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1.
An automatic scheme for baseline correction of strong-motion records in coseismic deformation determination 总被引：2，自引：0，他引：2
Coseismic deformation can be determined from strong-motion records of large earthquakes. Iwan et al. (Bull Seismol Soc Am
75:1225–1246, 1985) showed that baseline corrections are often required to obtain reliable coseismic deformation because baseline offsets lead
to unrealistic permanent displacements. Boore (Bull Seismol Soc Am 91:1199–1211, 2001) demonstrated that different choices of time points for baseline correction can yield realistically looking displacements,
but with variable amplitudes. The baseline correction procedure of Wu and Wu (J Seismol 11:159–170, 2007) improved upon Iwan et al. (Bull Seismol Soc Am 75:1225–1246, 1985) and achieved stable results. However, their time points for baseline correction were chosen by a recursive process with
an artificial criterion. In this study, we follow the procedure of Wu and Wu (J Seismol 11:159–170, 2007) but use the ratio of energy distribution in accelerograms as the criterion to determine the time points of baseline correction
automatically, thus avoiding the manual choice of time points and speeding up the estimation of coseismic deformation. We
use the 1999 Chi-Chi earthquake in central Taiwan and the 2003 Chengkung and 2006 Taitung earthquakes in eastern Taiwan to
illustrate this new approach. Comparison between the results from this and previous studies shows that our new procedure is
suitable for quick and reliable determination of coseismic deformation from strong-motion records. 相似文献
2.
Vertical coseismic deformation on non-causative fault caused by remote strong earthquakes(epicentral distance≥1500 km,MS≥7.0)are observed by fault-monitoring instruments of new type during recent two years.The monitor-ing result shows,delay time,maximum amplitude and duration of vertical deformation on the non-causative faulthave remarkable close relationship with earthquakes magnitude and epicentral distance.The delay time of verticalcoseismic deformation have positive linear relationship with epicentral distance.The velocity of coseismic defor-mation is 5.5 km/s,close to the velocity of surface wave in granite.The logarithms of maximum amplitude of co-seismic deformation and epicentral distance have remarkable linear relationship with magnitude.The greater themagnitude and the closer the epicentral distance are,the bigger the maximum amplitude of coseismic deformationon non-causative fault will be.Relative to the epicentral distance,the magnitude is the most important factor to theduration of coseismic vertical deformation on the non-causative fault.Stronger earthquake causes longer vibrationduration of coseismic deformation.The experiential equation of co-seismic deformation faults obtained by thiswork is significant on the coseismic deformation research. 相似文献
3.
Uplift of a broad area centered ~6 km west of the summit of South Sister volcano started in September 1997 (onset estimated
from model discussed in this paper) and was continuing when surveyed in August 2006. Surface displacements were measured whenever
possible since August 1992 with satellite radar interferometry (InSAR), annually since August 2001 with GPS and leveling surveys,
and with continuous GPS since May 2001. The average maximum displacement rate from InSAR decreased from 3–5 cm/yr during 1998–2001
to ~1.4 cm/yr during 2004–2006. The other datasets show a similar pattern, i.e., surface uplift and extension rates decreased
over time but deformation continued through August 2006. Our best-fit model to the deformation data is a vertical, prolate,
spheroidal point-pressure source located 4.9–5.4 km below the surface. The source inflation rate decreased exponentially during
2001–2006 with a 1/e decay time of 5.3 ± 1.1 years. The net increase in source volume from September 1997 to August 2006 was 36.5–41.9 x 106 m3. A swarm of ~300 small (M
max = 1.9) earthquakes occurred beneath the deforming area in March 2004; no other unusual seismicity has been noted. Similar
deformation episodes in the past probably would have gone unnoticed if, as we suspect, most are small intrusions that do not
culminate in eruptions. 相似文献
4.
Characteristics of coseismic water level changes at Tangshan well for the Wenchuan MS8.0 earthquake and its larger aftershocks 
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下载免费PDF全文 Baojun Yin Li Ma Huizhong Chen Jianping Huang Chaojun Zhang Wuxing Wang 《地震科学（英文版）》2009,22(2):149-157
Coseismic water level changes which may have been induced by the Wenchuan MS8.0 earthquake and its 15 larger aftershocks (MS≥?5.4) have been observed at Tangshan well. We analyze the correlation between coseismic parameters (maximum amplitude, duration, coseismic step and the time when the coseismic reach its maximum amplitude) and earthquake parameters (magnitude, well-epicenter distance and depth), and then compare the time when the coseismic oscillation reaches its maximum amplitude with the seismogram from Douhe seismic station which is about 16.3 km away from Tangshan well. The analysis indicates that magnitude is the main factor influencing the induced coseismic water level changes, and that the well-epicenter distance and depth have less influence. MS magnitude has the strongest correlation with the coseismic water level changes comparing to MW and ML magnitudes. There exists strong correlation between the maximum amplitude, step size and the oscillation duration. The water level oscillation and step are both caused by dynamic strain sourcing from seismic waves. Most of the times when the oscillations reach their maximum amplitudes are between S and Rayleigh waves. The coseismic water level changes are due to the co-effect of seismic waves and hydro-geological environments. 相似文献
5.
The postseismic vertical deformation rates of the 1990 Gonghe M
S=7.0 earthquake appears to have decreased exponentially. Based on Okada’s coseismic surface displacement solution caused by
a uniform fault slip in an elastic homogeneous half space, we derived its postseismic surface displacement by using a single-layer
standard linear solid model, and further derived a simplified formula for determining the effective relaxation time and viscosity
of the earth, which is independent of the dislocation parameters of the causative fault. From the postseismic vertical deformation
of the 1990 Gonghe earthquake, we inferred that the effective relaxation time defined by τ=η/μ is 2.6 years, and the effective viscosity η is about 1018 Pa · s.
This work was supported by Chinese Joint Seismological Science Foundation under the grants 92088 and 196098. 相似文献
6.
7.
The preliminary research results of vertical deformation dislocation model of GongheM
S
=6.9 earthquake show that, the causative structure is a hidden fault with strike N60°W, dipping S47°W, which lies near the
current subsidence center of Gonghe basin. The rupture length and width are 30km and 14km, the upper and lower bound depth
of the fault in width direction are 3km and 17km respectively. The maximum coseismic and preseismic vertical deformation of
GongheM
S
=6.9 earthquake are 247mm and about 100mm. The reasons why there existed rapid postseismic uplift are also given a tentative
discussion.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 289–295, 1993. 相似文献
8.
V. F. Pisarenko A. Sornette D. Sornette M. V. Rodkin 《Pure and Applied Geophysics》2008,165(5):847-888
We develop a new method for the statistical estimation of the tail of the distribution of earthquake sizes recorded in the
Harvard catalog of seismic moments converted to m
W
-magnitudes (1977–2004 and 1977–2006). For this, we suggest a new parametric model for the distribution of main-shock magnitudes,
which is composed of two branches, the pure Gutenberg-Richter distribution up to an upper magnitude threshold m
1, followed by another branch with a maximum upper magnitude bound M
max, which we refer to as the two-branch model. We find that the number of main events in the catalog (N = 3975 for 1977–2004 and N = 4193 for 1977–2006) is insufficient for a direct estimation of the parameters of this model, due to the inherent instability
of the estimation problem. This problem is likely to be the same for any other two-branch model. This inherent limitation
can be explained by the fact that only a small fraction of the empirical data populates the second branch. We then show that
using the set of maximum magnitudes (the set of T-maxima) in windows of duration T days provides a significant improvement, in particular (i) by minimizing the negative impact of time-clustering of foreshock/main
shock/aftershock sequences in the estimation of the tail of magnitude distribution, and (ii) by providing via a simulation
method reliable estimates of the biases in the Moment estimation procedure (which turns out to be more efficient than the
Maximum Likelihood estimation). We propose a method for the determination of the optimal choice of the T value minimizing the mean-squares-error of the estimation of the form parameter of the GEV distribution approximating the
sample distribution of T-maxima, which yields T
optimal = 500 days. We have estimated the following quantiles of the distribution of T-maxima for the whole period 1977–2006: Q
16%(M
max) = 9.3, Q
50%(M
max) = 9.7 and Q
84%(M
max) = 10.3. Finally, we suggest two more stable statistical characteristics of the tail of the distribution of earthquake magnitudes:
The quantile Q
T
(q) of a high probability level q for the T-maxima, and the probability of exceedance of a high threshold magnitude ρ
T
(m*) = P{m
k
≥ m*}. We obtained the following sample estimates for the global Harvard catalog and The comparison between our estimates for the two periods 1977–2004 and 1977–2006, where the latter period included the great
Sumatra earthquake 24.12.2004, m
W
= 9.0 confirms the instability of the estimation of the parameter M
max and the stability of Q
T
(q) and ρ
T
(m*) = P{m
k
≥ m*}. 相似文献
9.
The Akto M_S6. 7 earthquake occurred near the western end of the Muji fault basin in the top of the Pamir syntaxis. The main shock of this earthquake is complicated and the focal mechanism solutions based on the seismic wave inversions are different. Based on the Sentinel-1 SAR data,the coseismal deformation field of the earthquake is obtained by In SAR technique. Based on the elastic half-space dislocation model,the geometrical parameters and the slip distribution model are determined by nonlinear and linear inversion algorithms. The results show that the distributed slip model can well explain the coseismic deformation field. The earthquake includes at least two rupture events,which are located at 7 km(74. 11°E,39. 25°N)and 33 km(74. 49°E,39. 16°N)east from the epicenter according to the CENC. The deformation field caused by the earthquake shows a symmetry distribution,with the maximum LOS deformation of 20 cm. The main seismic slip is concentrated in the 0-20 km depth,and the maximum slip is 0. 84 m. The seismic fault is the Muji fault,and this earthquake indicates that the northeastward push of the Indian plate is enhanced. 相似文献
10.
The complete records of geoelectric resistivity before two earthquakes were analyzed, including 16 stations within 240 km
around the Tangshan earthquake and 2 stations within 50–60 km from theM6.1 Datong earthquake. By eliminating various disturbances in the records and realizing the precursory anomalies to be reliable,
the authors studied the distribution of the geoelectric precursor field, which proves to be physically related to the earthquake
source stress field. Comparision of the sign distribution of coseismic resistivity changes with the solution of earthquake
source mechanism indicates that, the coseismic resistivity changes are of opposite sign but similar spatial distribution with
respect to the corresponding resistivity precursor changes. Therefore, from the resistivity observations we are of the opinion
that the Tangshan earthquake is an elastic rebound process. A virtual dislocation model of geoelectric precursor for the Tangshan
earthquake is proposed, in which the geoelectric precursors are supposed to be caused by the strain accumulation due to a
virtual dislocation, which is opposite in sign to the actual slip taking place at the earthquake occurrence. Taking into account
of the non-linear characteristics of the amplification factorK=(Δρ/ρ)/ɛ in a range of 10−7–10−5 strain changes, the theoretical distribution of geoelectric precursors for the Tangshan earthquake was calculated based on
the theory of fracture mechanics and reasonably selected dislocation parameters. The results show that the semi-quantitative
theoretical values are in good agreement with the observed, suggesting that the virtual dislocation model of the geoelectric
precursor is appropriate to the Tangshan earthquake.
Contribution No. 96A0023, Institute of Geophysics, SSB, China.
This work was supported by the National Natural Science Foundation of China and the Science and Technology Department of SSB. 相似文献
11.
Vladimir Sokolov Takashi Furumura Friedemann Wenzel 《Bulletin of Earthquake Engineering》2010,8(4):767-786
The estimation of strength of shaking at a site from the initial P-wave portion of ground motion is the key problems for shortening
the alert time of the earthquake Early Warning (EEW). The most of the techniques proposed for the purpose utilize (a) ground
motion models based on the estimated magnitude and hypocentral distance, or (b) the interim proxies, such as initial vertical
displacement P
d
. We suggest the instrumental Japan Meteorological Agency (JMA) intensity (JMAI) as a characteristic for fast estimation of damage potential in the EEW systems. We investigated the scaling relations between
JMAI measured using the whole earthquake recordings (overall intensity) and using particular time intervals of various duration
(2.0–8.0 s) starting from the P-wave arrival (preliminary intensity). The dataset included 3,660 records (K-NET and the KiK-net
networks) from 55 events (M
W 4.1–7.4) occurred in 1999–2008 in Japan. We showed that the time interval of 4–5 s from the P-wave arrival can be used for
reliable estimations of the overall intensity with the average standard error of about 0.5 JMA units. The uncertainty in the
prediction may be reduced by consideration of local site conditions or by development of the station-specific models. 相似文献
12.
The vesiculation of a peralkaline rhyolite melt (initially containing ∼0.14 wt.% H2O) has been investigated at temperatures above the rheological glass transition (T
g≈530 °C) by (a) in situ optical observation of individual bubble growth or dissolution and (b) dilatometric measurements
of the volume expansion due to vesiculation. The activation energy of the timescale for bubble growth equals the activation
energy of viscous flow at relatively low temperatures (650–790 °C), but decreases and tends towards the value for water diffusion
at high temperatures (790–925 °C). The time dependence of volume expansion follows the Avrami equation
ΔV (t)∼{1–exp [–(t/τav)
n
]}
with the exponent n=2–2.5. The induction time of nucleation and the characteristic timescale (τav) in the Avrami equation have the same activation energy, again equal to the activation energy of viscous flow, which means
that in viscous melts (Peclet number <1) the vesiculation (volume expansion), the bubble growth process, and, possibly, the nucleation of vesicles, are
controlled by the relaxation of viscous stresses. One of the potential volcanological consequences of such behavior is the
existence of a significant time lag between the attainment of a super-saturated state in volatile-bearing rhyolitic magmas
and the onset of their expansion.
Received: March 20, 1995 / Accepted: October 24, 1995 相似文献
13.
Directivity effects are a characteristic of seismic source finiteness and are a consequence of the rupture spread in preferential
directions. These effects are manifested through seismic spectral deviations as a function of the observation location. The
directivity by Doppler effect method permits estimation of the directions and rupture velocities, beginning from the duration
of common pulses, which are identified in waveforms or relative source time functions. The general model of directivity that
supports the method presented here is a Doppler analysis based on a kinematic source model of rupture (Haskell, Bull Seismol
Soc Am 54:1811–1841, 1964) and a structural medium with spherical symmetry. To evaluate its performance, we subjected the method to a series of tests
with synthetic data obtained from ten typical seismic ruptures. The experimental conditions studied correspond with scenarios
of simple and complex, unilaterally and bilaterally extended ruptures with different mechanisms and datasets with different
levels of azimuthal coverage. The obtained results generally agree with the expected values. We also present four real case
studies, applying the method to the following earthquakes: Arequipa, Peru (M
w = 8.4, June 23, 2001); Denali, AK, USA (M
w = 7.8; November 3, 2002); Zemmouri–Boumerdes, Algeria (M
w = 6.8, May 21, 2003); and Sumatra, Indonesia (M
w = 9.3, December 26, 2004). The results obtained from the dataset of the four earthquakes agreed, in general, with the values
presented by other authors using different methods and data. 相似文献
14.
Samir Belabbès Mustapha Meghraoui Ziyadin Çakir Youcef Bouhadad 《Journal of Seismology》2009,13(4):421-432
We study the surface deformation associated with the 22 December 1999 earthquake, a moderate sized but damaging event at Ain
Temouchent (northwestern Algeria) using Interferometric Satellite Aperture Radar images (InSAR). The mainshock focal mechanism
solution indicates reverse faulting with a NE–SW trending rupture comparable to other major seismic events of this section
of the Africa–Eurasia plate boundary. Previously, the earthquake fault parameters were, however, poorly known because no aftershocks
were precisely determined and no coseismic surface ruptures were observed in the field. Using a pair of ERS data with small
baseline and short temporal separation in the ascending orbit we obtained an interferogram that shows the coseismic surface
displacement field despite poor coherence. The interferogram measures four fringes and displays an ellipse-shaped lobe with
∼11 cm peak line-of-sight displacement. The elastic modeling using a boundary element method (Poly3Dinv) indicate coseismic
slip reaching up to 1 m at 5 km depth on the N 57° E trending, dipping 32° NW Tafna thrust fault. The geodetic estimate of
seismic moment is 4.7 × 1017 N m. (Mw 5.7) in is good agreement with seismological results. The elliptical shape of the surface displacement field coincides
with the NE–SW trending Berdani fault-related fold. The consistency between the geological observations and InSAR solution
shed light on the precise earthquake location and related Tafna fault parameters. 相似文献
15.
Bubble growth controlled by mass transfer of water from hydrated rhyolitic melts at high pressures and temperatures was studied
experimentally and simulated numerically. Rhyolitic melts were hydrated at 150 MPa, 780–850 °C to uniform water content of
5.5–5.3 wt%. The pressure was then dropped and held constant at 15–145 MPa. Upon the drop bubbles nucleated and were allowed
to grow for various periods of time before final, rapid quenching of the samples. The size and number density of bubbles in
the quenched glasses were recorded. Where number densities were low and run duration short, bubble sizes were in accord with
the growth model of Scriven (1959) for solitary bubbles. However, most results did not fit this simple model because of interaction
between neighboring bubbles. Hence, the growth model of Proussevitch et al. (1993), which accounts for finite separation between
bubbles, was further developed and used to simulate bubble growth.
The good agreement between experimental data, numerical simulation, and analytical solutions enables accurate and reliable
examination of bubble growth from a limited volume of supersaturated melt. At modest supersaturations bubble growth in hydrated
silicic melts (3–6 wt% water, viscosity 104–106 Pa·s) is diffusion controlled. Water diffusion is fast enough to maintain steady-state concentration gradient in the melt.
Viscous resistance is important only at the very early stage of growth (t<1 s). Under the above conditions growth is nearly
parabolic, R2=2Dtρm(C0–Cf)/ρg until the bubble approaches its final size. In melts with low water content, viscosity is higher and maintains pressure gradients
in the melt. Growth may be delayed for longer times, comparable to time scales of melt ascent during eruptions. At high levels
of supersaturation, advection of hydrated melt towards the growing bubble becomes significant.
Our results indicate that equilibrium degassing is a good approximation for modeling vesiculation in melts with high water
concentrations (C0>3 wt%) in the region above the nucleation level. When the melt accelerates and water content decreases, equilibrium can no
longer be maintained between bubbles and melt. Supersaturation develops in melt pockets away from bubbles and new bubbles
may nucleate. Further acceleration and increase in viscosity cause buildup of internal pressure in the bubbles and may eventually
lead to fragmentation of the melt.
Received: 19 June 1995 / Accepted: 27 December 1995 相似文献
16.
U. Yalçın Kalyoncuoglu 《Journal of Seismology》2007,11(2):131-148
In this study, the spatial distributions of seismicity and seismic hazard were assessed for Turkey and its surrounding area.
For this purpose, earthquakes that occurred between 1964 and 2004 with magnitudes of M ≥ 4 were used in the region (30–42°N and 20–45°E). For the estimation of seismicity parameters and its mapping, Turkey and
surrounding area are divided into 1,275 circular subregions. The b-value from the Gutenberg–Richter frequency–magnitude distributions is calculated by the classic way and the new alternative
method both using the least-squares approach. The a-value in the Gutenberg–Richter frequency–magnitude distributions is taken as a constant value in the new alternative method.
The b-values calculated by the new method were mapped. These results obtained from both methods are compared. The b-value shows different distributions along Turkey for both techniques. The b-values map prepared with new technique presents a better consistency with regional tectonics, earthquake activities, and
epicenter distributions. Finally, the return period and occurrence hazard probability of M ≥ 6.5 earthquakes in 75 years were calculated by using the Poisson model for both techniques. The return period and occurrence
hazard probability maps determined from both techniques showed a better consistency with each other. Moreover, maps of the
occurrence hazard probability and return period showed better consistency with the b-parameter seismicity maps calculated from the new method. The occurrence hazard probability and return period of M ≥ 6.5 earthquakes were calculated as 90–99% and 5–10 years, respectively, from the Poisson model in the western part of the
studying region. 相似文献
17.
Bin Zhao Wei Wang Shaomin Yang Maolei Peng Xuejun Qiao Ruilin Du Zhaosheng Nie 《Journal of Seismology》2012,16(2):305-313
This study estimates the far field coseismic deformation of China and its surrounding areas caused by the Mw9.0 Tohoku earthquake
of Japan using continuous GPS (cGPS) data and final orbits released by International GNSS Service (IGS). Based on these data,
we feature the coseismic offsets of several plates affected by the event. Static far field coseismic offsets greater than
2 mm are detected in a wide area of China, which extends as far as about 3,000 km off the epicenter, consisting of that of
the 2010 Maule, Chile earthquake. In northeast China, displacements up to 32.7 mm toward southeast are observed; meanwhile,
offsets in North China reach about 5–11 mm toward east. Coseismic jumps of about 2–5 mm are measured in South China toward
southeast. The southwest extrusion of the Philippine Sea plate is verified by GPS slip vectors, showing that the Philippine
Sea plate is decoupled from the Pacific plate by the earthquake. We also infer that the Amurian plate and the Okhotsk plate
couple well according to relatively continuous GPS offsets in these plates. Furthermore, the dense far field cGPS offsets
due to the Tohoku event hopefully provide opportunities to model the coseismic slip distribution. 相似文献
18.
运用Sentinel-1A卫星数据和D-InSAR技术,获取2021-05-21云南漾濞M_S6.4地震的同震形变场。结果显示,漾濞地震同震形变场长轴近NW展布升降轨形变场符号相反,视线向最大沉降量和抬升量为0.1 m。InSAR同震形变场反演的滑动分布主要集中在沿走向2～12 km,倾向1～9 km的范围内,最大滑动量0.35 m,发震断层长9.8 km、宽4 km,滑动量主要集中在地下3～6 km范围内,滑动角-146.7°。同震位移场及滑动分布模型反映本次地震为发震断层的右旋走滑事件,地震破裂未达到地表。断层模型反演结果显示,矩震级为M_W6.1,发震断层以北西走向右旋走滑运动为主,初步认为本次M_W6.1地震发震断裂可能是一条NW向的维西—乔后断裂西侧的隐伏次生断裂。 相似文献
19.
Youxue Zhang 《Bulletin of Volcanology》1998,59(4):281-290
Simulated gas-driven eruptions using CO2–water-polymer systems are reported. Eruptions are initiated by rapidly decompressing CO2–saturated water containing up to 1.0 wt.% CO2. Both cylindrical test cells and a flask test cell were used to examine the effect of magma chamber/conduit geometry on eruption
dynamics. Bubble-growth kinetics are examined quantitatively in experiments using cylindrical test cells. Uninhibited bubble
growth can be roughly expressed as dr/dt≈λD(β-1)/(γt
1/3) for a CO2–water-polymer system at 0–22 °C and with viscosities up to 5 Pa·s, where r is the radius of bubbles, λ and D are the Ostwald solubility coefficient and diffusivity of the gas in the liquid, β is the degree of saturation (decompression
ratio), and γ characterizes how the boundary layer thickness increases with time and is roughly 1.0×10–5 m/s1/3 in this system. Unlike the radius of cylindrical test cells, which does not affect the eruption threshold and dynamics, the
shape of the test cells (flask vs cylindrical) affects the dynamics but not the threshold of eruptions. For cylindrical test
cells, the front motion is characterized by constant acceleration with both Δh (the height increase) and ΔV (the volume increase) being proportional to t
2; for the flask test cell, however, neither Δh nor ΔV is proportional to t
2 as the conduit radius varies. Test-cell geometry also affects foam stability. In the flask test cell, as it moves from the
wider base chamber into the narrower conduit, the bubbly flow becomes fragmented, affecting the eruption dynamics. The fragmentation
may be caused by a sudden increase in acceleration induced by conduit-shape change, or by the presence of obstacles to the
bubbly flow. This result may help explain the range in vesicularities of pumice and reticulite.
Received: 16 May 1997 / Accepted: 11 October 1997 相似文献
20.
The seismic waves excited by the M
w
7.6 Olyutorskii earthquake that occurred on April 20, 2006 in the Koryak Upland gave rise to water-level changes in five
wells situated in continental areas of Kamchatka at hypocentral distances of 750–1150 km. We describe the effects due to seismic
waves, as well as the water-level anomalies for February–April 2006 before the earthquake. We used an original technique for
the processing of water-level records based on the study of barometric and tidal water-level responses in order to estimate
the volume strain in water-saturated rocks during synchronous level variations at two wells. We discuss possible mechanisms
for producing anomalous water-level changes due to elastic deformation of monitored groundwater reservoirs and to crack dilatancy
in the water-saturated rocks. 相似文献