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1.
本文用WKBJ方法,计算了中国境内已知震源机制的六个地震————1973年7月14日西藏约基台错地震;1975年2月4日海城地震;1976年8月16日、1976年8月21日及1976年8月23日松潘地震和1976年11月15日宁河地震————的远震垂直向P波和PP波的理论地震图,并与观测波形进行对比,以检验计算方法。讨论了西藏地震的震源机制。 作者注意到,走滑型地震和倾滑型地震PP波与P波最大振幅的比值在一定的震中距范围内有不同的特征。为此,计算了走滑型和倾滑型地震在破裂方位角为330,240和0,震源深度为8km,17km和24km,台站方主角为310时,震中距由40到80间的P波与PP波理论地震图。给出了PP波与P波最大振幅比(APP/AP)随震中距而变化的曲线。讨论了用(APP/AP)值对地震震源机制类型给出粗略的估计的可能性。此项工作有助于确定一些资料不全,例如本世纪30年代到60年代间中国地震的震源机制类型。 相似文献
2.
The source parameters of the Bohai Sea earthquake, July 18, 1969 and Yongshan, Yunnan earthquake, May 11, 1974 were determined
by full — wave theory synthetic seismograms of teleseismic P waves. P+pP+sP wereform were calculated with WKBJ approximation
and real integral paths. One — dimensional unilateral, finite propagation source was also considered. By trail — and — error
in comparing the theoretical seismograms with the observational ones of WWSSN stations, the source parameters were obtained
as follow: for Bohai earthquake, φ=195°, δ=85°, λ=65°,M
o=0.9×1019Nm,L=59.9km.V
R=3.5km/s, ∧
R
=160°; for Yongshan earthquake, φ=240°, δ=80°, ∧=150°,M
o=1.3×1018Nm,L=48.8km,V
R=3km/s, ∧
R
=−10°, where φ is strike, δ dip angle, λ slip angle,M
o seismic moment,L rupture length,V
R rupture propagation speed. As III type fractures the faulting propagated along the fault planes, and ∧
R
is the angle from the strike to the propagation direction. Yongshan earthquake showed complexity in its focal process, having
four sub—ruptures during the first 60 seconds.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 1–8, 1991. 相似文献
3.
Ya. B. Radziminovich A. I. Seredkina V. I. Melnikova N. A. Gilyova 《Seismic Instruments》2017,53(4):323-332
The paper considers the Argun earthquake of July 22, 2011 (M w = 4.5), which occurred in the Argun River valley in a low-seismicity territory in China. The focal parameters of the earthquake (depth of the hypocenter, moment magnitude, scalar seismic moment, and focal mechanism) were determined by calculating the seismic moment tensor from the amplitude spectra of surface waves and the data on the signs of the first arrivals of body waves at regional stations. The solution of the focal mechanism makes it possible to assume a relationship between the earthquake focus and a fault with a northeastern strike bordering the southeastern side of the Argun Basin (in Chinese territory). The Argun earthquake was felt in Russia with an intensity of II–III to V at the epicentral distances up to 255 km. The intensity of shaking did not exceed values suggested by new GSZ-2012 and GSZ-2014 seismic zoning maps of Russian territory. Nevertheless, the question on the possible occurrence of stronger earthquakes in the studied region remains open. 相似文献
4.
通过对中国数字地震仪台网(CDSN)11个台1993—2012年间30个极远震记录的分析,识别出了PKP波入射到内外核界面(ICB)上的衍射波PKPdif波。PKPdif波在震中距120°左右时出现在PKIKP波之前,在震中距150°以后出现在PKIKP波之后,是一个长周期波。为了解释PKPdif波超前于PKIKP波的原因,设想在距地面约5 156.1～5 372.2 km的深度,即内外核界面下有可能存在一个PKIKP波的低速层(厚度约216.1 km)。该设想符合Jeffreys速度模型,给出的PKPdif波在震中距119.4°～176.1°间的走时表填补了目前使用的《IASPEI1991地震波走时表》的空白。讨论PKPdif波的运动学特征有助于对内外核界面物理性质的认识,有助于提高分析震相的水平和积累震相分析经验。 相似文献
5.
6.
Features and physical process of the dynamic evolution pattern of ground resistivity precursor front
ＩｎｔｒｏｄｕｃｔｉｏｎＳｉｎｃｅｔｈｅ１９６０′ｓ,ｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｍｏｄｅｒｎｓｃｉｅｎｃｅａｎｄｔｅｃｈｎｏｌｏｇｙｈａｓｇｒａｄｕａｌｙｍａｄｅｉｔｐｏｓｉｂｌｅｔｏｐｒｅｄｉｃｔｅａｒｔｈｑｕａｋｅｓａｎｄｈａｓｐｒｏｍｏｔ... 相似文献
7.
Introduction The January 10, 1998 Zhangbei-Shangyi, Hebei Province, earthquake has been the third large event of magnitude 6.0 and greater since the 1976 great Tangshan earthquake of magnitude 7.8 in the northern China (33皛42癗, 110皛124癊). Before this event, there were only two events of magnitude 6.0 and greater occurred in or around the Tangshan area since 1976: the M=6.9 Ninghe, Tianjin, earthquake of November 15, 1976 and the M=6.2 Hangu, Tianjin, earthquake of May 12, 1977. The … 相似文献
8.
9.
The seismogenic fault and the dynamic mechanism of the Ning’er, Yunnan Province MS6.4 earthquake of June 3, 2007 are studied on the basis of the observation data of the surface fissures, sand blow and water eruption, land-slide and collapse associated with the earthquake, incorporating with the data of geologic structures, focal mecha-nism solutions and aftershock distribution for the earthquake area. The observation of the surface fissures reveals that the Banhai segment of the NW-trending Ning’er fault is dominated by right-lateral strike-slip, while the NNE-trending fault is dominated by left-lateral strike-slip. The seismo-geologic hazards are concentrated mainly within a 330°-extending zone of 13.5 km in length and 4 km in width. The major axis of the isoseismal is also oriented in 330° direction, and the major axis of the seismic intensity VIII area is 13.5 km long. The focal mechanism solutions indicate that the NW-trending nodal plane of the Ning’er MS6.4 earthquake is dominated by right-lateral slip, while the NE-trending nodal plane is dominated by left-lateral slip. The preferred distribution orientation of the aftershocks of MS≥2 is 330°, and the focal depths are within the range of 3~12 km, predominantly within 3~10 km. The distribution of the aftershocks is consistent with the distribution zone of the seismo-geologic hazards. All the above-mentioned data indicate that the Banhai segment of the Ning’er fault is the seismogenic fault of this earthquake. Moreover, the driving force of the Ning’er earthquake is discussed in the light of the active block theory. It is believed that the northward pushing of the Indian plate has caused the eastward slipping of the Qinghai-Tibetan Plateau, which has been transformed into the southeastern-southernward squeezing of the southwest Yunnan region. As a result, the NW-trending faults in the vicinity of the Ning’er area are dominated by right-lateral strike-slip, while the NE-trending faults are dominated by left-lateral strike-slip. This tectonic 相似文献
10.
In this paper changes in focal mechanisms) parameters of wave spectra, and stress drops for the Ms=5.0 forcshock and Ms=6.0 mainshock in February 2001 in Yajiang County, Sichuan, and seismicity in cpiccntral region are studied. Comparison of focal mechanisms for the Yajiang earthquakes with distribution patterns of aftcrshocks, the nodal plane Ⅰ, striking in the direction of NEN, of the Yajiang M=5.0 event is chosen as the faulting plane, the nodal plane Ⅱ, striking in the direction of WNW, of the M=6.0 event as the faulting plane. The strikes of the two faulting planes are nearly perpendicular to each other. The level of stress drops in the cpicentral region before the occurrence of the M=6.0 earthquake increases, which is consistent with increase of seismicity in the epicentral region. The rate decay of the Yajiang earthquake sequence, changes in wave spectra for foreshocks and aftershocks,and focal mechanisms are complex. 相似文献
11.
Fracture characteristics of the 1997 Jiashi, Xinjiang, China, earthquake swarm inferred from source spectra 总被引：2，自引：0，他引：2
SHI-YONG ZHOU 《地震学报(英文版)》2000,13(2):125-135
Broadband P and S waves source spectra of 12 MS5.0 earthquakes of the 1997 Jiashi, Xinjiang, China, earthquake swarm recorded at 13 GDSN stations have been analyzed. Rupture size and static stress drop of these earthquakes have been estimated through measuring the corner frequency of the source spectra. Direction of rupture propagation of the earthquake faulting has also been inferred from the azimuthal variation of the corner frequency. The main results are as follows: ①The rupture size of MS6.0 strong earthquakes is in the range of 10～20 km, while that of MS=5.0～5.5 earthquakes is 6～10 km.② The static stress drop of the swarm earthquakes is rather low, being of the order of 0.1 MPa. This implies that the deformation release rate in the source region may be low. ③ Stress drop of the earthquakes appears to be proportional to their seismic moment, and also to be dependent on their focal mechanism. The stress drop of normal faulting earthquakes is usually lower than that of strike-slip type earthquakes. ④ For each MS6.0 earthquake there exists an apparent azimuthal variation of the corner frequencies. Azimuthally variation pattern of corner frequencies of different earthquakes shows that the source rupture pattern of the Jiashi earthquake swarm is complex and no uniform rupture expanding direction exists. 相似文献
12.
William Menke Hannah Abend Dalia Bach Kori Newman Vadim Levin 《Surveys in Geophysics》2006,27(6):603-613
The December 26, 2004 Sumatra–Andaman Island earthquake, which ruptured the Sunda Trench subduction zone, is one of the three largest earthquakes to occur since global monitoring began in the 1890s. Its seismic moment was M
0 = 1.00 × 1023–1.15 × 1023 Nm, corresponding to a moment-magnitude of M
w
= 9.3. The rupture propagated from south to north, with the southerly part of fault rupturing at a speed of 2.8 km/s. Rupture propagation appears to have slowed in the northern section, possibly to ∼2.1 km/s, although published estimates have considerable scatter. The average slip is ∼5 m along a shallowly dipping (8°), N31°W striking thrust fault. The majority of slip and moment release appears to have been concentrated in the southern part of the rupture zone, where slip locally exceeded 30 m. Stress loading from this earthquake caused the section of the plate boundary immediately to the south to rupture in a second, somewhat smaller earthquake. This second earthquake occurred on March 28, 2005 and had a moment-magnitude of M
w
= 8.5. 相似文献
13.
Forensic seismology revisited 总被引：1，自引：0，他引：1
A. Douglas 《Surveys in Geophysics》2007,28(1):1-31
The first technical discussions, held in 1958, on methods of verifying compliance with a treaty banning nuclear explosions,
concluded that a monitoring system could be set up to detect and identify such explosions anywhere except underground: the
difficulty with underground explosions was that there would be some earthquakes that could not be distinguished from an explosion.
The development of adequate ways of discriminating between earthquakes and underground explosions proved to be difficult so
that only in 1996 was a Comprehensive Nuclear Test Ban Treaty (CTBT) finally negotiated. Some of the important improvements
in the detection and identification of underground tests—that is in forensic seismology—have been made by the UK through a
research group at the Atomic Weapons Establishment (AWE). The paper describes some of the advances made in identification
since 1958, particularly by the AWE Group, and the main features of the International Monitoring System (IMS), being set up
to verify the Test Ban.
Once the Treaty enters into force, then should a suspicious disturbance be detected the State under suspicion of testing will
have to demonstrate that the disturbance was not a test. If this cannot be done satisfactorily the Treaty has provisions for
on-site inspections (OSIs): for a suspicious seismic disturbance for example, an international team of inspectors will search
the area around the estimated epicentre of the disturbance for evidence that a nuclear test really took place.
Early observations made at epicentral distances out to 2,000 km from the Nevada Test Site showed that there is little to distinguish
explosion seismograms from those of nearby earthquakes: for both source types the short-period (SP: ∼1 Hz) seismograms are
complex showing multiple arrivals. At long range, say 3,000–10,000 km, loosely called teleseismic distances, the AWE Group
noted that SP P waves—the most widely and well-recorded waves from underground explosions—were in contrast simple, comprising
one or two cycles of large amplitude followed by a low-amplitude coda. Earthquake signals on the other hand were often complex
with numerous arrivals of similar amplitude spread over 35 s or more. It therefore appeared that earthquakes could be recognised
on complexity. Later however, complex explosion signals were observed which reduced the apparent effectiveness of complexity
as a criterion for identifying earthquakes. Nevertheless, the AWE Group concluded that for many paths to teleseismic distances,
Earth is transparent for P signals and this provides a window through which source differences will be most clearly seen.
Much of the research by the Group has focused on understanding the influence of source type on P seismograms recorded at teleseismic
distances. Consequently the paper concentrates on teleseismic methods of distinguishing between explosions and earthquakes.
One of the most robust criteria for discriminating between earthquakes and explosions is the m
b : M
s criterion which compares the amplitudes of the SP P waves as measured by the body-wave magnitude m
b, and the long-period (LP: ∼0.05 Hz) Rayleigh-wave amplitude as measured by the surface-wave magnitude M
s; the P and Rayleigh waves being the main wave types used in forensic seismology. For a given M
s, the m
b for explosions is larger than for most earthquakes. The criterion is difficult to apply however, at low magnitude (say m
b < 4.5) and there are exceptions—earthquakes that look like explosions.
A difficulty with identification criteria developed in the early days of forensic seismology was that they were in the main
empirical—it was not known why they appeared to work and if there were test sites or earthquakes where they would fail. Consequently
the AWE Group in cooperation with the University of Cambridge used seismogram modelling to try and understand what controls
complexity of SP P seismograms, and to put the m
b : M
s criterion on a theoretical basis. The results of this work show that the m
b : M
s criterion is robust because several factors contribute to the separation of earthquakes and explosions. The principal reason
for the separation however, is that for many orientations of the earthquake source there is at least one P nodal plane in
the teleseismic window and this biases m
b low. Only for earthquakes with near 45° dip-slip mechanisms where the antinode of P is in the source window is the m
b:M
s criterion predicted to fail. The results from modelling are consistent with observation—in particular there are earthquakes,
“anomalous events”, which look explosion-like on the m
b:M
s criterion, that turn out to have mechanisms close to 45° dip-slip. Fortunately the P seismograms from such earthquakes usually
show pP and sP, the reflections from the free surface of P and S waves radiated upwards. From the pP–P and sP–P times the
focal depth can be estimated. So far the estimated depth of the anomalous events have turned out to be ∼20 km, too deep to
be explosions.
Studies show that the observation that P seismograms are more complex than predicted by simple models can be explained on
the weak-signal hypothesis: the standard phases, direct P and the surface reflections, are weak because of amongst other things,
the effects of the radiation pattern or obstacles on the source-to-receiver path; other non-standard arrivals then appear
relatively large on the seismograms.
What has come out of the modelling of P seismograms is a criterion for recognising suspicious disturbances based on simplicity
rather than complexity. Simple P seismograms for earthquakes at depths of more than a few kilometres are likely to be radiated
only to stations that lie in a confined range of azimuths and distances. If then, simple seismograms are recorded over a wide
range of distances and particularly azimuths, it is unlikely the source is an earthquake at depth. It is possible to test
this using the relative amplitudes of direct P and later arrivals that might be surface reflections. The procedure is to use
only the simple P seismograms on the assumption that whereas the propagation through Earth may make a signal more complex
it is unlikely to make it simpler. From the amplitude of the coda of these seismograms, bounds can be placed on the size of
possible pP and sP. The relative-amplitude method is then used to search for orientations of the earthquake source that are
compatible with the observations. If no such orientations are found the source must be shallow so that any surface reflections
merge with direct P, and hence could be an explosion.
The IMS when completed will be a global network of 321 monitoring stations, including 170 seismological stations principally
to detect the seismic waves from earthquakes and underground explosions. The IMS will also have stations with hydrophones,
microbarographs and radionuclide detectors to detect explosions in the oceans and the atmosphere and any isotopes in the air
characteristic of a nuclear test. The Global Communications Infrastructure provides communications between the IMS stations
and the International Data Centre (IDC), Vienna, where the recordings from the monitoring stations is collected, collated,
and analysed. The IDC issues bulletins listing geophysical disturbances, to States Signatories to the CTBT.
The assessment of the disturbances to decide whether any are possible explosions, is a task for State Signatories. For each
Signatory to do a detailed analysis of all disturbances would be expensive and time consuming. Fortunately many disturbances
can be readily identified as earthquakes and removed from consideration—a process referred to as “event screening”. For example,
many earthquakes with epicentres over the oceans can be distinguished from underwater explosions, because an explosion signal
is of much higher frequency than that of earthquakes that occur below the ocean bed. Further, many earthquakes could clearly
be identified at the IDC on the m
b : M
s criterion, but there is a difficulty—how to set the decision line. The possibility has to be very small that an explosion
will be classed by mistake, as an earthquake. The decision line has therefore to be set conservatively, consequently with
routine application of current screening criteria, only about 50% of earthquakes can be positively identified as such.
Various methods have been proposed whereby a “determined violator” could avoid the provisions of a CTBT and carry out a test
that would be either undetected or detected but not identified as an explosion. The increase in complexity and cost of such
a test should discourage any State from attempting it. In addition, there is always the possibility of some stations detecting
the test, the test being identified as suspicious, and so subject to an OSI. With time as the IMS becomes more efficient and
effective it will act increasingly to deter anyone contemplating a clandestine test, from going ahead.
What has emerged is several robust criteria. The criteria include: location, which when combined with hydro-acoustic data
can identify earthquakes under the sea; m
b : M
s; and depth of focus. More detailed study is required of any remaining seismic disturbance that is regarded as suspicious:
for example, is close to a site where nuclear tests have been carried out in the past. Any disturbance that is shown to be
explosion-like, may be the subject of an OSI.
One surprise is how little plate tectonics has contributed to resolving problems in forensic seismology. Much of the evidence
for plate tectonics comes from seismological studies so it would be expected that the implications for Earth structure arising
from forensic seismology would be consistent with plate-tectonic models. So far the AWE Group have found little synergy between
plate tectonics and forensic seismology.
It is to be hoped that the large volume of seismological data of high quality now being collected by the IMS and the increasing
number of digital stations, will result in a revised Earth model that is consistent with the findings of forensic seismology,
so that a future review of progress will show that the forensic seismologist can draw on this model in attempting to interpret
apparently anomalous seismograms.
相似文献
| A. DouglasEmail: |
14.
Characteristics of recent tectonic stress field in Jiashi, Xinjiang and adjacent regions 总被引：1，自引：0，他引：1
崔效锋 《地震学报(英文版)》2006,19(4):370-379
Introduction The Pamirs region where Jiashi is located is one of the most active regions of continental plate dynamics in China. Frequent earthquakes here, especially several strong earthquakes oc- curred in 1997 and 2003, have provided excellent conditions for studying the tectonic stress field in this region and a large number of results (GAO and WEN, 2000; GAO et al, 2004; XU, 2001; ZHOU et al, 2001) have been obtained. Although different methods and data were used, under- standings … 相似文献
15.
Katsuyuki Abe 《Physics of the Earth and Planetary Interiors》1985,39(3):157-166
The large deep earthquake of January 21, 1906 is re-evaluated using old seismogram data and updated analysis techniques. From the P and pP-P time data the hypocentre parameters are determined as follows: origin time, 13h 49min 35s; latitude, 33.8°N; longitude, 137.5°E; depth, 340 km. The body-wave magnitude mB is re-evaluated from the amplitude and periods of P, PP and S waves. The average value of 7.4 is obtained. This value is the smallest among any values assigned previously to this shock, and it is denied that the earthquake is the world's largest deep shock in this century. The focal mechanism is estimated from the P-wave first motions and amplitude distribution of P and S waves. Synthetic body waves are used to constrain the mechanism and to determine the seismic moment. The mechanism solution suggests the down-dip compression typical of this region. A seismic moment of 1.5 × 1027 dyn · cm is obtained. This value and the re-evaluated value of mB are consistent with the moment-B relation obtained for other deep earthquakes. 相似文献
16.
Giuseppe Pasquale Raffaella De Matteis Annalisa Romeo Rosalba Maresca 《Journal of Seismology》2009,13(1):107-124
The goal of this study was to estimate the stress field acting in the Irpinia Region, an area of southern Italy that has been
struck in the past by destructive earthquakes and that is now characterized by low to moderate seismicity. The dataset are
records of 2,352 aftershocks following the last strong event: the 23 November 1980 earthquake (M 6.9). The earthquakes were
recorded at seven seismic stations, on average, and have been located using a three-dimensional (3D) P-wave velocity model
and a probabilistic, non-linear, global search technique. The use of a 3D velocity model yielded a more stable estimation
of take-off angles, a crucial parameter for focal mechanism computation. The earthquake focal mechanisms were computed from
the P-wave first-motion polarity data using the FPFIT algorithm. Fault plane solutions show mostly normal component faulting
(pure normal fault and normal fault with a strike-slip component). Only some fault plane solutions show strike-slip and reverse
faulting. The stress field is estimated using the method proposed by Michael (J Geophys Res 92:357–368, 1987a) by inverting selected focal mechanisms, and the results show that the Irpinia Region is subjected to a NE–SW extension with
horizontal σ
3 (plunge 0°, trend 230°) and subvertical σ
1 (plunge 80°, trend 320°), in agreement with the results derived from other stress indicators. 相似文献
17.
According to geological tectonics and seismic activites this paper devided North China (30°–45°N, 105°–130°E) into four areas.
We analyzed the North China earthquake catalogue from 1970 to 1986 (from 1965 to 1986 for Huabei, the North China, plain region)
and identified forty-two bursts of aftershock. Seven of them occurred in aftershock regions of strong earthquakes and seventeen
of them in the seismic swarm regions. The relation between strong earthquakes with the remaining eighteen bursts of aftershocks
has been studied and tested statistically in this paper. The result of statistical testing show that the random probabilityp of coincidence of bursts of aftershock with subsequent strong earthquakes is less than six percent. By Xu’sR scoring method the efficacy of predicting strong earthquake from bursts of aftershock is estimated greater than 39 percent.
Following the method proposed in the paper we analyzed the earthquake catalogue of China from 1987 to June, 1988. The results
show that there was only one burst of aftershock occurred on Jan. 6, 1988 withM=3.6 in Xiuyan of Northeast China. It implicates that a potential earthquake withM
S⩽5 might occur in one year afterwards in the region of Northeast China. Actually on Feb. 25, 1988 an earthquake withM
S=5.3 occurred in Zhangwu of Northeast China. Another example is Datong-Yanggao shock on October 18, 1989 which is a burst
of aftershock. Three hours after an expected shock withM =6.1 took place in the same area. Two examples above have been tested in practical prediction and this shows that bursts
of aftershocks are significant in predicting strong earthquakes.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 273–280, 1991.
Part of earthquake catalogue is from Jinbiao Chen, Peiyan Chen and Quanlin Li. 相似文献
18.
对不同震中距台站的记录采用入射角法、s PL-Pg等震相到时差,对辽宁地震台网记录采用单纯形法研究了辽阳灯塔5.1级地震的震源深度。结果表明,该地震震源深度应为14km,略大于目录给出的10km。利用四川松潘台、青海湟源台的远台记录也得到同样的结果。通过对辽宁1970年以来5.0级以上地震进行分析发现,辽宁地震的震源分布存在东西两侧偏深、中部偏浅、中部地区南浅北深的统计规律,灯塔地震震源深度符合该统计规律。 相似文献
19.
Using the Cut And Paste (CAP) method, we invert the focal mechanism of 38 moderate earthquakes (MS ≥ 3.0) recorded by Yunnan seismic network and analyze the corresponding focal mechanism consistency based on the minimum spatial rotation angle. Our results indicate that the MS 6.4 mainshock is induced by a lateral strike slip fault (with a rake angle of ～ ?165°) and a little normal-faulting component event along a nearly vertical plane (dipping angle～ 79° and strike ～138°). Combining our results with high resolution catalog, we argue that the seismogenic fault of this earthquake sequence is a secondary fault western to the major Weixi-Qiaohou-Weishan fault. The focal mechanism evolution can be divided into three periods. During the first period, the foreshock sequence, the focal mechanism consistency is the highest (KA<36°); during the second period which is shortly after the mainshock, the focal mechanism shows strong variation with KA ranging from 8° to 110°; during the third period, the seismicity becomes weak and the focal mechanism of the earthquakes becomes more consistent than the second period (18°<KA<73°). We suggest that the KA, to some extent, represents the coherence between local tectonic stress regime and the stress state of each individual earthquake. Furthermore, high focal mechanism consistency and high linearity of seismic distribution may serve as indicators for the identification of foreshock sequence. 相似文献
20.
Turkey was struck by two major events on August 17th and November 12th, 1999. Named Kocaeli (Mw=7.4) and Düzce (Mw=7.2) earthquakes, respectively, the two earthquakes provided the most extensive strong ground motion data set ever recorded in Turkey. The strong motion stations operated by the General Directorate of Disaster Affairs, the Kandilli Observatory and Earthquake Research Institute of Bogazici University and Istanbul Technical University have produced at least 27 strong motion records for the Kocaeli earthquake within 200 km of the fault. Kocaeli earthquake has generated six motions within 20 km of the fault adding significantly to the near-field database of ground motions for Mw>=7.0 strike–slip earthquakes. The paper discusses available strong motion data, studies their attenuation characteristics, analyses time domain, as well as spectral properties such as spectral accelerations with special emphasis on fault normal and fault parallel components and the elastic attenuation parameter, kappa. A simulation of the Kocaeli earthquake using code FINSIM is also presented. 相似文献