IGUT Seismic Network Institute of Geophysics University of Tehran (IGUT) Mehdi Rezapour
History of seismic monitoring in Iran The IGUT starts to record & Locate seismic events in the 1960 s using 5 WWSSN type stations. Short-period, Hugo-Benioff-Modl-1051 Long-period, Spreng Nether Recording system: on microfilm & paper Teledyne Geotech
Iranian Long Period Array (ILPA) In 1975 a 7 station bore hole array with aperture of ~60 km installed in southwestern of Tehran. Each station equipped with three component BB seismometer (M38600) located in bore-hole with 100 m depth. Digital Data transmits to Tehran Recording system: magnetic tape, microfilm, paper Teledyne Geotech
Recording drums & M38600 seismometer
In the 1980 s, 6 other SP stations established Seismometer S-13
After the destructive Roudbar earthquake in 1990 (Ms=7.7), the IGUT was funded to establish seismic networks allover the country. 1- The first digital telemetric network consists of 12 three component stations operated in 1996 in the Tehran region. 2- The next local network established in late 1996 in Tabriz region with 8 stations. 3-..
Now the Iranian Seismological Center (IRSC) is running 4 SP3 Analogue stations S-13 3 BH Bore-hole M38600 6 BB Broad-band CMG-3T + ESP 60 SP3 (12 sub-networks) SS-1 in which two of them in addition to SS-1 equipped with BB CMG-3T 50Hz-300s seismometer
Data acquisition system Data are digitized by 24 bit, with 50 sam./s, Data transferred using 230-242 MHz radio The system alarms based on STA/LTA NAQS. Data processed using DAN software.
Location of the IRSC stations
Inside of a seismic station, SS-1 seismometers
Inside of a seismic station, SS-1 seismometers
RD3-16 HRD-24
A seismic station also, as a repeater station
Connecting IRSC with sub-networks via VPN & Satellite
Data processing Using DAN software in which for locating we can use Hypo71 or LOC programs Magnitude are determined using modified Nuttli formulae as: Where v is ground velocity in micron per seconds, and Δ is epicentral distance in Km. Km106ΔKm600For1.8)Δ2.5Log()4πvLog(Km50ΔKm106For0.1)Δ1.66Log()4πvLog(MN
Mn magnitude calibrated with mb of ISC (a) mb versus Mn. (b) Averaged mb-log(v/4π) values over 0.05 interval of log(δ).
Epicenters of occurred events with Mn>=1.0 in 2008
Future plan for expanding seismic stations
Main missions of the IRSC of the IGUT Record and monitor seismic events, then report occurred events to different organizations via TEL, FAX, SMS, Email, & etc. Create an easily accessible data base of earthquake information (catalog and waveform data, etc), for research in seismology and earth sciences, http://irsc.ut.ac.ir Run research projects in earthquake seismology and expand seismic networks in allover the country Cooperate with other organizations to mitigate the earthquake hazard through the recording, analysis, researches, exchanging data with other national and international agencies, and distribution of information
Access to IRSC data Everyone can download wave forms for events with magnitude Mn=>4.0. Access catalogue data such as arrival times (phase readings), amplitude, It is possible to download wave forms for some teleseismic events. We email catalogue data for many persons, national and International agenesis. http://irsc.ut.ac.ir
Conclusions Detection threshold inside each subnetwork is about Mn=1.0, but in allover country the detection threshold is about Mn=2.0. Investigation shows that each year more than 12 earthquakes with Mn>=5.0, and one earthquake with Mn>=6.0 occurred. The network need to expands (subnetwork or individual stations) to achieve a dense network and develop the acquisition system and software's.
It is necessary to exchange data with other national and regional networks to improve locating of occurred events in the border region of country.
Other network International Institute of Earthquake Engineering and Seismology (IIEES) have a network with 14 stations in allover the country.