly relevant when assessing the actual damage potential associated with a given earthquake, because
it expresses rather different static and dynamic source properties. While M
w is most appropriate for estimating the earthquake size (i.e., the product of rupture area times average displacement) and
thus the potential tsunami hazard posed by strong and great earthquakes in marine environs, M
e is more suitable than M
w for assessing the potential hazard of damage due to strong ground shaking, i.e., the earthquake strength. Therefore, whenever
possible, these two magnitudes should be both independently determined and jointly considered. Usually, only M
w is taken as a unified magnitude in many seismological applications (ShakeMap, seismic hazard studies, etc.) since procedures
to calculate it are well developed and accepted to be stable with small uncertainty. For many reasons, procedures for E
S and M
e calculation are affected by a larger uncertainty and are currently not yet available for all global earthquakes. Thus, despite
the physical importance of E
S in characterizing the seismic source, the use of M
e has been limited so far to the detriment of quicker and more complete rough estimates of both earthquake size and strength
and their causal relationships. Further studies are needed to improve E
S estimations in order to allow M
e to be extensively used as an important complement to M
w in common seismological practice and its applications. 相似文献
4.
This paper presents a robust H∞ output feedback control approach for structural systems with uncertainties in model parameters by using available acceleration measurements and proposes conditions for the existence of such a robust output feedback controller. The uncertainties of structural stiffness, damping and mass parameters are assumed to be norm-bounded. The proposed control approach is formulated within the framework of linear matrix inequalities, for which existing convex optimization techniques, such as the LMI toolbox in MATLAB, can be used effectively and conveniently. To illustrate the effectiveness of the proposed robust H∞ strategy, a six-story building was subjected both to the 1940 El Centro earthquake record and to a suddenly applied Kanai-Tajimi filtered white noise random excitation. The results show that the proposed robust H∞ controller provides satisfactory results with or without variation of the structural stiffness, damping and mass parameters. 相似文献
5.
Turhan Dogan Toshiya Mori Fumiaki Tsunomori Kenji Notsu 《Pure and Applied Geophysics》2007,164(12):2449-2463
Soil H2 and CO2 surveys were carried out along seven active faults and around the aftershock region of the 2000 Tottori-ken Seibu earthquake
in Japan. Diffuse CO2 effluxes were also measured along one fault and around the 2000 aftershock region. The results show highly variable H2 concentration in space and time and it seems that the maximum H2 concentration at each active fault correlates with fault activity as exemplified by the time of the latest big earthquakes.
Even though observed H2 concentrations in four faults were markedly lower than those collected previously in the latter half of the 1970s, it is
evident that the higher H2 concentrations in this study are due to the addition of the fault gases. Comparing the chemical composition of trapped gases
(H2: 5–20% and CO2/H2: 0.5–12) in fractured rocks of drill cores bored at the Nojima fault, a soil gas sample with the highest H2 concentration showed large amounts of the trapped fault gas, diluted with atmospheric component. The profile experiment across
a fracture zone at the Yamasaki fault showed higher H2 concentrations and lower CO2/H2 ratios as was observed in soil gas from the fracture zone. A few days after the 2000 Tottori-kei Seibu earthquake, no CO2 effluxes related to the occurrence of earthquakes were observed at the aftershock region. However, only above the epicenter
zone, relatively high H2 concentrations in soil gases were observed. 相似文献
6.
Sliding-window cross-correlation method is firstly adopted to identify sPn phase, and to constrain focal depth from regional
seismograms, by measuring the time separation between sPn and Pn phases. We present the focal depths of the 17 moderate-sized
aftershocks (M
S⩾5.0) of the Wenchuan M
S8.0 earthquake, using the data recorded by the regional seismic broadband networks of Shaanxi, Qinghai, Gansu, Yunnan and
Sichuan. Our results show focal depths of aftershocks range from 8 to 20 km, and tend to cluster at two average depths, separate
at 32.5°N, i.e., 11 km to the south and 17 km to the north, indicating that these aftershocks are origin of upper-to-middle
crust. Combined with other results, we suggest that the Longmenshan fault is not a through-going crustal fault and the Pingwu-Qingchuan
fault may be not the northward extension of the Longmenshan thrust fault.
Supported by the National Natural Science Foundation of China (Grant Nos. 40604009 and 40574040) and Special Project for the
Fundamental R & D of Institute of Geophysics, China Earthquake Administration (Grant No.DQJB08B20) 相似文献
7.
785 traces of vertical components from shallow earthquakes recorded by 10 CDSN (Chinese Digital Seismographic Network) stations
and 5 GSN (Global Seismographic Network) stations were collected to study the attenuation characteristics ofL
g coda in the Chinese continent and its adjacent regions. The records were processed first using the stack spectral ratio method
to obtain the average values ofQ
0 (Q at 1Hz) and η, the frequency dependence, ofL
g coda in the ellipses corresponding to the paths. The back-projection technique was then employed to obtain the tomographic
maps ofQ
0 and η values, and the distribution of their errors. Results indicate that in the studied areaQ
0 varies between 200 and 500. The lowest value ofQ
0 exists in the Yun-nan-Tibetan region, while the highest value ofQ
0 occurs in the southern edge of Siberian platform. η varies between 0.3 and 0.8. For most part of the studied area η varies
inversely withQ
0. 相似文献
8.
The static closed chamber technique is used in the study on the CH4 and N2O fluxes from the soils of primeval Abies fabri forest, the succession Abies fabri forest and the clear-cut areas of mid-aged Abies fabri forest in the Gongga Mountain from May 1998 to September 1999. The results indicate the following: (i) The forest soil serves
as the source of atmospheric N2O at the three measurement sites, while the fluxes of CH4 are all negative, and soil is the sink of atmospheric CH4. The comparative relations of N2O emissions between the three sites are expressed as primeval Abies fabri forest < clear-cut areas < succession Abies fabri forest, and those of CH4 consumption fluxes are primeval Abies fabri forest < succession Abies fabri forest < clear-cut areas, (ii) Significant seasonal variations of N2O emission at various sites were observed, and two emission peaks of N2O occurr during summer (July—August) and spring (February—March), whereas N2O emission is relatively low in winter and spring (mid March—April). Seasonal variations of CH4 consumption at each measurement site fluctuate drastically with unclear regularities. Generally, CH4 consumption fluxes of succession Abies fabri forest and clear-cut areas are higher from mid May to late July but lower in the rest of sampling time, while the CH4 flux keeps a relatively high value even up to September in primeval Abies fabri forest. In contrast to primeval Abies fabri forest, the CH4 absorbabilities of succession Abies fabri forest and clear-cut areas of mid-aged Abies fabri forest are weaker. Particularly, the absorbability of the clear-cut areas is even weaker as compared with the other two sites,
for the deforestation reduces the soil absorbability of atmospheric CH4. (iii) Evident diurnal variation regularity exists in the N2O emissions of primeval Abies fabri forest, and there is a statistic positive correlation between the fluxes of N2O and air temperature (R=0.95, n=11, α· 0.01), and also the soil temperature of 5-cm layer (R=0.81, n=11, α> 0.01), whereas the CH4 diurnal variation regularities are unclear and have no significant correlation with the soil temperature of 5-cm layer and
air temperature. 相似文献
9.
Toru Ouchi 《地震学报(英文版)》1997,10(6):727-730
The earthquake size distribution is generally considered to obey the Gutenberg-Richter (GR) law. We have introduced the concept
of the b value spectrum based on the moment method to investigate the deviation of the actual magnitude distribution of earthquakes
from this law. This enables us to describe characteristic features of the magnitude frequency distribution of earthquakes.
We found also a simple relation between the η value and the b value spectrum. Analysis using this scheme showed that the actual size distributions of earthquakes have large variations
from case to case and sometimes deviate considerably from the widely assumed the GR formula. 相似文献
10.
Allison L. Bent 《Pure and Applied Geophysics》1996,146(1):5-20
The Timiskaming earthquake, which occurred near the Quebec-Ontario border at the northwest end of the Western Quebec seismic zone in 1935, is one of the five largest instrumentally recorded southeastern Canadian earthquakes. Previous studies of this earthquake concentrated on modeling teismograms recorded at regional distances, a better constrained focal mechanism is obtained. The waveforms indicate thrust faulting on a moderately dipping northwest striking plane at a depth of 10 km. TheM
w
of 6.1 determined in this study is in good agreement with previous magnitude estimates (m
b
6.1,M
s
6.0, andm
bLg
6.2–6.3). The focal mechanism is similar to those of many recent small to moderate earthquakes in the region, and the inferred (from theP axis) acting stress of northeast compression is consistent with the overall eastern North American stress field. The Lake Timiskaming Rift Valley in which the earthquake occurred, comprises several northwest striking faults consistent with the strike of the 1935 event. Thus, the 1935 earthquake appears to be a result of faulting on the reactivated Timiskaming graben. 相似文献
11.
The work presents statistical methods for estimating the distribution parameters of rare, strong earthquakes. Using the two
main theorems of extreme value theory (EVT), the distribution of T-maximum (the maximum magnitude over the time period T). Two methods for estimating the parameters of this distribution are proposed using the Generalized Pareto Distribution (GPD)
and the General Extreme Value Distribution (GEV). In addition, the that allow the determination of the distribution of the
T-maximum for an arbitrary value of T are proposed. The approach being used clarifies the nature of the instability of the widely accepted M max parameter. In the work, instead of unstable values of the M max parameter, the robust parameter Q
T
(q), the q level quantile for the distribution of the T-maximum, is proposed to be used. The described method has been applied to the Harvard Catalogue of Seismic Moments of 1977–2006
and to the Magnitude Catalogue for Fennoscandia in 1900–2005. Moreover, the estimates of parameters of the corresponding GPD
and GEV distributions, in particular, the most interesting shape parameter and the values of the M
max and Q
T
(q) parameters are given. 相似文献
12.
Ya. B. Radziminovich V. S. Imaev N. A. Radziminovich V. V. Ruzhich O. P. Smekalin A. V. Chipizubov 《Seismic Instruments》2010,46(2):107-120
In this work, the macroseismic effects of the Kultuk earthquake (M
W = 6.3), which took place on August 27, 2008 in the southwestern closure of the Baikal Lake, are under consideration. The
intensity of shocks in inhabited localities located in the epicentral zone reached 7–8 points on the MSK-64 scale. The earthquake
was named after the local settlement of Kultuk, which was the mostly damaged area by the earthquake. The considered seismic
event caused significant material damage (about 250 million rubles according to preliminary estimates). In inhabited localities
of Southern Pribaikalie thousands of cases of damaged ovens and chimneys were registered. Some buildings were highly damaged
and, accordingly, they are unfit for further use. The earthquake was the cause of numerous rockslides, rockfalls, and landslides
on steep natural and artificial slopes. A macroseismic survey allowed us to establish the asymmetrical distribution of the
intensity of shocks relative to the epicenter. 相似文献
13.
In this paper, authors obtain the spectral peaks of the earth free oscillation and check all normal modes from 0S0 to 0S48 accurately, with the Fourier analysis and the maximum entropy spectrum method dealing jointly with six groups of the observational
residual data from five international superconducting gravimeter stations. By comparing the observational results in this
paper with three former groups of observations or models, authors notice an extra discrepancy between two observational 0S2 modes excited separately by Peru earthquake and Alaska earthquake, which probably mirrors the anisotropy of the Earth’s inner
core. The analysis on the splitting 1S2 mode shows that the asymmetric factor of rotationwise spectral splitting is possible to be different from that of anti-rotationwise
spectral splitting. 相似文献
14.
Parametric-historic Procedure for Probabilistic Seismic Hazard Analysis Part I: Estimation of Maximum Regional Magnitude mmax 总被引：1，自引：0，他引：1
—A new methodology for probabilistic seismic hazard analysis (PSHA) is described. The approach combines the best features of the "deductive" (Cornell, 1968) and "historical" (Veneziano et al., 1984) procedures. It can be called a "parametric-historic" procedure.¶The maximum regional magnitude m max is of paramount importance in this approach and Part I of our work presents some of the statistical techniques which can be used for its evaluation. The work is an analysis of parametric procedures for the evaluation of m max, when the form of the magnitude distribution is specified. For each of the formulae given there are notes on its origin, assumptions made of its derivation, and some comparisons. The statistical concepts of bias and variance are considered for each formula, and appropriate expressions for these are also given. Also, following Knopoff and Kagan (1977), we shall demonstrate why there must be a finite upper bound to the largest seismic event if the Gutenberg-Richter frequency-magnitude relation is accepted. 相似文献
15.
Most of the present earthquake early warning systems are based on broadband or strong motion recordings. How-ever, the short-period instruments are still deployed. It is well-known that short-period recordings have saturation problems for large earthquakes when estimating the size of an earthquake. Thus, it is necessary to make clear the magnitude at which saturation starts to occur for the commonly used τc and Pd measurements, respectively. To investigate the possibility of using short-period seismic recordings for earthquake early warning, we conducted a simulated experiment using the strong motion data of the 1999 Chi-Chi earthquake sequence including its main shock and 31 aftershocks, with magnitude span from 4 to 7.6. The strong motion acceleration recordings were convolved with the instrument response of short-period seismographs in northern China to simulate short-period seismograms. Parameters τc and Pd from the first-three-second seismograms were calculated for the simulated short-period recordings and compared with that obtained by the original strong ground motion recordings. The result showed that to some extent, short-period recordings can be used for threshold earthquake early warning, while the magnitude saturation of Pd estimation can be up to 6.5, better than τc estimation. 相似文献
16.
17.
The stability of the power law scaling of earthquake recurrence time distribution in a given space–time window is investigated,
taking into account the magnitude of completeness and the effective starting time of aftershock sequences in earthquake catalogs
from Southern California and Japan. A new method is introduced for sampling at different distances from a network of target
events. This method allows the recurrence times to be sampled many times on the same area. Two power laws with unknown exponents
are assumed to govern short- and long-recurrence-time ranges. This assumption is developed analytically and shown to imply
simple correlation between these power laws. In practice, the results show that this correlation structure is not satisfied
for short magnitude cutoffs (m
c
= 2.5, 3.5, 4.5), and hence the recurrence time distribution departs from the power law scaling. The scaling parameters obtained
from the stack of the distributions corresponding to different magnitude thresholds are quite different for different regions
of study. It is also found that significantly different scaling parameters adjust the distribution for different magnitude
thresholds. In particular, the power law exponents decrease when the magnitude cutoff increases, resulting in a slower decrease
of the recurrence time distribution, especially for short time ranges. For example, in the case of Japan, the exponent p2 of the power law scaling at large recurrence times follows roughly the relation: , where m
c
is the magnitude cutoff. In case of Southern California, it is shown that Weibull distribution provides a better alternative
fit to the data for moderate and large time scales. 相似文献
18.
本文选取2013年芦山地震和2017年九寨沟地震波形,重新量取垂直向振幅,计算宽频带面波震级MS（BB）,分析各台站实测震级出现方向性差异的原因。其中,通过572个宽频带台站实测芦山地震震级MS（BB）7.1,通过603个宽频带台站实测九寨沟地震震级MS（BB）6.9。芦山地震实测震级大于MS（BB）7.3的台站呈现WN-ES向分布,与断层倾向一致;实测震级小于MS（BB）7.0的台站呈现NE-WS向分布,与其所在断层走向一致。九寨沟地震实测震级大于MS（BB）7.0的台站分布呈现NE向分布,与断层倾向一致;实测震级小于MS（BB）6.8的台站总体分布较为离散,大体呈现NW-SE向分布,与树正断裂走向一致。实测震级偏大的台站方向性分布与多普勒效应和P波辐射花样联系不明显。对比分析芦山地震和九寨沟地震,去除场地响应和仪器自身影响,台站实测震级差异性仍然存在,因此,台站实测震级差异性是由于受到了多普勒效应、辐射花样、仪器和场地响应之外的因素影响。综合考虑地震震级涉及的影响因素,芦山地震和九寨沟地震的台站实测震级差异性可能与地震波的传播路径有关。 相似文献
19.
Using 116 earthquakes over M_L3.8 in the Inner Mongolia region from 2008 to 2015, the local earthquake magnitude M_L and surface wave magnitude M_S are remeasured. Based on norm linear regression(SR1 and SR2) and norm(OR) orthogonal regression method, we established the conversion relationship between M_L and M_S. The results were tested with Gaussian disturbance. The result shows that the orthogonal regression method(OR) result has the best fitting curve, and the conversion relation is M_S=0.96 M_L-0.10. The difference between our result and Guo Lücan's(M_S=1.13 M_L-1.08) may be caused by regional tectonic characteristics. M_(S Inner Mongolia) value is significantly higher than the M_(S empirical) value, with an average difference of 0.23, the difference distribution of empirical relation and the rectified relation is in the range of 0.2-0.3. 相似文献
20.
Characteristics of the pCO2 distribution in surface water of the Bering Abyssal Plain and their relationships with the ambient hydrological conditions
were discussed using variations of the partial pressure of CO2 in surface water of the Bering Abyssal Plain and the Chukchi Sea. Data in this study are from a field investigation during
the First Chinese National Arctic Research Expedition in 1999. Compared to the high productivity in the Bering Continental
Shelf, much lower levels of chlorophyll a were observed in the Bering Abyssal Plain. The effect of hydrological factors on
the pCO2 distribution in surface seawater of the Plain in summer has become a major driving force and dominated over biological factors.
The Plain also presents a High Nutrient Low Chlorophyll (HNLC). In addition, the pCO2 distribution in the Bering Abyssal Plain has also been found to be influenced from the Bering Slope Current which would transform
to the Anadyr Current when it inflows northwestward over the Plain. The Anadyr Current would bring a high nutrient water to
the western Arctic Ocean where local nutrients are almost depleted in the surface water during the summer time. Resupplying
nutrients would stimulate the growth of phytoplankton and enhance capacity of absorbing atmospheric CO2 in the surface water. Otherwise, in the Bering Sea the dissolved inorganic carbon brought from freshwater are not deposited
down to the deep sea water but most of them would be transported into the western Arctic Ocean by the Alaska Coastal Current
to form a carbon sink there. Therefore, the two carbon sinks in the western Arctic Ocean, one carried by the Anadyr Current
and another by the Alaska Costal Current, will implicate the western Arctic Ocean in global change. 相似文献