Tsunami Detection System Nick Street, Project Engineer David Mould, Presenter.

Tsunami Detection System Nick Street, Project Engineer David Mould, Presenter

Agenda 1. Need for Tsunami Detection System 2. System Overview 3. Tsunami Detection System requirements 4. Seabed Unit - Tsunameter 5. Surface Unit - Transceiver 6. Satellite Modem Link 7. Data Examples 8. Acoustic telemetry overview 9. Q&A

Need for Tsunami Detection System As a result of the Boxing Day 2004 Tsunami the owner of Sonardyne, John Partridge, decided that Sonardyne should look to producing a Tsunami Detection System to help give early warning of a potential life and property damaging event.

System Overview The system consists of a seabed pressure monitoring transponder, a surface buoy with a data collection unit that passes the acoustic message to a satellite telephone system and then onwards to the shore base.

What Do We Need To Detect? At the Beach easy to detect but to late Nearing the coast, easy to detect but still to late In deep water very hard to detect against the natural sea surface movement, but this is the only option that gives enough early warning time

Tsunami Detection System Requirements Pressure sensor Detection Algorithm Acoustic Link Long battery life Release mechanism Floatation Satellite modem

Tsunami Detection Algorithm Based on NOAA algorithm Predicted pressure calculated from previous 3 hour history, using 10 minutes from each hour (adapted for slow wave) Detection criteria: C-O > threshold for 2 consecutive samples. - 3cm used for threshold. Spike filter single reading > 10cm ignored Detection threshold can be changed by acoustic command An Event can be forced or cancelled by acoustic command.

Tsunami Detection System 1. Need for Tsunami Detection System 2. System Overview 3. Tsunami Detection System requirements 4. Seabed Unit - Tsunameter 5. Surface Unit - Transceiver 6. Satellite Modem Link 7. Data Examples 8. Acoustic Telemetry Overview 9. Q&A

Subsea Unit Tsunameter Based on instrumented survey transponder Compatt 5 Paroscientific Digiquartz pressure sensor Acoustic data link - High speed 1kb/s - Forward Error Correction (FEC) - Wideband technology Lithium battery pack 2 year operation Integral acoustic release Floatation collar Thousands of operational deployments Single pressure housing

Advantages of a Single Subsea Unit No requirement for level seabed No subsea cables and connectors Lighter easier deck handling In-house control over entire system Rapid modifications Simplified testing Re-use of existing parts Track record 1000 s deployments Proven battery life Engineering support

Tsunameter - Sensor Electronics Paroscientific Digiquartz sensor - 10 000psi (6800m) range - Or 6000psi (4000m) range - Temperature compensated - Extremely high repeatability under stable thermal conditions Platinum Resistance Thermometer for sea water temperature Release motor Memory card

Tsunameter Deployment in the Bay of Bengal

Surface Unit - Transceiver Lightweight - 9kg in water Low power - 1W at 24V Wideband signal technology Integral Li+ battery Armoured cable to buoy Optional acoustic baffle 5km+ acoustic range > Buoy mounted transceiver with side noise shield that connects to satellite telephone system

Satellite Modem Link 2-way communication link Allows direct control of transceiver Allows acoustic commands to be sent to subsea unit - to alter set-up parameters - diagnostics - to Force or Cancel Events Not included in Sonardyne scope of supply

Tsunami Detection System 1. Need for Tsunami Detection System 2. System Overview 3. Tsunami Detection System requirements 4. Seabed Unit - Tsunameter 5. Surface Unit - Transceiver 6. Satellite Modem 7. Data Examples 8. Acoustic Telemetry Overview 9. Q&A

Data Example - Acoustic SMS Messages Hourly pressure data 4 readings averaged over 15 minutes Hourly status data battery, sea water temp. SMS format (Sonardyne Messaging Service) for short text messages: Identifies data source address ASCII message delivered securely Pressure Log Status YMDHMS Type 1 (Hourly) P1 P2 P3 P4 SMS:0102,0 061021170000;1,39866;1,40022;1,40157;1,40288 SMS:0102,0 V142,U019,B0,O0,T0,S+1550, SMS:0102,0 061021180000;1,40394;1,40492;1,40569;1,40635 SMS:0102,0 V142,U019,B0,O0,T0,S+1550, Tpdr ID F/W Version % Used Battery Alarm Battery On Tilt Temperature Up to 128 ASCII characters for customer defined message

Data Example - Hourly Pressure Messages Acoustic data hourly message, data points every 15 minutes 42000 41000 Raw abs. pressure (10Pa) 40000 39000 38000 37000 36000 35000 34000 18:00 00:00 06:00 12:00 18:00 00:00 Date Time

Logged Data Analysis Raw abs pressure (Pa) 144000 143900 143800 143700 143600 143500 143400 143300 143200 143100 143000 142900 142800 142700 142600 142500 142400 142300 142200 142100 142000 Vertical scale: 1 div ~ 1cm Measured Predicted Diff (C-O) Simulated Event: measured vs predicted, data from memory card (Difference rebased to 142600) detection point detection threshold 09:20 09:30 09:40 09:50 10:00 3 cm

Data Recovery Tsunameter: Full Event Cycle Standard mode: Type 1 message containing 4 readings averaged over 15 minutes sent every hour Event mode: 1x Type 2 message containing 4 x 15s consecutive readings 2 before & 2 during Event) Extended reporting mode: 36x Type 3 messages containing10 readings, 30s apart (sent every 5 minutes) t- 60 t 0 t 60 t 120 t 180 t 240 Time (minutes)

Event - Data Recovery Tsunameter: records telemetered during Event Extended reporting mode: 36 x 10 x alternate 15s readings Event mode: 4 x 15s readings Key: t -2 t -1 t 0 t 2 t 3 Time (minutes) t 1 t 4 t 5 t 6 t 7 t 8 t 9 t 10 t 11 t 12 One acoustic message A single raw pressure value One reading made every 15 seconds

Acoustic Data from Plymouth Trial 30 Metres 42000 Tsunami C5 acoustic data: Plymouth 18-21 Sept sent via SMS (vertical scale 1m/div) 41000 Another detection at 07:07 40000 Unit recovered to surface Raw abs pressure (10Pa) 39000 38000 37000 Event detection at 01:08 starts rapid data telemetry for 180 minutes 36000 35000 34000 18/09/2006 19/09/2006 20/09/2006 21/09/2006 22/09/2006 23/09/2006

Sea Trial Data 600 Metres Sonardyne sea trial - 600m 610200 610100 610000 609900 609800 Absolute pressure (10Pa ~mm) 609700 609600 609500 609400 609300 609200 609100 609000 608900 608800 608700 608600 16/02/2007 17/02/2007 18/02/2007 19/02/2007 20/02/2007 21/02/2007

NIOT Tsunami Buoy Locations Buoy TB10 which sent the following data

NIOT Battery Life Test 3852000 Sonardyne data: Nicobar earthquake 25/07/07 Station: TB10-7 deg 1'N 87 deg 4'E Source: 7.08N 92.59E Magnitude 6.2 3851900 3851800 Abs pressure (1mm ~ 10 Pa) 3851700 3851600 3851500 3851400 3851300 3851200 3851100 Vertical scale ~10cm/div 3851000 15/07/2007 17/07/2007 19/07/2007 21/07/2007 23/07/2007 25/07/2007 27/07/2007 Real event caused NIOT to be concerned about battery life

The Event Two Hours Before Sonardyne data: Nicobar earthquake 25/07/07 Station: TB10-7 deg 1'N 87 deg 4'E Source: 7.08N 92.59E Magnitude 6.2 3851690 3851680 3851670 3851660 Abs pressure (1mm ~ 10 Pa) 3851650 3851640 3851630 3851620 3851610 3851600 3851590 3851580 Vertical scale ~1cm/div 3851570 3851560 21:30:00 21:45:00 22:00:00 22:15:00 22:30:00 22:45:00 23:00:00 23:15:00 23:30:00 23:45:00 00:00:00 00:15:00 00:30:00 The regular 15 minute interval logs that are sent once per hour Event data takes priority over 15 minute interval logs from the hour in which the event occurs, hence with event just before the hour the ¼, ½ and ¾ hour records are not sent

The Event - Post Event Data 3851700 Sonardyne data: Nicobar earthquake 25/07/07 Station: TB10-7 deg 1'N 87 deg 4'E Source: 7.08N 92.59E Magnitude 6.2 3851690 3851680 3851670 3851660 Abs pressure (1mm ~ 10 Pa) 3851650 3851640 3851630 3851620 3851610 3851600 3851590 3851580 3851570 3851560 Vert. scale: ~1cm/div 3851550 23:00:00 23:10:00 23:20:00 23:30:00 23:40:00 23:50:00 00:00:00 00:10:00 00:20:00 00:30:00 00:40:00 00:50:00 01:00:00 Data points passed on by NIOT satellite phone system

The Event National Media Coverage

Tsunami Detection System - Requirements 1. Need for Tsunami Detection System 2. System Overview 3. Tsunami Detection System requirements 4. Seabed Unit - Tsunameter 5. Surface unit - Transceiver 6. Satellite Modem Link 7. Data Examples 8. Acoustic Telemetry Overview 9. Q&A

A Tone signal Single Frequency No modulation Defined duration

A Wideband Signal Single carrier Frequency Phase modulation to write data onto signal Phase changes identify code Large numbers of codes can be generated Not all are suitable for navigation due to correlation properties Known as Phase Shift Keying (PSK)

Correlation Processing - Tone Signal Incoming Signal Stored Replica Reasonable Timing Detection Threshold Correlation Response

Correlation Processing - Wideband Signal Signal Perfect Match Replica Large Peak Very Accurate Timing Detection Threshold Response

Robust acoustic data telemetry Header wideband signal - correlation gives very low false alarm rate - hence noise immunity - very good timing sync Data content encoded using proprietary signals - auto compression of ASCII - Forward Error Correction gives error-free data - or no data Not a full modem implementation - inefficient for short packet sizes - introduces latency by using training data 5000m achieved at 25kHz IRS Wideband Telemetry Data Packet

Tsunameter - New Developments Enhanced pressure sensor measurement electronics and firmware - Continuous power to sensor - Continuous sampling of pressure (15 sec / sample) - NOAA Detection Algorithm applied to samples Additional memory card data back-up storage - 2 years into 128MB MMC card Lower Frequency band ~15kHz (Prevents clashes with MF LBL and USBL systems) 5000m rated housing, (7000m option)

Acoustic Study for NIOT Noise level at surface & seabed Transmission loss: - signal attenuation in vertical path - choice of frequency band 15kHz Off-vertical corrections for beam pattern Off-vertical analysis of ray-bending using water column profile data Equipment detection and transmit levels factory checked Sonar Equation gives the Operating Margin (db)

Q & A Head Office Sonardyne International Limited T. +44 (0) 1252 872288 Blackbushe Business Park F. +44 (0) 1252 876100 Yateley, Hampshire, GU46 6GD E. sales@sonardyne.com United Kingdom