Seismic Instrumentation Caribbean training course in Seismology and
Seismic Instrumentation Caribbean training course in Seismology and Tsunami Warnings 25 -30 June, 2007 University of the west Indies St. Augustine Trinidad and Tobago
Seismic Monitoring • Seismology is a fundamental tool for investigating the kinematics and dynamics of geological processes at all scales • It involves the propagation of seismic waves through the Earth • Provides detail measurements made at the surface that suggest or imply what is happening at depth
Wave Propagation and Seismograms
Sources of Seismic Waves • • • earthquakes, volcanic eruptions, weather and ocean waves, meteorite impacts, cultural activities, underground nuclear explosions.
Instrumental Characteristics Different instruments can access different zones within the overall strain field of the plate boundary. Source: http: //www. earthscope. org
Simple Seismograph The seismometer together with the unit recording the signal is called a seismograph. The seismometer senses the ground vibration and converts this to a signal that can be recorded. Seismographs can detect, amplify, and record ground vibrations too small to be perceived by human beings. Modern seismographs can measure movements smaller than one nm.
Definitions Seismometer: • A seismometer is a sensor used to detect weak ground motion. The most common type of seismometer is made from a pendulum or a mass mounted on a spring. While seismometer is often used synonymously with "seismograph“, strictly speak, it is usually the component of a seismograph (definition follows) that senses the ground motion. Seismograph: • A sensitive instrument that can detect, amplify, and record ground vibrations too small to be perceived by human beings. Seismographs are primarily used to record the motion of the ground produced by earthquakes. Seismogram: • A graph showing ground motion versus time. On a seismogram, the Xaxis denotes time while the Y-axis denotes ground displacement. Accelerograph • A ground motion recorder whose output is proportional to ground acceleration • Typically used to record very strong ground motion useful in engineering design; seismographs commonly record off scale in these circumstances.
Contemporary Seismic Instruments Guralp CMG-T Accelerometer Guralp CMG-3 T Digital BB Seismometer Streckeisen STS-2 Broadband Seismometer Teledyne GS-13 SP Seismometer
Installation of a BB/SM Seismic Station in St. Vincent Location – Volcano Observatory Clear view for VSAT Excavate hole for power cable and sensor vault
Installation of a BB/SM Seismic Station in St. Vincent Vault Construction and Seismometer Installation
EQUIVALENT EARTH PEAK ACCELERATION ( 20 LOG M/SEC 2 ) Spectrum of Seismic Instrumentation PERIOD (SECONDS)
Bandwidth and Dynamic Range
Weighing In Earthquakes Broadband sensors are good for studying: Large – Great events at teleseismic distances Regional events up to M 6. 5 Local events up to M 5. 3 Accelerometers are good for studying: Events of felt intensity including local events in excess of M 8. 0
Applications for Seismic Instruments • As a tool to monitor and study volcanoes • Early warning systems – tsunami, volcanic eruptions • To investigate the dynamic response of structures • To study and monitor regional seismicity in an effort to access the earthquake hazard potential - provisions for building code design parameters for critical facilities to inform land use policies and mitigation plans to inform emergency preparedness plans
Evolution of Seismic networks • Autonomous Seismographic Stations – Poor timing – Data processing cumbersome • Analog Micro-earthquake Networks – Improved Timing – Limited Dynamic Range and Data Processing • Hybrid Micro-earthquake Networks – Limited dynamic range – Improved data processing • Digital Seismograph Networks – Vastly improved dynamic – Very good accuracy – Versatile processing but size usually limited • Virtual Seismograph Networks – Many of the good attributes listed above
Analog Seismic Stations Wilmore photographic seismograph
Components of a Micro-earthquake Network
Hybrid Network Remote Field Station Analog Signal Reception Time Sync Remote Field Station Analog Data Transmission Remote Field Station Analog/Digital Converter Digital Recording and Data Processing System Remote Field Station Central Recording/Processing Site
Seismic Research Unit: Network of Seismic Stations St. Kitts and Nevis Sub-Net STMA(BB) STAT(3 DSP) Leeward Is Sub. Net BPA(BB)) DWS(BB) SKI(BB) MGH NVRH SABT(3 DSP) MDN(BB) MJBH DLVT NVBH MRYT DBCT BSK NEV DSTT SKDB ANG DSHT SKTB N. A. Stations Dominica Sub. Nets DFBT CPB Data DVDT DMPT Repository BBL FTP TRN(BB) SERVER TBH BBSP(3 DLPSP) TPR Barbados Station GRW BOT TPP GRHS(BB SVB (BB) GRW SVV GRIC SSV TCE ALNG(BB) SIP BUAY Trinidad Sub. Networks MCLT (BB) GRSS(2 G) GRCU Grenada Sub. Net SLDE SLW SLB SFAN BHS FCV St. Vincent Sub-Net SFAN SLPA St Lucia Sub-Net
Data Processing and Information Dissemination Download Buffer Files ~2 -3 Monitors, ~ 10 Minutes Extract and Process Seismograms Determine Preliminary Earthquake Parameters Disseminate Information to Disaster Preparedness Coordinators & Media ~ 10 Minutes ~ 5 Minutes ~5 Minutes End-to-End Time, ~ 25 - 30 Minutes
Digital Network Digital Data Transmission Digital Field Station Time Sync Digital Recording and Data Processing System
Digital Station Clock to Timestamp Data Digital Comms On Sensor DAS to convert electric current to numbers for a computer to process Analysis and Storage PC to configure System Power Supply may be solar or Mains
Central American Broad Band Seismic Network, Yucatan Puerto Rico Mexico IMS Operating, on line Not functioning Venezuela IRIS Under Construction Colombia Cocos Isl. Galapagos/Ecuador
Caribbean Seismic Networks Many countries have realized the importance of seismic monitoring of their territories. There are over 30 seismological institutions and several hundred channels of data in the Caribbean
Seismic Networks Covering the Caribbean Region • • VENEZUELA Laboratorio de Geofísica, Universidad de los Andes (UAV) Fundación Venezolana de Investigaciones Sismológicas -FUNVISIS Centro de Sismología, Universidad de Oriente - (UDO) • • • EASTERN CARIBBEAN Seismic Research Unit (SRU), UWI IPG Observatoire Geophysique (IPG) Dominica Public Seismic Network – DPSN Montserrat Volcano Observatory (MVO) • • NORTHERN CARIBBEAN Red Sísmica de Puerto Rico (PRSN) Instituto Sismologico Universitario (ISU) Red Sísmica Dominicana Jamaica Seismograph Network, UWI, Mona Centro Nacional de Investigaciones Sismológicas-CENAIS Cayman Is. Network
Seismic Networks Covering the Caribbean Region COLUMBIA • CADAFE, Desarrollo Uribante Caparo-DESURCA (DESU) • Observatorio Sismológico del Sur. Occidente (OSSO) • Red Sísmica Nacional De Colombia - INGEOMINAS • Universidad del Valle (UVC) CENTRAL AMERICA • Instituto de Geociencias, Universidad de Panamá (UPA) • Observatori Vulcanológico y Sismológico de Costa Rica - OVSICORIUNA • Red Sismológica Nacional, Univ. de Costa Rica (UCR) • Unidad de Amenazas y Auscultación Sísmica y Volcánica Instituto Costarricense de Electricidad (ICE) • Sección de Sismología, Universida de Oriente (UCR) • Universidad Nacional, Campus Omar Dengo (HDC)
Seismic Networks Covering the Caribbean Region CENTRAL AMERICA (Cont’d) • Instituto Nacional de Sismología, Vulcanología, Meteorología e Hidrología - INSIVUMEH (GCG) • Instituto Nicaragüense de Estudios Territoriales – INETER • Universidad Nacional Autónoma de Honduras (UNAH) MEXICO • Red Sismológica Nacional de México - MNSN (MX) • Servicio Sismológico Nacional, Instituto de Geofísica, UNAM GLOBAL • Global Seismic Network, Albuquerque Seismological Laboratory, US • Comprehensive Test Ban Treaty IMS • French GEOSCOPE Network
Nicaraguan Net Use of Digital BB Instrumentation in Sub-regional Seismic Networks SRU Net in the EC Venezuelan Net
Global Networks IRIS/USGS GLOBAL NETWORK - USGS Albuquerque Seismological Laboratory - IRIS/IDA Group at IGPP, Scripps Institution of Oceanography University of California, San Diego - University Networks and Affiliates
French GEOSCOPE Network
Existing and Planned Real-Time Broadband Seismic Network Bahamas Mexico Turks and Caicos Is. Cayman Is. Jamaica Belize Guatemala El Salvador Puerto Rico Haiti Dom. Rep Honduras Aves Is. Nicaragua St. Lucia St. Vincent Grenada San Andres Is. Costa Rica Panama Colombia Proposed Dutch Antillean Sub-Net Barbados Tobago Trinidad Cocos Is Proposed GSN Stations Proposed USAID/GOTT/UWI Sub-Net Guadeloupe Dominica Martinique Various Existing local BB Stations Network Proposed at RSNO Workshop Proposed Cayman Sub-Net Existing GSN Stations
Key Closing Points Modern Seismological Instrumentation • Are very sensitive and can represent ground motion very accurately – More qualitative research • Remain on-scale for large events. Data can be processed rapidly – Applicable for Early Warning Systems • Instrument networks are more scalable and versatile – Can support the operation of multiple monitoring applications – Easy to extend coverage beyond national boundaries
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