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24 Οκτ 2013 (πριν από 3 χρόνια και 9 μήνες)

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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 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 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

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

Remote
Field
Station

Remote
Field
Station

Remote
Field
Station

Analog Signal
Reception

Analog/Digital
Converter

Time Sync

Digital Recording and
Data Processing System

Analog Data Transmission

MDN(BB)

DLVT

DBCT

DSHT

DVDT

DFBT

DMPT

DSTT

BBL

DWS(BB)

Dominica Sub
-
Nets

SVB (BB)

SVV

SSV

SLB

BHS


FCV

SFAN

St. Vincent Sub
-
Net

MCLT (BB)

SLDE

SLW

SLB

SLPA

SFAN

St Lucia Sub
-
Net

ALNG(BB)

SIP

BUAY

TRN(BB)

TBH

TPP

TPR

GRW

BOT

TCE

Trinidad Sub
-
Networks

GRHS(BB

GRW

GRIC

GRSS(2G)

GRCU

Grenada Sub
-
Net

BBSP(3DLPSP)

Barbados Station

BPA(BB))


MGH

MJBH

NEV

ANG

CPB

MRYT

Leeward Is Sub
-
Net

SKI(BB)

NVRH

NVBH

SKDB

BSK

SKTB

St. Kitts and

Nevis Sub
-
Net

STMA(BB)

STAT(3DSP)

SABT(3DSP)

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

~ 5 Minutes

Data Processing and Information Dissemination

End
-
to
-
End Time, ~ 25
-

30 Minutes


Digital Network

Digital
Field
Station

Digital
Field
Station

Digital
Field
Station

Digital
Field
Station

Time Sync

Digital Recording and
Data Processing System

Digital Data Transmission

Time Sync

Time Sync

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

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
-
Net

Proposed 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