排序方式: 共有8条查询结果,搜索用时 0 毫秒
1
1.
The purpose of this study is to develop a technique to discriminate artificial explosions from local small earthquakes ( M ≤ 4.0) in the time–frequency domain. In order to obtain spectral features of artificial explosions and earthquakes, 3-D spectrograms (frequency, time and amplitude) have been used. They represent a useful tool for studying the frequency content of entire seismic waveforms observed at local and regional distances (Kim, Simpson & Richards 1994). P and S(L g ) waves from quarry blasts show that the frequency content associated with the dominant amplitude appears above 10 Hz and Rg phases are observed at close distances. P and S(L g ) waves from the Tongosan earthquake have strong amplitudes below 10 Hz. For the Munkyong earthquake, however, a broader frequency content up to 20 Hz is found.
For discrimination between small earthquakes and explosions, Pg/L g spectral ratios are used below 10 Hz, and through spectrogram analysis we can see different frequency contents of explosions and earthquakes. Unfortunately, because explosion data recorded at KSRS array are digitized at 20 sps, we cannot avoid analysing below 10 Hz because of the Nyquist frequency. In order to select time windows, the group velocity was computed using multiple-filter analysis (MFA), and free-surface effects have been removed from all three-component data in order to improve data quality. Using FFT, a log-average spectral amplitude is calculated over seven frequency bands: 0.5 to 3, 2 to 4, 3 to 5, 4 to 6, 5 to 7, 6 to 8 and 8 to 10 Hz. The best separation between explosions and earthquakes is observed from 6 to 8 Hz. In this frequency band we can separate explosions with log ( Pg/L g ) above −0.5, except EXP1 recorded at SIHY1-1, and earthquakes below −0.5, except the Munkyong earthquake record at station KMH. 相似文献
For discrimination between small earthquakes and explosions, Pg/L g spectral ratios are used below 10 Hz, and through spectrogram analysis we can see different frequency contents of explosions and earthquakes. Unfortunately, because explosion data recorded at KSRS array are digitized at 20 sps, we cannot avoid analysing below 10 Hz because of the Nyquist frequency. In order to select time windows, the group velocity was computed using multiple-filter analysis (MFA), and free-surface effects have been removed from all three-component data in order to improve data quality. Using FFT, a log-average spectral amplitude is calculated over seven frequency bands: 0.5 to 3, 2 to 4, 3 to 5, 4 to 6, 5 to 7, 6 to 8 and 8 to 10 Hz. The best separation between explosions and earthquakes is observed from 6 to 8 Hz. In this frequency band we can separate explosions with log ( Pg/L g ) above −0.5, except EXP1 recorded at SIHY1-1, and earthquakes below −0.5, except the Munkyong earthquake record at station KMH. 相似文献
2.
Introduction Seismic monitoring is one of the most important approaches for ground-based nuclear explo-sion monitoring (CTBTO, 1998). The trend in this research field is to improve the monitoring ca-pability for low magnitude seismic events in regional scales. Seismic monitoring mainly includes detection, location, identification and characterization of seismic events. The correctness and accuracy of all of them depend on the quality of seismic re-cords and the degrees of uncertainties of ge… 相似文献
3.
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
4.
5.
6.
7.
地震核查技术是《全面禁止核试验条约》规定的主要针对地下核爆炸监测的国际监测技术手段. 为了提高对低震级事件的检测、定位与识别能力,开发了禁核试核查地震信息系统. 该系统以ArcGIS为基础,充分发挥GIS的强大的空间数据分析、拓扑分析和数据可视化处理能力,为地震数据的分析处理建立灵活方便的图形化研究环境. 利用ArcSDE Geodatabase数据模型与大型关系数据库管理系统ORACLE相结合,并通过基于COM的ArcObjects组件开发技术扩展ORACLE的管理功能,真正实现了空间、非空间等多源数据的一体化无缝集成,并保留了ORACLE的海量数据管理、事务处理、记录锁定、并发控制、 数据仓库等功能. 本文主要论述禁核试核查地震信息系统的总体设计与相关技术. 相似文献
8.
1