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1.
We utilized nuclear explosions from the Degelen Mountain sub-region of the Semipalatinsk Test Site (STS), Kazakhstan, to assess seismic location capability directly. Excellent ground truth information for these events was either known or was estimated from maps of the Degelen Mountain adit complex. Origin times were refined for events for which absolute origin time information was unknown using catalog arrival times, our ground truth location estimates, and a time baseline provided by fixing known origin times during a joint hypocenter determination (JHD). Precise arrival time picks were determined using a waveform cross-correlation process applied to the available digital data. These data were used in a JHD analysis. We found that very accurate locations were possible when high precision, waveform cross-correlation arrival times were combined with JHD. Relocation with our full digital data set resulted in a mean mislocation of 2 km and a mean 95% confidence ellipse (CE) area of 6.6 km2 (90% CE: 5.1 km2), however, only 5 of the 18 computed error ellipses actually covered the associated ground truth location estimate. To test a more realistic nuclear test monitoring scenario, we applied our JHD analysis to a set of seven events (one fixed) using data only from seismic stations within 40° epicentral distance. Relocation with these data resulted in a mean mislocation of 7.4 km, with four of the 95% error ellipses covering less than 570 km2 (90% CE: 438 km2), and the other two covering 1730 and 8869 km2 (90% CE: 1331 and 6822 km2). Location uncertainties calculated using JHD often underestimated the true error, but a circular region with a radius equal to the mislocation covered less than 1000 km2 for all events having more than three observations.  相似文献   

2.
Improving Regional Seismic Event Location in China   总被引：1，自引：0，他引：1  
—?In an effort to improve our ability to locate seismic events in China using only regional data, we have developed empirical propagation path corrections and applied such corrections using traditional location routines. Thus far, we have concentrated on corrections to observed P arrival times for crustal events using travel-time observations available from the USGS Earthquake Data Reports, the International Seismic Centre Bulletin, the preliminary International Data Center Reviewed Event Bulletin, and our own travel-time picks from regional data. Location ground truth for events used in this study ranges from 25?km for well-located teleseimic events, down to 2?km for nuclear explosions located using satellite imagery. We also use eight events for which depth is constrained using several waveform methods. We relocate events using the EvLoc algorithm from a region encompassing much of China (latitude 20°–55°N; longitude 65°–115°E). We observe that travel-time residuals exhibit a distance-dependent bias using IASPEI91 as our base model. To remedy this bias, we have developed a new 1-D model for China, which removes a significant portion of the distance bias. For individual stations having sufficient P-wave residual data, we produce a map of the regional travel-time residuals from all well-located teleseismic events. Residuals are used only if they are smaller than 10?s in absolute value and if the seismic event is located with accuracy better than 25?km. From the residual data, correction surfaces are constructed using modified Bayesian kriging. Modified Bayesian kriging offers us the advantage of providing well-behaved interpolants and their errors, but requires that we have adequate error estimates associated with the travel-time residuals from which they are constructed. For our P-wave residual error estimate, we use the sum of measurement and modeling errors, where measurement error is based on signal-to-noise ratios when available, and on the published catalog estimate otherwise. Our modeling error originates from the variance of travel-time residuals for our 1-D China model. We calculate propagation path correction surfaces for 74 stations in and around China, including six stations from the International Monitoring System. The statistical significance of each correction surface is evaluated using a cross-validation technique. We show relocation results for nuclear tests from the Balapan and Lop Nor test sites, and for earthquakes located using interferometric synthetic aperture radar. These examples show that the use of propagation path correction surfaces in regional relocations eliminates distance bias in the residual curves and significantly improves the accuracy and precision of seismic event locations.  相似文献   

3.
—?We test how well low-magnitude (m bLg 1.8 to 2.6), 25-ton chemical explosions at Balapan, Kazakhstan, can be located using IMS stations and standard earth models, relying on precisely determined relative arrival times of nearly similar, regional and teleseismic waveforms. Three 1997 Balapan explosions were recorded by a number of currently reporting and surrogate IMS stations. Three regional stations and two teleseismic arrays yielded consistent waveforms appropriate for relative picking. Master-event locations based on the AK135 model and ground-truth information from the first, shallowest and best-recorded explosion, fell under 1 km from known locations, for depths constrained to that of the master event. The resulting 90% confidence ellipses covered 12–13?km2 and contained the true locations; however, results for depth constrained to true depth were slightly less satisf actory. From predictions based on ground truth, we found a P g -coda phase at Makanchi, Kazakhstan to be misidentified and poorly modeled. After accounting for this, 90% ellipses shrank to 2–3?km2 and true-depth mislocation vectors became more consistent with confidence-ellipse orientations. These results suggest that a high level of precision could be provided by a tripartite array of calibration shots in cases where models are poorly known. We hope that the successful relocation of these small Balapan shots will support the role of calibration explosions in verification monitoring and special event studies, including on-site inspection.  相似文献   

4.
The epicentres of explosions at two test sites – Balapan (Shagan River), Former Soviet Union and Lop Nor, China – are estimated using the onset times of P from only three or four array stations at teleseismic distances. The epicentres of the explosions are known to within about 1 km from studies that make use of information from satellite imagery; these estimates are taken to be the true epicentres. With the true epicentres, differences between the true travel times and the times from travel-time tables are estimated. The differences include a component – path effects – that results in epicentre bias. Comparing our estimates using three or four stations with the true epicentres shows that with correction for path effects most of the epicentres are within 5 km of true and even without correction most estimated epicentres are within 10 km of true. The results confirm the conclusion of Evernden that if reading error in P times has a standard deviation of a few tenths of a second, reliable epicentres can be obtained given readings from only a few stations. This implies, what has been noted by others, that for epicentre estimation, better results can be obtained with a few well read P times from a constant network of the most reliable and sensitive stations, than by using uncritically all the available times. Even without correction for path effects none of the explosions (with times free from possible clock errors) falls outside a circular 1000 km2 region; 1000 km2 being the search area allowed for an on-site inspection under the Comprehensive Test Ban Treaty. The results suggest that rather than try and calibrate the whole of the International Monitoring System, being set up to verify the Test Ban, it would be better initially to concentrate on calibrating the few stations with the longest recording history and lowest detection thresholds.  相似文献   

5.
—?Seismic event locations based on regional 1-D velocity-depth sections can have bias errors caused by travel-time variations within different tectonic provinces and due to ray-paths crossing boundaries between tectonic provinces with different crustal and upper mantle velocity structures. Seismic event locations based on 3-D velocity models have the potential to overcome these limitations. This paper summarizes preliminary results for calibration of IMS for North America using 3-D velocity model. A 3-D modeling software was used to compute Source-Station Specific Corrections (SSSCs(3-D)) for Pn travel times utilizing 3-D crustal and upper mantle velocity model for the region. This research was performed within the framework of the United States/Russian Federation Joint Program of Seismic Calibration of the International Monitoring System (IMS) in Northern Eurasia and North America.¶An initial 3-D velocity model for North America was derived by combining and interpolating 1-D velocity-depth sections for different tectonic units. In areas where no information on 1-D velocity-depth sections was available, tectonic regionalization was used to extrapolate or interpolate. A Moho depth map was integrated. This approach combines the information obtained from refraction profiles with information derived from local and regional network data. The initial 3-D velocity model was tested against maps of Pn travel-time residuals for eight calibration explosions; corrections to the 3-D model were made to fit the observed residuals. Our goal was to find a 3-D crustal and upper mantle velocity model capable predicting Pn travel times with an accuracy of 1.0–1.5 seconds (r.m.s.).¶The 3-D velocity model for North America that gave the best fit to the observed travel times, was used to produce maps of SSSCs(3-D) for seismic stations. The computed SSSCs(3-D) vary approximately from +5 seconds to ?5 seconds for the western USA and the Pre-Cambrian platform, respectively. These SSSCs(3-D) along with estimated modeling and measurement errors were used to relocate, using regional data, an independent set of large chemical explosions (with known locations and origin times) detonated within various tectonic provinces of North America. Utilization of the 3-D velocity model through application of the computed SSSCs(3-D) resulted in a substantial improvement in seismic event location accuracy and in a significant decrease of error ellipse area for all events analyzed in comparison both with locations based on the IASPEI91 travel times and locations based on 1-D regional velocity models.  相似文献   

6.
Because ambient seismic noise provides estimated Greenos function (EGF) between two sites with high accuracy, Rayleigh wave propagation along the path connecting the two sites is well resolved. Therefore, earthquakes which are close to one seismic station can be well located with calibration extracting from EGF. We test two algorithms in locating the 1998 Zhangbei earthquake, one algorithm is waveform-based, and the other is traveltime-based. We first compute EGF between station ZHB (a station about 40 km away from the epicenter) and five IC/IRIS stations. With the waveform-based approach, we calculate 1D synthetic single-force Greenos functions between ZHB and other four stations, and obtain traveltime corrections by correlating synthetic Greenos functions with EGFs in period band of 10-30 s. Then we locate the earthquake by minimizing the differential travel times between observed earthquake waveform and the 1D synthetic earthquake waveforms computed with focal mechanism provided by Global CMT after traveltime correction from EGFs. This waveform-based approach yields a location which error is about 13 km away from the location observed with InSAR. With the traveltime-based approach, we begin with measuring group velocity from EGFs as well as group arrival time on observed earthquake waveforms, and then locate the earthquake by minimizing the difference between observed group arrival time and arrival time measured on EGFs. This traveltime-based approach yields accuracy of 3 km, Therefore it is feasible to achieve GT5 (ground truth location with accuracy 5 km) with ambient seismic noises. The less accuracy of the waveform-based approach was mainly caused by uncertainty of focal mechanism.  相似文献   

7.
We test the performance of high-frequency regional P/S discriminants to differentiate between earthquakes and explosions at test sites and over broad regions using a historical dataset of explosions recorded at the Borovoye Observatory in Kazakhstan. We compare these explosions to modern recordings of earthquakes at the same location. We then evaluate the separation of the two types of events using the raw measurements and those where the amplitudes are corrected for 1-D and 2-D attenuation structure. We find that high-frequency P/S amplitudes can reliably identify earthquakes and explosions, and that the discriminant is applicable over broad regions as long as propagation effects are properly accounted for. Lateral attenuation corrections provide the largest improvement in the 2–4 Hz band, the use of which may successfully enable the identification of smaller, distant events that have lower signal-to-noise at higher frequencies. We also find variations in P/S ratios among the three main nuclear testing locations within the Semipalatinsk Test Site which, due to their nearly identical paths to BRVK, must be a function of differing geology and emplacement conditions.  相似文献   

8.
The global monitoring of earthquakes and explosions at decreasing magnitudes necessitates the fully automatic detection, location and classification of an ever increasing number of seismic events. Many seismic stations of the International Monitoring System are small-aperture arrays designed to optimize the detection and measurement of regional phases. Collaboration with operators of mines within regional distances of the ARCES array, together with waveform correlation techniques, has provided an unparalleled opportunity to assess the ability of a small-aperture array to provide robust and accurate direction and slowness estimates for phase arrivals resulting from well-constrained events at sites of repeating seismicity. A significant reason for the inaccuracy of current fully-automatic event location estimates is the use of f?k slowness estimates measured in variable frequency bands. The variability of slowness and azimuth measurements for a given phase from a given source region is reduced by the application of almost any constant frequency band. However, the frequency band resulting in the most stable estimates varies greatly from site to site. Situations are observed in which regional P- arrivals from two sites, far closer than the theoretical resolution of the array, result in highly distinct populations in slowness space. This means that the f?k estimates, even at relatively low frequencies, can be sensitive to source and path-specific characteristics of the wavefield and should be treated with caution when inferring a geographical backazimuth under the assumption of a planar wavefront arriving along the great-circle path. Moreover, different frequency bands are associated with different biases meaning that slowness and azimuth station corrections (commonly denoted SASCs) cannot be calibrated, and should not be used, without reference to the frequency band employed. We demonstrate an example where fully-automatic locations based on a source-region specific fixed-parameter template are more stable than the corresponding analyst reviewed estimates. The reason is that the analyst selects a frequency band and analysis window which appears optimal for each event. In this case, the frequency band which produces the most consistent direction estimates has neither the best SNR or the greatest beam-gain, and is therefore unlikely to be chosen by an analyst without calibration data.  相似文献   

9.
Development and Applications of Double-difference Seismic Tomography   总被引：7，自引：0，他引：7  
Double-difference (DD) tomography is a generalization of DD location; it simultaneously solves for the three-dimensional velocity structure and seismic event locations. DD tomography uses a combination of absolute and more accurate differential arrival times and hierarchically determines the velocity structure from larger scale to smaller scale. This method is able to produce more accurate event locations and velocity structure near the source region than standard tomography, which uses only absolute arrival times. We conduct a stability and uncertainty analysis of DD tomography based on a synthetic data set. Currently three versions of the DD tomography algorithms exist: tomoDD, tomoFDD and tomoADD. TomoDD assumes a flat earth model and uses a pseudo-bending ray-tracing algorithm to find rays between events and stations while tomoFDD uses a finite-difference travel-time algorithm and the curvature of the Earth is considered. Both codes are based on a regularly distributed inversion grid, with the former for a local scale and the latter for a regional scale. In contrast, tomoADD adapts the inversion mesh to match with the data distribution based on tetrahedral and Voronoi diagrams. We discuss examples of applying DD tomography to characterize fault zone structure, image high-resolution structure of subduction zones, and determine the velocity structure of volcanoes.  相似文献   

10.
—?In order to improve on the accuracy of event locations at teleseismic distances it is necessary to adequately correct for lateral variations in structure along the ray paths, either through deterministic model-based corrections, empirical path/station corrections, or a combination of both approaches. In this paper we investigate the ability of current three-dimensional models of mantle P-wave velocity to accurately locate teleseismic events. We test four recently published models; two are parameterized in terms of relatively long-wavelength spherical harmonic functions up to degree 12, and two are parameterized in terms of blocks of constant velocity which have a dimension of a few hundreds of km. These models, together with detailed crustal corrections, are used to locate a set of 112 global test events, consisting of both earthquakes and explosions with P-wave travel-time data compiled by the Internation al Seismological Centre (ISC). The results indicate that the supposedly higher resolution block models do not improve the accuracy of teleseismic event locations over the longer wavelength spherical harmonic models. For some source locations the block models do not predict the range of observed travel-time residuals as well as the longer wavelength models. The accuracy of the locations largely varies randomly with geographic position although events in central Asia are particularly well located. We also tested the effect of reduced data sets on the locations. Multiple location iterations using 30 P-wave travel times indicate that teleseismic events may be located within an area of 1000?km2 of the true location 66% of the time with only the model-based corrections, and increasing to 75% if calibration information is available. If as few as 8 phases are available then this is possible only 50% of the time. Further refinement in models and/or procedure, such as the addition of P n phases, azimuth data, and consideration of P-wave anisotropy may provide further improvement in the teleseismic location of small events.  相似文献   

11.
—?A set of procedures is described for estimating network-averaged teleseismic P-wave spectra for underground nuclear explosions and for analytically inverting these spectra to obtain estimates of m b /yield relations and individual yields for explosions at previously uncalibrated test sites. These procedures are then applied to the analyses of explosions at the former Soviet test sites at Shagan River, Degelen Mountain, Novaya Zemlya and Azgir, as well as at the French Sahara, U.S. Amchitka and Chinese Lop Nor test sites. It is demonstrated that the resulting seismic estimates of explosion yield and m b /yield relations are remarkably consistent with a variety of other available information for a number of these test sites. These results lead us to conclude that the network-averaged teleseismic P-wave spectra provide considerably more diagnostic information regarding the explosion seismic source than do the corresponding narrowband magnitude measures such as m b , M s and m b (L g ), and, therefore, that they are to be preferred for applications to seismic yield estimation for explosions at previously uncalibrated test sites.  相似文献   

12.
Nonlinear effects in seismic wave propagation are analyzed to determine the mechanical rigidity of different-order faults that thread the tectonic structures in the central part of the East European platform (Moscow syneclise and Voronezh Crystalline Massif) and the fault zones of the Balapan and Degelen mountain regions in Kazakhstan (the Degelen magmatic node in the Central Chingiz zone). The dependency of the rigidity of the fault zone on the fault’s length is obtained. The rigidity of the tectonic structures is found to experience well-expressed temporal variations with periods of 13–15 days, 27–32 days, and about one year. In the different-order fault zones, the amplitudes of both normal k n and the shear k s rigidity for semimonthly, monthly, and annual variations can span a factor of 1.3, 1.5, and 2.5, respectively.  相似文献   

13.
一种修定震源参数的方法   总被引：2，自引：1，他引：2       下载免费PDF全文
本文描述了空间域中的一种定位方法。此方法的主要特点是:1.震中位置与震源深度、发震时刻分离求解;2.震中位置的确定是采用Romney提出的曾融生改进的台偶到时差来建立最小平方条件方程,几乎不受结构的影响;3.震源深度和发震时刻的确定是采用慢度定深度、到时曲线时间截距定发震时刻的方法来实现的。本文用四川境内的5个工业爆破资料,作了方法试验并修定了近年发生的50个天然地震。修定后的震中位置更加靠近断裂带,走时残差减小了,震源深度呈现出沿龙门山断裂由北东向南西逐渐加深的规律性。  相似文献   

14.
利用广东地震台网的固定台和流动台记录的2次人工爆破事件,通过随机模拟台网几何形态,获得了该台网近震定位精度的经验性GT（Ground Truth）准则。结果表明：地震定位精度与台网几何形态密切相关;当台网满足以下条件时近震震中定位精度优于2km,震源深度精度优于3km,具有95%的置信度：（1）震中距小于150km的台站数≥7;（2）一级方位角空区<180°;（3）震中距小于10km的台站数≥1。在评估震源深度精度时,发现对于壳内地震,可靠的近台数据能够提高震源深度的精度,而定位时震中距较大的台站数量的增加对震源深度的精度影响很小。最后,应用该GT准则对广东地震台网产出的地震观测报告进行了评估,获得了1160个GT2参考事件。  相似文献   

15.
—?Improving the performance of short-period regional seismic discriminants by applying propagation corrections is explored using observations from two seismic monitoring stations in Asia. Frequency-dependent regional phase amplitude ratio measurements at stations NIL and ZAL for earthquakes and underground nuclear explosions were obtained from the prototype-International Data Center (pIDC) that has been established for developing monitoring capabilities of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The pIDC discriminant measurements have large scatter, much of which is attributed to wave propagation effects in the heterogeneous crustal waveguide. Linear regressions indicate that the phase ratios are correlated with topographic characteristics along the individual paths, providing an empirical means for correcting for path effects beyond conventional distance corrections. Kriging, a spatial multiple regression algorithm, also reveals coherent spatial patterns in the data indicative of regional path effects. Using available high-resolution topography data, correction of regional P/S ratios for the best models obtained from multivariate regressions systematically reduces the data variance relative to distance corrections alone, as has been observed for other data sets. The reduced scatter in the measurements increases the separation between earthquake and explosion populations in most cases, enhancing the regional discriminant performance. The path-corrected discriminants isolate explosions better for NIL than for ZAL, even though some of the explosion sources are located in a common source area. Kriging achieves comparable or superior variance reduction for the discriminant measures, without requiring knowledge of the path structure, although this may not result in improved discriminant performance. While always desirable, corrections for heterogeneous path effects may prove inadequate in some cases, notably when phase blockage occurs or when strong attenuation eliminates the diagnostic high-frequency energy.  相似文献   

16.
In the monitoring of earthquakes and nuclear explosions using a sparse worldwide network of seismic stations, it is frequently necessary to make reliable location estimates using a single seismic array. It is also desirable to screen out routine industrial explosions automatically in order that analyst resources are not wasted upon detections which can, with a high level of confidence, be associated with such a source. The Kovdor mine on the Kola Peninsula of NW Russia is the site of frequent industrial blasts which are well recorded by the ARCES regional seismic array at a distance of approximately 300 km. We describe here an automatic procedure for identifying signals which are likely to result from blasts at the Kovdor mine and, wherever possible, for obtaining single array locations for such events. Carefully calibrated processing parameters were chosen using measurements from confirmed events at the mine over a one-year period for which the operators supplied Ground Truth information. Phase arrival times are estimated using an autoregressive method and slowness and azimuth are estimated using broadband f{-}k analysis in fixed frequency bands and time-windows fixed relative to the initial P-onset time. We demonstrate the improvement to slowness estimates resulting from the use of fixed frequency bands. Events can be located using a single array if, in addition to the P-phase, at least one secondary phase is found with both an acceptable slowness estimate and valid onset-time estimate. We evaluate the on-line system over a twelve month period; every event known to have occured at the mine is detected by the process and 32 out of 53 confirmed events were located automatically. The remaining events were classified as “very likely” Kovdor events and were subsequently located by an analyst. The false alarm rate is low; only 84 very likely Kovdor events were identified during the whole of 2003 and none of these were subsequently located at a large distance from the mine. The location accuracy achieved automatically by the single-array process is remarkably good, and is comparable to that obtained interactively by an experienced analyst using two-array observations. The greatest problem encountered in the single array location procedure is the difficulty in determining arrival times for secondary phases, given the weak Sn phase and the complexity of the P-coda. The method described here could be applied to a wide range of locations and sources for which the monitoring of seismic activity is desirable. The effectiveness will depend upon the distance between source and receiver, the nature of the seismic sources and the level of regional seismicity.  相似文献   

17.
We have relocated seismic events registered within the Barents and Kara sea region from early twentieth century to 1989 with a view to creating a relocated catalog. For the relocation, we collected all available seismic bulletins from the global network using data from the ISC Bulletin (International Seismological Centre), ISC-GEM project (International Seismological Centre–Global Earthquake Model), EuroSeismos project, and by Soviet seismic stations from Geophysical Survey of the Russian Academy of Sciences. The location was performed by applying a modified method of generalized beamforming. We have considered several travel time models and selected one with the best location accuracy for ground truth events. Verification of the modified method and selection of the travel time model were performed using data on four nuclear explosions that occurred in the area of the Novaya Zemlya Archipelago and in the north of the European part of Russia. The modified method and the Barents travel time model provide sufficient accuracy for event location in the region. The relocation procedure was applied to 31 of 36 seismic events registered within the Barents and Kara sea region.  相似文献   

18.
通过人工爆破资料研究地球结构的独特优点是震源时间和位置精确知道.2010—2012年间福建省进行了一系列的爆破实验.本文利用手工拾取来自省地震台网记录的爆破地震初至Pg、Pn以及续至Pg波到时数据,采用联合反演方法构建了新的一维P波速度模型,即福建爆破模型(FJEM).与华南模型相比,FJEM模型对走时的拟合程度提高了45%,有明显改善.利用不同爆破地震数据组合得到稳定类似的福建地区一维速度模型,显示福建地区存在较简单的一维速度结构.对爆破地震的重定位显示传统使用的华南模型在福建地区具有较小的水平定位误差(平均0.52±0.45km),但存在较大深度误差(平均4.7±1.2km).FJEM模型表现出与华南模型相似的水平定位能力,但是震源深度误差更小(1.3±1.1km).对基于FJEM模型的合成天然地震目录的重定位,华南模型显示出相似的定位结果:(1)台站方位覆盖较好的福建中部地区的水平定位误差小;(2)台站方位覆盖差的福建海岸及海峡区域水平定位误差大;(3)震源深度误差则跟台站数目及方位分布没有明显的关系,而是与发震时间误差有互易关系.从中可以看出,地震水平定位误差基本上受台站方位覆盖影响,而受参考速度模型影响不大;而在深度方面,本文改进的FJEM模型不仅更加接近真实的速度结构(拟合走时更好)而且也减小了深度误差.因此建议在福建及其邻近区域的日常定位中用FJEM模型替代华南模型.  相似文献   

19.
—?A robust bearing estimation process for 3-component stations has been developed and explored. The method, called SEEC for Search, Estimate, Evaluate and Correct, intelligently exploits the inherent information in the arrival at every step of the process to achieve near-optimal results. In particular, the approach uses a consistent framework to define the optimal time-frequency windows on which to make estimates, to make the bearing estimates themselves, to construct metrics helpful in choosing the better estimates or admitting that the bearing is immeasurable, and finally to apply bias corrections when calibration information is available to yield a single final estimate. The algorithm was applied to a small but challenging set of events in a seismically active region. It demonstrated remarkable utility by providing better estimates and insights than previously available. Various monitoring implications are noted from these findings.  相似文献   

20.
Based on the first P wave arrival time data of local earthquakes recorded in the Kunming Telemetry Seismic Network in 1982–1989, the P travel time corrections of the stations in the network were obtained by use of the parameter separation method and the multiple event location method. This set of the corrections reflects the feature of lateral inhomogeneous structure of the upper crust beneath the network to certain degree. The geographic distribution of the sation corrections has obviously regional characteristics, by which the studied area is divided into three sub-areas. In the Western Yunnan area where the stations are the most dense, except the stations of Yunxian, Shidian and Wanding in south, the station corrections are not greater than 0.15 sec. In the eastern area (to the east of Chuxiong) where the network has slightly wider station interval, most of them show obviously positive delay. In southern area, including stations of Wenshan, Simao, Jinghong, Yunxian, Shidian and Wanding, all the stations have large negative delay. The results consist with the basic feature of geologic setting in Yunnan area. The accuracy of the relocated hypocentral parameters based on the corrected travel time data has fairly improved. Therefore the station corrections can be used to the routine processing of earthquake location in the Kunming Seismic Network. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 136–145, 1993.  相似文献   

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