Z ALISE - An Alert and nformationI System for Earthquakes ...
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GEOZENTRUM HANNOVER G Z H for arthquakes in Germany E ALISE - An ert and nformation ystem Al I S Impact Quantification Workflow Instrumental Intensity Vulnerability Consistency checks are used to assess the quality of the epicenter determination. The result of the spatial consistency is shown on the left. A numerical algorithm is used to calculate the consistency value Cp. This value quantifies the probability whether the epicenter location matches the distribution of stations contributing phases. Results of the automatic data processing with epicenter locations in the blue area are rejected. Event Grouping Consistency Checks and Quality Estimation Consistency Checks and Quality Estimation Hyposat Localization Impact Quantification Hyposat Localization Grid-Search Algorithm Initial Solution Near Real Time Waveform Data SSSSS- Signal-Definition - Dominant Frequency - Polarisation of Phases - f,k-Analysis for Array Data ... Waveform-Processing Information Handler Prepare Information for further Processing Bulletin Interactive Post- Processing and Quality Control Large Event ALERT STA/LTA Detector SSSSSPhase-Type Search Database Notify by Email / SMS - Source Parameter - Intensity Map - Vulnerability Map - Seismicity ... Create Webpage with Final Solution Database Geo- and Event Data Jackknife Phase Selection German Event Map Server ALISE is a newly developed earthquake alert and information system for Germany that consists of the following main components: A seismometer network of selected stations of the German Regional Seismic Network (GRSN) and two additional new stations. A communication system based on the CD1.0 protocol that enables near real-time transmission of waveform data from the seismometer stations to the central recording and processing system. Newly developed processing software for rapid and reliable event parameter determination. A tool for distributing alert messages via SMS and e-mail and to display the results automatically on the Web. An interface to a newly developed map server that provides detailed information on the epicenter region and the potential damage. Until today, two new seismic stations have been built northeast of Hannover and in central Germany close to Bad Hersfeld. The CD1.0 communication protocol ensures immediate access to the most recent data at any time, even after a acommunication link was disrupted. Data processing for the determination of seismic source parameters is the most important element of the alert system. The software makes use of improved procedures for seismic phase identification and phase association. Moreover, several consistency checks are included. The application of these automatic methods provides reliable estimate of the source parameters. A graphic user inter- face was developed for testing the algorithms of the automatic data processing. This tool is perfectly suited for processing both, near real time data and files with selected data sets of earthquakes with well known source parameters. The GUI acts as a front-end of the continuous detection process. Overview Graphic User Interface Initial Location Error Earthquake Test Data Signal Definition Multiphase Gridsearch Jackknife Analysis Consistency Checks Smoothed envelopes of seismograms are used to define the signal windows. These are needed by the waveform algorithms that compute varius signal parameters such as dominant frequency, polarization etc. A multiphase-gridsearch algorithm was developed to calculate a stable initial epicenter location which is required for subsequent signal analysis. The figure shows the computed fit between the phases an the corres- ponding grid points for an event in central Germany. The diagram below shows the fit as a function of distance from the epicenter. The magnitudes of selected events to test the performance of the alert system are ML>3.5 in Germany and ML> 4.0 outside. To quantify the impact of an earthquake in Germany the instrumental intensity (after MSK) is determined from the source parameters. Additionally, an estimate of the vulnerability is provided. This calculation takes the population density into account. The corresponding results for a fictitious magnitude 6.0 earthquake south west of Cologne are shown on the right.. After determination of the final epicenter location and estimation of the earthquake’s impact, the results are distributed via SMS and email and displayed on the Web together with additional statistical and geological information provided by the map server. Phases which bias the localization are determined and removed. This is done by a Jackknife method which performs localizations with a subset of all phases. From the change of the localization error the (good or bad) influence of the omitted phases is deduced. Finally, a set of good hypocenter solutions remain, shown in the figure by black rings whose diameters resemble the spatial error of the solution. Polarization Analysis Three component polarization analysis is applied to the seismic signals to determine the back azimuth. The quality of the results depends on the signal to noise ratio and on the geological conditions below the seismometer site. Results of polarization analysis are shown in the two figures above with a P-phase on the left and S-phase on the right side, respectively. Error of initial localization obtained for the test data set as a function of the gap. For events covered by the network with a gap < 180 deg the location difference is less than 30 km.
Transcript of Z ALISE - An Alert and nformationI System for Earthquakes ...
G E O Z E N T R U M H A N N O V E RG Z H
for arthquakes in GermanyE
ALISE - An ert and nformation ystemAl I S
Impact Quantification
Workflow
Instrumental Intensity Vulnerability
Consistency checks areused to assess the qualityof the epicenterdetermination. The resultof the spatial consistencyis shown on the left. Anumerical algorithm isused to calculate theconsistency value Cp.This value quantifies theprobability whether theepicenter locationmatches the distributionof stations contributingphases. Results of theautomatic dataprocessing with epicenterlocations in the blue areaare rejected.
EventGrouping
ConsistencyChecks and
QualityEstimation
ConsistencyChecks and
QualityEstimation
HyposatLocalization
ImpactQuantification
HyposatLocalization
Grid-SearchAlgorithm
Initial Solution
Near Real TimeWaveform Data
S1
S2
S3
S4
S5
- Signal-Definition- Dominant Frequency- Polarisation of Phases- f,k-Analysis for Array Data
...
Waveform-Processing
Information Handler
Prepare Information for furtherProcessing
Bulletin
Interactive Post-Processing andQuality Control
Large EventALERT
STA/LTADetector
S1
S2
S3
S4
S5
Phase-TypeSearch
Database
Notify byEmail / SMS
- Source Parameter- Intensity Map- Vulnerability Map- Seismicity
...
Create Webpage with
Final SolutionDatabase
Geo- andEvent Data
Jackknife PhaseSelection
German EventMap Server
ALISE is a newly developed earthquake alert and information system for Germany that consists ofthe following main components:
A seismometer network of selected stations of the German Regional Seismic Network (GRSN)and two additional new stations.
A communication system based on the CD1.0 protocol that enables near real-timetransmission of waveform data from the seismometer stations to the central recording andprocessing system.
Newly developed processing software for rapid and reliable event parameter determination.
A tool for distributing alert messages via SMS and e-mail and to display the resultsautomatically on the Web.
An interface to a newly developed map server that provides detailed information on theepicenter region and the potential damage.
Until today, two new seismic stations have been built northeast of Hannover and in centralGermany close to Bad Hersfeld. The CD1.0 communication protocol ensures immediate access tothe most recent data at any time, even after a acommunication link was disrupted.
Data processing for the determination of seismic source parameters is the most important elementof the alert system. The software makes use of improved procedures for seismic phaseidentification and phase association. Moreover, several consistency checks are included. Theapplication of these automatic methods provides reliable estimate of the source parameters.
A graphic user inter-face was developed fortesting the algorithmsof the automatic dataprocessing. This toolis perfectly suited forprocessing both, nearreal time data and fileswith selected data setsof earthquakes withwell known sourceparameters.The GUI acts as afront-end of thecontinuous detectionprocess.
Overview
Graphic User Interface
Initial Location ErrorEarthquake Test Data
Signal Definition
Multiphase GridsearchJackknife Analysis Consistency Checks
Smoothed envelopes of seismograms are used to define the signalwindows. These are needed by the waveform algorithms thatcompute varius signal parameters such as dominant frequency,polarization etc.
A multiphase-gridsearch algorithm was developed to calculate a stableinitial epicenter location which is required for subsequent signal analysis.The figure shows the computed fit between the phases an the corres-ponding grid points for an event in central Germany. The diagram belowshows the fit as a function of distance from the epicenter.
The magnitudes of selected events to testthe performance of the alert system areML>3.5 in Germany and ML> 4.0 outside.
To quantify the impact of anearthquake in Germany theinstrumental intensity (afterMSK) is determined from thesource parameters.Additionally, an estimate ofthe vulnerability is provided.This calculation takes thepopulation density intoaccount. The correspondingresults for a fictitiousmagnitude 6.0 earthquakesouth west of Cologne areshown on the right..
After determination of the final epicenter location and estimation of the earthquake’s impact, theresults are distributed via SMS and email and displayed on the Web together with additionalstatistical and geological information provided by the map server.
Phases which bias thelocalization are determinedand removed. This is doneby a Jackknife method whichperforms localizations with asubset of all phases. Fromthe change of the localizationerror the (good or bad)influence of the omittedphases is deduced. Finally, aset of good hypocentersolutions remain, shown inthe figure by black ringswhose diameters resemblethe spatial error of thesolution.
Polarization Analysis
Three component polarization analysis is applied to theseismic signals to determine the back azimuth. The quality ofthe results depends on the signal to noise ratio and on thegeological conditions below the seismometer site. Results ofpolarization analysis are shown in the two figures above with aP-phase on the left and S-phase on the right side,respectively.
Error of initial localization obtained for the test data set asa function of the gap. For events covered by the networkwith a gap < 180 deg the location difference is less than30 km.
