Real time earthquake monitoring for early warning of tsunamis

Transcription

1 Real time earthquake monitoring for early warning of tsunamis 2 nd R.S.Dattatrayam India Meteorological Department Ministry of Earth Sciences New Delhi nd India Disaster Management Congress November, 2009, Vigyan Bhavan,, New Delhi RECENT EVENTS Pakistan (2005), 7.4, 1309 Sumatra (2004), 9.3, Bhuj (2001), 7.7, Chamoli (1999),6.8, 103 Jabalpur (1997), 6.0, 39 Latur (1993), 6.3, 7601 Uttarkashi (1991), 6.6, 769 (Casualties in India: 34, 375) Magnitude and more Seismicity of India and it s Neighborhood (1505- March 2005) SEISMOLOGY PHYSICS OF EARTH S INTERIOR HAZARD & RISK EVALUATION FOR EARTHQUAKE DISASTER MITIGATION PLANNING & PREPAREDNESS EARTHQUAKE DISASTER MITIGATION EARTHQUAKE MONITORING EARTHQUAKE PREDICTION (?) PHYSICS OF EARTHQUAKE PROCESSES SEISMOLOGICAL RESEARCH & DEVELOPMENT EARTHQUAKE PRECURSOR / PREDICTION RESEARCH Disaster Management (M>5.0) Hazard & Risk Assessment Research & Development (M>~1.5) Earthquake monitoring Users & Applications Public Information (M~3.0) Earthquake Monitoring Education & Awareness Early Warning of Tsunamis (M>6.5, under sea) Earthquake Engineering Earthquake Precursors / Prediction (M<1.5) IMD s s ROLE IN SEISMOLOGY As a nodal agency of GoI the primary role of IMD is to provide information on earthquake occurrences in and around India in least possible time for effective management of EARTHQUAKE & TSUNAMI DISASTERS National Seismological Network (55): (Including RTSMN) 30 Digital systems 25 Analog systems Present Operational Capability: M>3.5 - Peninsular Shield region. M>4.0 - Extra-Peninsular Shield region. M>5.0 - Border regions. M>2.0 - Delhi region, where a local network is in operation. M>6.5 - Capable of generating Tsunamis on Indian Coasts/ territories.

2 VSAT Based Seismic Telemetry Network around Delhi INAUGURATION OF TSUNAMI EARLY WARNING CENTRE ( ) Criteria used for estimation of Tsunamigenic potential Tsunamigenic earthquake sources Tsunamis are primarily caused due to large undersea Earthquakes. De pth of Location of M agnitude of Earthquake Earthquake Earthquake M>7.8 Potential for an ocean-wide destructive tsunami 7.8 M>7.5 Potential for a destructive regional tsunami 7.5 M>7.0 Potential for a destructive local tsunami 7.0 M 6.5 Very small potential for a destructive local tsunami Inland area M 6.5 No tsunami potential All locations M 6.5 No tsunami potential For a tsunami to hit Indian coast, it is necessary that a tsunamigenic earthquake occurs and its magnitude should be larger than M 7. Possible locations of such events are enclosed in ellipse Earthquakes with Slow Rupture Velocities are most efficient Tsunami Generators Makran (8.5) Nov. 27, 1945 Sea area <100km 75% of earthquake energy is released in the circum-pacific belt 900 Tsunamis in 20th Century Car Nicobar (7.9), Dec. 31, 1881 Sumatra (9.0) Dec. 26, 2004 > M7 20% in the Alpine-Himalayan belt 6 Tsunamis in 20th Century Java (7.8) July 17, 2006 Historical Tsunami in India 12 Apr, 1762 (BoB EQ) 1.8 M 31 Dec, 1881 (Car Nicobar EQ) 27 Aug, 1883 (Krakatoa) 2 M 26 Jun, 1941 (Andaman EQ) 27 Nov, 1945 (Makran EQ) 12 M 26 Dec, 2004 (Sumatra EQ) Landslides, Volcanoes & Meteor Impacts can also generate Tsunamis Tsunamigenic Pote ntial 100km 7.0 to Local 200 Km; 7.6 to Regional 1000 KM; > Ocean Wide >1000 KM Source parameters Origin time Propagation of Pwaves in Minutes Lat, Lon (Epicenter) Waveform data Depth, H (Hypocenter) Magnitudes (mb, Ml, Ms, MwP, Mm, Mw) Scalar moment Mo ->Mw Source time function (ζ) Slip distribution (source function, Mo) Moment tensor (φ, δ, λ, Mo, H) Tsunami simulations: pre-computed amplitudes Propagation of Tsunami waves in Hours

3 17 Broadband seismic stations with co-located accelerometers. 24-bit digital data acquisition systems. V-SAT communication to two CRSs at New Delhi and Hyderabad for realtime seismic waveform data transmission. Response-Hydra (V-1.47) Autolocation report generation & information dissemination through SMS, FAX, , IVRS & Website. Field Station Components Installations at field station (Port Blair) GPS Broadband Seismometer (Trillium-240) Symmetrical tri-axial 240 seconds(0.0042hz) to 35 Hz response Below NLNM from 100 seconds to 10 Hz Sensitivity of 1196v.s/m 40V P-P diff. Output 22 cm diameter, 16 cm high, 11 Kg weight 9 to 36v DC, power consumption 650mW Digital SOH Accelerometer (Make: Metrozet, Model No. TSA- SSA-01) Tri-axial Force-Balance Accelerometer Strong Motion Sensor: +/- 4 g Range Wide Bandwidth: DC to >225 Hz High Dynamic Range: 162 db at 1 Hz High Accuracy:0.0015% Total Non-Linearity Digitizer (Taurus with Trident) 6 channel 24 bit 40GB removable store Remote configuration Inbuilt GPS Receiver Windows WS for data analysis VSAT Communication (Make: Gilat) SkyEdge IP VSAT Ext. C band operation 32kbps bandwidth per field station 9-12V DC power operation, 25W 320W Solar Panel and Battery bank 17 field Stations 10 - Stations of WIHG, Dehradun (NAQS Server) & 80 - IRIS / GSN Network data (SEED link Server) System Overview Diagram- Central Receiving Station VSAT Internet Processing System NAQS Server-I SUN V490 Servers NAQS Server-II GLASS/ HYDRA (1) Windows XP Data Analysis GLASS/ HYDRA (2) SUN Storedge 3510FC Array 1 TB Ring Buffers -hard drives in RAID 5 configuration -0.5GB per ringbuffer(42 days of data) Event Publishing System (SUN Sparc45) Simultaneous Fax Waveform Display Event Display Website Updation Map showing the stations presently configured in RTSMN (including 10 WIHG stations and ~ 80 IRIS / GSN stations) SUN StorEdge C2 Autoloader -2TB (17stns + 10 stn WADIA data) Mobile IVRS SMS Dissemination System

4 Continuous Waveform Display Response Hydra Software - Features Developed by National Earthquake Information Center (NEIC), USGS. Generates immediate Alarm (sounding alert) based on first arrivals of phases from minimum 3 stations. Real-time picking of seismic phases; Near real time and post processing facilities. Provides fast, reliable and accurate locations and magnitudes for worldwide, regional and local earthquakes. Automatic and interactive modes of computation - Ml, MS, Mb, Mw, and Mwp magnitudes. Provides an easy method for interactive adjustment of automated P picks and magnitude determinations. Estimation of Centroid Moment Tensor (CMT) & Moment Tensor (MT) solutions. Velocity Model used for location - AK135 Global Velocity Model. Other Software modules can be added as required. Waveform and analyst displays for seismic processing. Event displays for operational monitoring. Redundancy and easy changeover between Primary & Secondary servers. VARIOUS TYPES OF MAGNITUDES ESTIMATED BY HYDRA SOFTWARE Many magnitude scales are now in use, each one being specific to type of seismic waves used for computation and / or size of event and hypocentral distance. Seven different types of magnitudes are computed by Hydra Software being used in RTSMN System: - ML, Mb, Md, MbLg, Ms, Mwp and Mw (CMT & MT). Tsunami Warning Systems employ techniques to compute the size of an event (Magnitude) in autolocation mode and in shortest possible time for early evaluation of tsunamigenic potential of large magnitude earthquakes. Response Hydra computes hypocentral parameters, only if, at least 5 quality P-phase picks are available from five stations. Type of magnitude Coda duration magnitude (Md) Richter (or) Local magnitude (ML) Body wave magnitude (mb) Surface wave magnitude (Ms) Body wave magnitude from Lg waves (MbLg) Moment magnitude (Mwp) Portion of the waveform used Complete duration of the waveform. Max. amplitude and corresponding period of S-wave. Max. amp. & corresponding period ( sec) within 15 cycles of P-wave. Surface waves in the period range of sec. Body waves in the period range of sec. 100 sec from P-wave onset. Epicentral distance No. of stations < 6º Not < 6º Not 15º - 100º Not 20º 160º Not 0.5º - 10º Not Focal depth Shallow focus Not <100º > 5 Not Mag. range General Remarks < 5.0 Good for small & local events. 6.0 Good for shallow focus earthquakes <800 km < 6.5 Good for deep focus earthquakes. <50 km Takes longer time ML and mb. <50 km < 6.5 Good for deep focus earthquakes Based on integrated P- wave & is the fastest estimate Contd.. from previous slide DISPLAY MAP OF EARTHQUAKE LOCATIONS Moment Tensor solutions Data used for calculation Wave frequency range Computation time Mw range Green s Functions Centroid Moment Tensor (CMT) Moment Tensor (MT) Body waves Surface waves secs secs. ~ minutes Computed during CMT calculations. No. of stations > 5. ~ 45 minutes Use pre-computed and stored values. No. of stations >5.

5 EARTHQUAKE INFORMATION DISSEMINATION (EID) FROM RTSMN SYSTEM Event parameters from Hydra RESPONSE HYDRA (v1.47) STATE PROCESSING UNIT OUTPUT (RAY PELLETS) Event Publisher (SUN Sparc 45 WS) Athena Event Publisher Event parameters and website content MySQL database Athena Event Win2003 Server Selection of Group of Addresses 1 st Level SMS Sends an on every Auto / Manual Location PULSE VOICE EID SYSTEM NANOMETRICS ATHENA PUBLISHER Auto- Located events AUTOMATIC ATHENA WEBSITE UPDATION (Access to limited internal users only) 1 st level SMS (Limited IMD Personnel Only) IMD Athena website Tomcat Web Server IMD website Published Event Verify params and Send MySQL database 2 nd Level SMS FAX IVRS IMD website update Few IMD personnel dealing with operations Manually Located events Scrutiny by Seismologist before Dissemination 2 ND level SMS PER BY FAX IVRS IMD WEBSITE UPDATATION Notification Dissemination of earthquake report through Mobile-SMS Level-1 Level-2 Interactive Voice Recording System (IVRS) (Tel. No )

6 English Press 1, for the latest Earthquake Information Press 2, for the previous Earthquake Press 3,for the largest Earthquake Press 4, for the Special bulletin 1 2 The latest event N Y 3 The previous event The largest event N N Y 4 Special bulletin Y Y There is no event Date of Earthquake Athena.jpg Time of Occurrence Magnitude on Richter scale Latitude.. Degree North/South Longitude.. Degree, East/ west Depth Kilometers Category.. Slight/Moderate/Great/Very Great Region Plays a special bulletin, if available N There is no special bulletin 3 For more information, please visit or Thank You End Call Athena Publishing Software RTSMN WEBSITE IMD WEBSITE FEW EXAMPLES OF AUTOLOCATED EVENTS (M:7.6)

7 Bhutan earthquake of 21st September, 2009 (Mw:6.1)

8 Comparative analysis of hypocentral parameters obtained in autolocation mode by RTSMN+IRIS & USGS Networks VARIOUS NETWORKS IN OPERATION FOR EARLY WARNING OF TSUNAMIS RTSMN DETECTION & LOCATION CAPABILITIES OF SEISMIC NETWORKS NETWORK DESIGN & OBJECTIVES. MAGNITUDE THRESHOLD - INTERINTER-STATION SPACING. SPACING. RTSMN+IRIS G E O F O N GLOBAL (GSN) AZIMUTHAL COVERAGE OF SEISMIC STATIONS WITH REFERENCE TO SEISMIC SOURCE BE UNIFORM IN SPACE. HYPOCENTRAL DISTANCE FROM THE NEAREST STATION, PARTICULARLY FOR ESTIMATION OF FOCUS. FOCUS. COMPUTATIONAL ACCURACIES & RMS ERRORS ARE DISTINCT FROM NETWORK CAPABILITIES AND RESULTS VARY FROM NETWORK TO NETWORK.

9 Comparison of Magnitude estimates by IMD (after scrutiny) and USGS Difference in epicentral locations of USGS and RTSMN+IRIS (Nov.,2008-Sept., 2009) Difference in focal depth between USGS and RTSMN+IRIS (Nov to Sept.-2009) difference in km Event ID Difference in focal depth (km) Event ID RMS error plot of locations by IMD COLLABORATIVE RESEARCH WITH MEXICO RMS error in seconds NEAR REAL-TIME ESTIMATION OF (a) LONG-PERIOD MAGNITUDE (b) MOMENT TENSOR AND (c) TSUNAMI POTENTIAL OF OFFSHORE EARTHQUAKES /09/2008;22:11 10/09/2008;13:08 08/09/2008;18:52 06/09/2008;05:47 04/09/2008;12:53 22/08/2008;07:21 19/08/2008;10:54 13/08/2008;14:49 10/08/2008;12:21 10/08/2008;08:20 5/8/2008;10:08 26/07/2008;16:50 20/07/2008;08:21 07/07/2008;09:58 29/06/2008;04:14 28/06/2008;15:29 27/06/2008;18:05 27/06/2008;11:40 15/06/2008;03:27 1/6/2008;07:39 Date and Time of the event (dd/mm/yyyy;hh:mm)

10 OBJECTIVE Develop and validate computer algorithms towards near real-time estimation of earthquake source parameters such as, long period magnitude & moment tensor and evaluation of tsunami potential of offshore earthquakes RATIONALE Large Magnitude, Shallow focal depth and Oceanic location Possible tsunami. Shallow depth + slow slip suggest that seismograms of tsunamigenic earthquakes may be, relatively, enriched at longer periods. In addition to long-period M and location of an event along the Sumatra-Andaman trench provided by RTSMN of IMD, what other parameter can be computed in <30 minute to better quantify tsunami potential of the earthquake? [Large M and oceanic location do not necessarily result in significant tsunami]. Can regional waveforms be used to discriminate between shallower and deeper events? Er Ratio of Broadband to high frequency energy, where, f 1 =0.01 Hz, f 2 =0.30 Hz, f 3 =2.00 Hz. DATA SET USED FOR PRELIMINARY ANALYSIS Preliminary Observations Solid circles:h>30km. Open cicles :H<30km. Er is a function of Mw. Larger Er Shallower depth. (M, Er) doublet is much more powerful discriminant than M alone. (M, Er) may provide better diagnostic than (M, Ms). If M 7 7 and Er 300 at VISK,, then high probability of tsunami genesis.. In fact, all such events in the dataset caused local tsunami 3m. If M 8.2,, then early tsunami warning, irrespective of Er value. Propose to implement the technique in real time mode.

11 CONCLUSIONS CONCLUSIONS Inclusion of IRIS stations in the RTSM Network has improved the locational capabilities in terms of better detection and relatively less error bars (with reference to USGS) both in location and magnitude for events outside the Indian network coverage. However, for earthquakes within and close to the mainland of India, the RTSMN system has proved to be very useful and effective. RTSMN+IRIS configuration could estimate the magnitudes for a relatively large number of events in comparison to RTSMN system alone. These estimates are broadly in good (+0.3 units of magnitude) agreement with those of USGS for majority of events. For majority of the events, the focal depths obtained from the RTSMN+IRIS network configuration compare well (within 25 kms.) with USGS as against RTSMN configuration alone. As regards response time, it is seen that the time taken for auto-location of events vary between 3 minutes for an event in Nepal to 13 minutes for an event in Java, Indonesia. The requirement of a scrutiny by a Seismologist, as recommended by ICG-IOTWS, is necessary and may add a few minutes for final dissemination. The overall time for dissemination with scrutiny may be ~ 20 minutes. As part of it s upgradation plans, IMD is in the process of extending the Real Time Seismic Monitoring capabilities for all earthquakes of M:3.0 and above in the mainland. UPGRADATION PLAN Proposed V-SAT based 20-station telemetry network for Northeast India OPTIMUM SEISMOLOGICAL NETWORK PROGRAM (177 stations) Thank you