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Tsunami Detection SystemNick Street, Project EngineerDavid Mould, Presenter

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Agenda

1. Need for Tsunami Detection System2. System Overview3. Tsunami Detection System requirements4. Seabed Unit - Tsunameter5. Surface Unit - Transceiver6. Satellite Modem Link7. Data Examples8. Acoustic telemetry overview 9. Q&A

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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.

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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.

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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

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Tsunami Detection System Requirements

• Pressure sensor• Detection Algorithm• Acoustic Link• Long battery life• Release mechanism• Floatation• Satellite modem

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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.

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Tsunami Detection System

1. Need for Tsunami Detection System2. System Overview3. Tsunami Detection System requirements4. Seabed Unit - Tsunameter5. Surface Unit - Transceiver6. Satellite Modem Link7. Data Examples8. Acoustic Telemetry Overview 9. Q&A

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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

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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

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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

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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

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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

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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

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Tsunameter – Deployment in the Bay of Bengal

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Tsunami Detection System

1. Need for Tsunami Detection System2. System Overview3. Tsunami Detection System requirements4. Seabed Unit - Tsunameter5. Surface Unit - Transceiver6. Satellite Modem Link7. Data Examples8. Acoustic Telemetry Overview 9. Q&A

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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

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Tsunami Detection System

1. Need for Tsunami Detection System2. System Overview3. Tsunami Detection System requirements4. Seabed Unit - Tsunameter5. Surface Unit - Transceiver6. Satellite Modem Link7. Data Examples8. Acoustic Telemetry Overview 9. Q&A

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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

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Tsunami Detection System

1. Need for Tsunami Detection System2. System Overview3. Tsunami Detection System requirements4. Seabed Unit - Tsunameter5. Surface Unit - Transceiver6. Satellite Modem7. Data Examples8. Acoustic Telemetry Overview 9. Q&A

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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

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,

YMDHMS Type 1 (Hourly) P1 P2 P3 P4Pressure Log Status

Tpdr ID F/W Version % Used Battery Alarm Battery On Tilt° Temperature

Up to 128 ASCII characters for customer defined message

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Data Example - Hourly Pressure Messages

Acoustic data hourly message, data points every 15 minutes

34000

35000

36000

37000

38000

39000

40000

41000

42000

18:00 00:00 06:00 12:00 18:00 00:00

Date Time

Raw

abs

. pre

ssur

e (1

0Pa)

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Logged Data Analysis

Simulated Event: measured vs predicted, data from memory card (Difference rebased to 142600)

142000

142100

142200

142300

142400

142500

142600

142700

142800

142900

143000

143100

143200

143300

143400

143500

143600

143700

143800

143900

144000

09:20 09:30 09:40 09:50 10:00

Raw

abs

pre

ssur

e (P

a)

MeasuredPredictedDiff (C-O) detection point

Vertical scale: 1 div ~ 1cm

detection threshold

3 cm

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Data Recovery

t0 t180

Event mode:1x Type 2 message containing 4 x 15s consecutive readings 2 before & 2 during Event)

Time (minutes)

Extended reporting mode:36x Type 3 messages containing10 readings, 30s apart (sent every 5 minutes)

t60 t240

Standard mode:Type 1 message containing 4 readings averaged over 15 minutes sent every hour

t120t-60

Tsunameter: Full Event Cycle

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Event - Data Recovery

Tsunameter: records telemetered during Event

t0

Event mode:4 x 15s readings

Time (minutes)

Extended reporting mode:36 x 10 x alternate 15s readings

t2t-1t-2 t3

A single raw pressure valueOne reading made every 15 seconds

One acoustic message

Key:t1 t5t4 t6 t7 t8 t9 t10 t11 t12

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Acoustic Data from Plymouth Trial – 30 Metres

Tsunami C5 acoustic data: Plymouth 18 - 21 Sept sent via SMS(vertical scale ˜ 1m/div)

34000

35000

36000

37000

38000

39000

40000

41000

42000

18/09/2006 19/09/2006 20/09/2006 21/09/2006 22/09/2006 23/09/2006

Raw

abs

pre

ssur

e (1

0Pa)

Event detection at 01:08 starts rapid data telemetry for 180 minutes

Another detection at 07:07

Unit recovered to surface

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Sea Trial Data – 600 Metres

Sonardyne sea trial - 600m

608600

608700

608800

608900

609000

609100

609200

609300

609400

609500

609600

609700

609800

609900

610000

610100

610200

16/02/2007 17/02/2007 18/02/2007 19/02/2007 20/02/2007 21/02/2007

Abs

olut

e pr

essu

re (1

0Pa

~mm

)

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NIOT Tsunami Buoy Locations

Buoy TB10 which sent the following data

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NIOT Battery Life Test

Sonardyne data: Nicobar earthquake 25/07/07Station: TB10 - 7 deg 1'N 87 deg 4'E Source: 7.08N 92.59E Magnitude 6.2

3851000

3851100

3851200

3851300

3851400

3851500

3851600

3851700

3851800

3851900

3852000

15/07/2007 17/07/2007 19/07/2007 21/07/2007 23/07/2007 25/07/2007 27/07/2007

Abs

pre

ssur

e (1

mm

~ 1

0 Pa

)

Vertical scale ~10cm/div

Real event caused NIOT to be concerned about battery life

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The Event – Two Hours Before

Sonardyne data: Nicobar earthquake 25/07/07Station: TB10 - 7 deg 1'N 87 deg 4'E Source: 7.08N 92.59E Magnitude 6.2

3851560

3851570

3851580

3851590

3851600

3851610

3851620

3851630

3851640

3851650

3851660

3851670

3851680

3851690

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

Abs

pre

ssur

e (1

mm

~ 1

0 Pa

)

Vertical scale ~1cm/div

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, ½and ¾ hour records are not sent

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The Event - Post Event Data

Sonardyne data: Nicobar earthquake 25/07/07Station: TB10 - 7 deg 1'N 87 deg 4'E Source: 7.08N 92.59E Magnitude 6.2

3851550

3851560

3851570

3851580

3851590

3851600

3851610

3851620

3851630

3851640

3851650

3851660

3851670

3851680

3851690

3851700

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

Abs

pre

ssur

e (1

mm

~ 1

0 P

a)

Vert. scale: ~1cm/div

Data points passed on by NIOT satellite phone system

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The Event – National Media Coverage

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Tsunami Detection System - Requirements

1. Need for Tsunami Detection System2. System Overview3. Tsunami Detection System requirements4. Seabed Unit - Tsunameter5. Surface unit - Transceiver6. Satellite Modem Link7. Data Examples8. Acoustic Telemetry Overview 9. Q&A

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A Tone signal

• Single Frequency

• No modulation

• Defined duration

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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)

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Correlation Processing - Tone Signal

Incoming Signal

Stored Replica

DetectionThreshold

Correlation Response

ReasonableTiming

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Correlation Processing - Wideband Signal

Signal

Replica

Response

LargePeak

VeryAccurateTiming

DetectionThreshold

Perfect Match

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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

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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)

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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)

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Q & A

Head Office

Sonardyne International Limited T. +44 (0) 1252 872288Blackbushe Business Park F. +44 (0) 1252 876100Yateley, Hampshire, GU46 6GD E. sales@sonardyne.comUnited Kingdom www.sonardyne.com