The Strong Motion Network: Synergy with the broadband seismic network

Ioannis Kalogeras, Nikolaos Melis and Christos Evangelidis

NATIONAL OBSERVATORY OF ATHENSINSTITUTE OF GEODYNAMICSP.O.BOX 20048, 11810 ATHENS

The geodynamic model in the broader area

NOAIG strong motion network till 2009

From 70s to 2009

Installations mainly in urban areas,

11-12bits instruments

NOAIG strong motion database updated till today for the stations and for records from the triggering mode instruments

Data availableupon request

• Local arrays have been implemented with the support of other organizations (municipalities, public organizations etc).• Development of strong motion databases and dissemination of data.• Establishment of a system for the telemetric maintenance of the network via the network of Hellenic State, aiming to enhance “traditional” accelerographic instruments equipped with serial interfaces.

The NOAIG strong motion network till 2009

LAN2Mbps

NATIONAL OBSERVATORY OF ATHENS

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2 – 34 Mbps

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BUILDING WITH SYZEFXIS CONNECTION

VPN1, VPN2, ….

RouterΣΥΖΕΥΞΙΣ SYZEFXIS NET

REMOTE ADSL

2Mbps

TOWN HALL KASTELLORIZO

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2 Mbps/ 512kbbs

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Institute of Geodynamics & Syzefxis

New Hellenic Accelerographic Network

Since 2009, NOAIG and ITSAK were financially supported by EPPO (i.e. national funds) in order to purchase modern accelerographs and to install them in the Hellenic territory aiming among others to:

• densify the national network

• homogenize the processing procedure

• disseminate the data as soon as possible after the occurrence of a strong earthquake

Within this project, the 2 Institutions almost doubled the number of installed instruments reaching a total number of about 350 by 2012.

New Hellenic Accelerographic Network (II)

The criteria of new installations are:

• Communication between the 2 Institution in order to avoid overlapping (establishment of a Committee for the development and operation of the National Accelerographic Network)

• Coverage of main cities (population > 5000) – larger cities with more than one instruments at different geological conditions – urban development

• Coverage of areas of high seismicity

• Coverage of large seismotectonic lines

• Coverage of areas according to hazard studies (ex. long term prediction)

• Coverage of sites of specific interest (large constructions, archaeological sites)

Example of a free-field installations

Example of in-building installations

Strong motion data archival, dissemination and storage

The instruments in triggering mode produce data which are easily stored and disseminated, since they are small files.

Our philosophy for strong motion records should be changed with the new-generation-instruments since they show the following:

• real-time transmission and in continuous mode

• they should processed not only as strong motion records but also as weak motion signals like the one from seismographs (miniseed format)

• 24bits 200-250s/s means about 100Mb per instrument per day or more than 10Tb per year for 300 instruments of that type at a national scale.

The new generation strong motion instruments should be integrated into the seismic network

Development of a new web page for monitoring the accelerographic network

A record example of the new strong motion network:A SE Aegean Sea intermediate depth earthquake,

April 1st, 2011, 13:29, M6.0, h=69km

Strong motion records from distances between 40 and 750km and pga between 130 and 0.1mg (no missing triggers)

The Japan earthquake, March 11 2011, M9.0, R=9500km

as recorded by an STS2 seismometer at NOAIG (ATH HHZ), and as calculated by de-convolution of the strong motion record from a CMG-5TD accelerograph at the same site (NOAC HNZ)

Health monitoring of the continuous recording strong motion stations via the PQLX software

The grey lines are the high and low noise level of Peterson’s model (1993). At high frequencies (<0.1s) the site noise is measured (artificial noise). Between 1 and 5s is the instrument noise and between 5 and 10s is the microseismic noise.

The red line represents the Low Noise Model and the grey area the 80% confidence intervals. The red line is the criterion for a station to be characterized as a good station for phase picking within the automatic location system.

For method see Evangelidis & Melis (2012)

Calculated noise model for Greece, based on the statistical mode of the PDF noise levels of all the 75 strong motion stations.

An example of a “quiet” and a “noisy” station

Strong Motion Stations that complements the BB HUSN network and used in the 24/7 analysis at NOAIG for hypocenter and magnitude determination.

These strong motion stations are not only “quiet” ones, but they cover “holes” of the seismic network as well.

Automatic NOAIG Mw and Focal Mechanism determination using Strong Motion stations within MWNEAR and FMNEAR method

(Delouis et. al. 2009, BSSA)Spectral estimation Grid search Waveform inversion

NOAIG Moment Tensor determination using Strong Motion stations:Routine analysis using ISOLA (Sokos and Zahradnik, 2007)

Local seismic networks (like the portable seismic networks) or strong motion arrays can be accommodated on the central system in real-time

operational mode helping the operational role of NOAIG.

Seismic Network

Sea-level Network

Acquisition, Automatic Processing, Auto Reporting,

Manual Verification, Publication

SeisComP3

Sea – Level Soft

TAT

General Secretariat for Civil ProtectionEarthquake Planning and Protection Organization

24/7 Operational System at NOA - HLNTWC

Tsunami Model Database

GIS PlatformQuake Alerting

Alerting

GTSvia HNMO

real time seismic dataGFZ, INGV, ORFEUS, IRIS

Earthquake and Tsunami Database

UNESCO/IOC/ICG/NEAMTWS: CTWP, TNC, TWFP, EMO

Other Publishing Tools

Com Test Tools

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Near future steps

•Continuous improvement of data storage and processing, towards a semi-automatic procedure,

•Determination of data dissemination policies (ex. web hosted database for registered access),

•Improvements on the use of the strong ground motion records in conjunction with the information from seismological and macroseismic networks.

• Reliable ground motion prediction equations and site effects

• Shake maps

Thank you for your attention