Seismic Instrumentation Caribbean training course in Seismology and Tsunami Warnings 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:

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 X- axis 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.

Guralp CMG-3T Digital BB Seismometer Teledyne GS-13 SP Seismometer Streckeisen STS-2 Broadband Seismometer Contemporary Seismic Instruments Guralp CMG-T Accelerometer

Installation of a BB/SM Seismic Station in St. Vincent Location – Volcano ObservatoryClear 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

Spectrum of Seismic Instrumentation EQUIVALENT EARTH PEAK ACCELERATION ( 20 LOG M/SEC 2 ) 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 M6.5 Local events up to M5.3 Accelerometers are good for studying: Events of felt intensity including local events in excess of M8.0

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

Central Recording/Processing Site Hybrid Network Remote Field Station Analog Signal Reception Analog/Digital Converter Time Sync Digital Recording and Data Processing System Analog Data Transmission

Dominica Sub-Nets St. Vincent Sub-Net St Lucia Sub-Net Trinidad Sub-Networks Grenada Sub-Net Barbados Station Leeward Is Sub-NetSt. Kitts and Nevis Sub-Net N. A. Stations FTP SERVER Data Repository Seismic Research Unit: Network of Seismic Stations

Download Buffer Files Extract and Process Seismograms Disseminate Information to Disaster Preparedness Coordinators & Media Determine Preliminary Earthquake Parameters ~2-3 Monitors, ~ 10 Minutes ~ 10 Minutes ~ 5 Minutes Data Processing and Information Dissemination End-to-End Time, ~ Minutes

Digital Network Digital Field Station Time Sync Digital Recording and Data Processing System Digital Data Transmission Time Sync

Digital Station Clock to Timestamp Data On Sensor DAS to convert electric current to numbers for a computer to process Digital Comms Analysis and Storage PC to configure System Power Supply may be solar or Mains

Central American Broad Band Seismic Network, Mexico IMS Puerto Rico Galapagos/Ecuador Venezuela Colombia Cocos Isl. Not functioning IRIS Operating, on line Yucatan Under Construction

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

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 SurOccidente (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 - OVSICORI- UNA 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

Use of Digital BB Instrumentation in Sub-regional Seismic Networks Venezuelan Net SRU Net in the EC Nicaraguan Net

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 Global Networks

French GEOSCOPE Network

Dom. Rep Puerto Rico Haiti Jamaica Barbados Tobago Trinidad Grenada St. Vincent St. Lucia Aves Is. Dominica Turks and Caicos Is. Cocos Is Proposed GSN Stations Proposed USAID/GOTT/UWI Sub-Net Various Existing local BB Stations Proposed Cayman Sub-NetProposed Dutch Antillean Sub-Net Network Proposed at RSNO Workshop Guadeloupe Martinique Panama El Salvador Costa Rica Colombia Belize Nicaragua Mexico Honduras San Andres Is. Guatemala Cayman Is. Bahamas Existing GSN Stations Existing and Planned Real-Time Broadband Seismic Network

Key Closing Points 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 Modern Seismological Instrumentation