Title:

CTBT APPLICATIONS IN COMOROS Ms. Mariama MADI

Earth Science Field, Seismic Analyst National Data Centre, Volcano Observatory Collaborator, CNDRS

(National Centre of Scientific Research and Documentation), Moroni-COMOROS

Email: mariabdjul@hotmail.com

Abstract:

Civil and scientific uses of CTBT data and products in Comoros are a reality considering natural

hazards and catastrophes related to the "Karthala" volcano activities in Comoros, which for some

years of eruptions, remain the major source of important releases of ashes and gases. The oceanic

aspect is also affected by the fact that the 2004 Indonesian Tsunami is recorded with up to 6.9

run ups in several coastal areas in Comoros.

Through the CTBT International Monitoring System, recent events (2010, 2013 etc.) were

clearly recorded.

Key words:

Seismic Source: Karthala (Active volcano), Oceanic hazards: Tsunami effects, Volcano hazards: infrasound and

Seismic effects

1. Introduction

Karthala Volcano, relevant Source of Seismic

and Infrasound hazards in the Comoro Islands.

Without any Hydro-acoustic Station in

the vicinity of Comoro-Islands, still the Hydro-

acoustic Technology shows a global Interest,

while NDCs can have access to the IDC Data

and Products.

this access allows the scientific community to

understand further the aspect of the oceanic

activities, the source, the word areas affected, as

the case during the 2004 Indonesian tsunami (up

to 6.9 m run-ups in several coastal areas in

Comoro Islands).

These following points raise the interest

of Subject

-2004 Indonesian Tsunami

-Karthala Volcano: as an Infrasound source

(Fig.1)

Corresponding Author: Ms. Mariama Madi, Seismic

Analyst, main Research fields: CTBT Applications in

COMOROS. Email: mariabdjul@hotmail.com

-Karthala Volcano: major Seismic Identification

(Fig.1)

Fig.1: National Data Centre, Seismic Support data to

the Volcano Observatory, Relevant CTBT Functions in

Comoros [1]

2. Geological Background of Comoro-

Islands

Chain of 4 volcanic islands located at

the northern end of the Mozambique Channel

separating Madagascar from southeastern Africa.

Hawaiian volcanoes Morphology as for:

-Grand Comore (1148km2), hosting the active

“Karthala volcano” (rising to 2361 m .al)

-Moheli (211km2; 790m al.), dated to 2,2Ma

-Anjouan (424km2; 1595m al.), dated to 1.5Ma

-Mayotte (374 km2; 660m al.), dated to ~5.4 Ma

(Hajash and Armstrong, 1972; Emerick and

Duncan, 1982) [1].

In another aspect of these studies, the

rate of migration of volcano in the Comoros

would require excessive rates of spreading

across the African Rift from global study of the

motion of the young hotspot chains over the

mantle conducted by Gripp and Gordon (2002)

[2].

Fig.2: Comoro-Islands, located at the northern end of

the Mozambique Channel separating Madagascar from

southeastern Africa. From the recent to the old one, it

constituted by Grande-Comore (Ngazidja), Anjouan

(Ndzouani), Moheli (Mwali) and Mayotte (Maore). [4]

Karthala volcano remaining the

important seismic and infrasound source in the

Island, hosts intra-caldera Units as following:

-Olivine basalts (almost in the entire Island)

-Basalts scoria

-Thrown blocks

-Lava flows (19th, 20

th centuries)

-Undated Lava flows

- Etc.

Caldeira zone of Karthala (Grande-Comore)

Fig.3: Geological map [5] of the intra-caldeira units

of karthala volcano (Grande-Comore). As the Biggest

Islands, the Recent and the one which hosts the active

Volcano, it was important to mention the Units within

the Crater as intra-caldeira Units.

3. Event Source characteristics

significant to CTBT Applications

Comoro-Islands are exposed to several

Naturals Hazards simultaneous to the entire

world affected. The country may assist to

Tsunami, radioactive, infrasound and seismic

effects, therefore, dealing with the

Comprehensive Nuclear Test Ban Treaty

Organization (CTBTO) as signatory member

state, the country earns Scientific and

Technological Supports through: Training

Geographic situation

Secondary crater

Principal Crater

Courses, Use of IMS (International Monitoring

Station) Data and IDC (International Data

Centre) Products, Capacity Building System

(Technical support), National Data Centre

establishment and other Researches expected

to ameliorate the scientific aspect of NDCs.

During the Science and Technology

Conference 2013, I preferred as subject field to

introduce the continental, oceanic (tsunami,

run-ups) Seismic aspect and the effects related

to, by including the “2004 Indian ocean

tsunami, Comoro-Islands”, “Infrasound Source,

volcanic ash layer from 2005 Phreato-

magmatic eruption in Gde-Comore”, and

“Seismic Source, Karthala volcano”.

Fig.4: the 2004 Indian Ocean and global tsunami

affected Comoros up to 6.9 run-ups along the coast

lines. Volcanic ash, Blocks, and gases are released

from the two phreatic eruptions in 2005. And two

among important seismic activities are recorded by

the IDC through CTBT International Monitoring

System in Comoro-Islands. [6]

4. 2004 Indonesian Tsunami:

Considerable Run-ups around Islands

a- SUMATRA-ANDAMAN Tsunami surveys in

Comoro Islands (South African Journal of

Geology “Book reference”.) [7]

Fig.5: The 2004 SUMATRA-ANDAMAN Tsunami

surveys in Comoro Islands conducted in 2006 and 2007,

reveled significant records of Run-up in almost 35 areas.

[8]

b- “NDC” National Data Centre Comoros

and Asians Experts Survey in Grande-

Comore in 10 February 2011. The idea of survey was to evaluate the disaster

caused by the Indian Ocean tsunami in

Comoros as part of the Indian Ocean affected

zones. The survey was based on villager’s

Testimony; therefore, waves reached homes

implemented nearby coast lines, and hopefully

without any casualties. In Fact, after the 2006

and 2007 survey (Fig:5), we decided to reach

affected areas and people in order to evaluate

the damage, by choosing two villages in the

North areas most affected of Gde-Comore,

which are: “Bangoua-kouni” (11022’S

43022’E), and “Bouni” (11028’S 43023’E).

Fig.6: Bangoua-kouni: we surveyed two points, and

evaluated an average run-up of 2.52 m. Bouni: pointed

5 sites, we recorded 5.8m in ‘Bouni.1’ and 6.7m in

‘Bouni.2’. [9]

c- Field information summary: “Bangoua-

kouni”

- Record of Run-up: 2.52m

- Flat area along the coast line

- Sea wall height about 2.5m above sea

level

- Arriving of tsunami at 4:30-5:00 am

(Local time)

- Inundation line reach up to 50m distant

inland

- Inundation period was 3 hours before

retreating to the see

- First wave was the biggest and caused

inundation

d- Field information summary: “Bouni”

- Record of Run-up: 6-7m

- High slope area (hilly) along coast line

- Sea wall height about 3.0m above sea

level

- Arriving of tsunami at 4:30-5:00 am

(Local time)

- Inundation continued until 8:00-9:00 am

- None of the wave overtopping across

sea wall after 2004 tsunami

- First wave was the biggest and caused

inundation

5. Karthala Volcano: as an infrasound

source

Fi

Fig.7: relating to the CTBT official Infrasound Source

images, the active volcano in Grande-Comore is one

source evident causing during explosive eruption

considerable releases of gas particle and volcanic ashes

in Comoros.

a- Explosive eruptions in 2005:

Volcanic activities:

Successive seismic crises two years before are

followed by two important explosive eruptions

occurred in the “Principal Crater” (Fig: 3).

The 16 April and 25 November 2005 are

phreato-magmatic phases:

•Phase1: Interaction magma-water

•Phase2: explosive phase with enormous

quantity of ashes released into the atmosphere + large blocks ejected

•Phase3: lava inside the crater replaced the

initial water

b- Eruption Results and Impacts:

Fig.8: the ‘After eruptions’ Damage and environmental

impacts

- Emission of steam into the atmosphere

- Considerable amounts of ash released

many days after

- Gas particle emissions: H2O, CO2, CO

(1%), and other undefined particles.

- However, Severe breathing problems in

the vicinity of Karthala

- Almost 5m accumulation mud in many

areas after rain

- Plants, water resources,... also affected

- …

6- Karthala Volcano: Major Seismic

Identification Source

For decades Karthala has been the

“Home” of consistence volcanic activities. From

this issue the Volcano observatory was seeing

imperative to be installed in 1989 (Franco-

Comorian Cooperation) in terms of following

the evolution of its seismic background and the

aspect of eruptions in order to settle a sort of

volcanic disaster warming in Grande-Comore.

But in the present time, still the initiative needs

support for diverse reasons in terms of getting

accurate results and Data, receiving suspicious

volcanic activities and be “hands in hands” with

the ongoing technology.

As evident and most of time, seismic

activities (source: volcano) are natural and

physical steps to volcanic eruptions preceded by

‘Pressure-Temperature’ mechanisms.

During two centuries, Grande-Comore

has been shaken by numerous magmatic,

phreatic, and phreato-magmatic eruptions which

caused casualties (1903 and 1904) (Fig: 9),

affected the environment in general and caused

material damages.

Year Dates Location Type of eruption Surface covered (10

6 m

2)

Volume of magma estimated (10

6 m

3)

Seismicity felt

Damages

2007 13 January Secondary crater Magmatic (Summit) YES

2006 28 May Principal Crater Magmatic (Summit) -

2005 25 November Principal Crater Phreatio-magmatic -

2005 16 April Principal Crater Phreatio-magmatic -

1991 11 July Principal Crater Phreatic - No Magma YES YES

1977 5 - 10 April South-West Flank Magmatic eccentric 1.8 10.8 YES YES

1972 8 Sep - 5 October Caldeira Magmatic (Summit) 2.5 12 - -

1965 12 July Caldeira and Secondary Crater

Magmatic (Summit) 0.05 0.15 - -

1952 10- 14 February Principal Crater Magmatic (Summit) - - - -

1948 22 April to 4 May Secondary Crater Magmatic (Summit)

1948 13- 16 June Principal Crater Magmatic (Summit) and Phreatio-

magmatic

16 6 YES YES

1918 11 to 13 August North Rift zone Lateral-Magmatic 2.7 10 YES -

1918 25 - 26 August Principal Crater Phreatic 25 No Magma YES YES

1904 25 February to April North Rift zone Lateral-Magmatic 11 44 YES YES, one person

1903 - South-East Rift zone

Gas Emissions - - - YES, 17 persons

1880 - South-East Rift zone

Lateral-Magmatic 2.4 10 YES YES

1876 - South-East Rift zone

Lateral-Magmatic 4 17 - -

1872 - North Rift zone Lateral-Magmatic 1.6 7.2 - -

1860 December South-East Rift zone

Lateral-magmatic 5.5 30 - -

1859 - Rift-zone Lateral-magmatic 3.9 20 - -

1858 - Caldeira and Rift-zone

Lateral-magmatic 12.5 63 - -

1857 - South-East Rift zone and Caldeira

Lateral-magmatic 10 56 - YES

1848 - South-West Flank Eccentric Magmatic 3 16 - -

1830 - - Magmatic - - - -

1828 - - Magmatic - - - -

1821 - - Magmatic - - - -

1814 - - Magmatic - - - -

1808 - - Magmatic - - - -

Table: Chronology of Karthala Volcano Eruptions

Fig.9: Archives of Karthala volcano eruptions (1808 – 2007). [10]

In 2005 Phreatic and phreato-magmatic

eruptions were preceded by considerable

volcanic crises during two years. [11]

Fig.10: In 2003, almost two months (October- December)

separated two intensive magma activities. One year

after (December 2004) the 3rd major crisis took place

within two years (2003-2004). The 16 April 2005

explosive eruption occurred in the Principle crater of

Karthala.

6-1. Data acquisition: Volcano

observatory

Still the acquisition system “Earthworm”

considered as “old” software is being used.

Struggling access and Data analyses, One of the

big issues of the observatory is getting one the

software using by observatories in the worlds.

2 types of acquisition:

- Continuous Data

“Small” events (~ Mg 1, 1.5, 2 ~) saved as for:

Seismic background and for big (~Mg 4~)

events analyses, or for other volcanic-seismic Research purposes, etc.

- Trigger Data

“Big” Events (≥ Mg 4): These data are

considered to be analyzed for the Event location.

6-2. National Data Centre

This NDC as IDC (International Data

Centre) relevant CTBT function is playing a

major role of getting International Monitoring

System (IMS) Data and Products. The access

and analyzing of international, regional and local

seismic Data is a proof of being a tremendous

and Relevant for controlling both the oceanic

aspect ( earthquakes, understand tsunami

effects…) of the Comoro-Islands and the

continental aspects (seismic-volcanic,

earthquakes, …) of Grande-Comore itself.

However, what the National Data Centre

brings to the seismic natural events in Comoros

and the Seismic Events from the Volcano

activities in Grand-Comoro Island?

- Two among important seismic events in

the North part of Comoro Islands, recorded by

the International Data Centre ‘IDC’ in Vienna,

were out of the Observatory Control:

Region: Northwest of Madagascar,

COMOROS:

Event no1: Date: 14 October 2010.

Time: 10:03:33.9, Latitude: 10.28S, Lon: 42.81E

Magnitude mb: 4.5

Event no2: Date: 20 march 2013.

Time: 05:21:56.8, Lat: 11.73S Lon: 42.38E

Magnitude mb: 4.2 (Source: IDC secure website,

IMS Data) [12]

Event no1: Event Analysis:

“National Data Centre”

Fig.11: this image resumes the steps of analysis using

“Geotool” software, design for NDC Analysis purposes.

BOSA (S. Africa), KMBO (Kenya), ATD (Djibouti),

AKTO (Kazakhstan), are some of the stations recording

the Event. After getting the output, waveforms are

filtered to detect clear signals, in order to pick arrivals

(Pg, Lg, Pn, Sn, P, S … etc) with which the Location is

possible.

Event location

Fig.12: the location shows a source point on Comoros,

but accurately the zooming illustrated the exact source

of the event which is not right on the continental area,

but in a distance of ~130 km from the crater to a point

in the ocean. The National Data Centre located the

Event by: Latitude: -11.36 S, Longitude: 42.78 E, Depth:

11, Time: 2010 Oct 14 at 10:03:31, Magnitude: 4.8

Event no2: Event analysis

Fig.13: this Regional event is the recent one in the

northwest oceanic region of Madagascar (COMOROS)

in 2013. KMBO (Kenya), OPO, are two among the

stations recording the event, where Pn, Sn arrivals are

clearly picked. During analysis picking phases is the

important step of locating event with much

concentration. Otherwise an arrival picked by error

brings the event in another side of the Globe.

Event Location

Fig.14: As for the 1rst location, it was compulsory to

know exactly the source of event, while the location on

the map still appears like on the land. But relay on

Google measurement we recorded a distance of almost

~80 km from the Karthala crater to the source. This

determined distance was possible from the geographical

coordinates of the event given by the CTBT SEL1

automatic recorded Data products. From this analysis,

the NDC located the Event by: Latitude: -11.86,

Longitude: 42.19, Depth: 0.0000, Time: 2013 march 20

at 05:21:55, Magnitude: 3.99 to 4

Conclusion

Comoro Islands is geographically a

strategic area of oceanic natural activities in

terms of earthquakes and tsunami in the Indian

Ocean. Geologically complex, the country

composed by four Islands, Between Mayotte the

old one (~5.4 ma apparition) eroded and

surrounded by a nearly continuous coral reef

averaging 5 km in width (Ref. South African

Journal of Geology Book: Page 344), and

Grand-Comore the youngest hosting the active

Volcano (Karthala, altitude: 2360 m) in

Comoros.

The explosive aspect of eruptions (Gas

particles, ashes, steam, etc...) accelerates the

existence of infrasound source that Karthala

volcano remains the 1rst cause in the country.

And as evident, it (explosive eruption) selected

by CTBT as one of the Infrasound sources

within the International Monitoring System, and

for further research purposes.

For the Seismic aspect which is the

basic of our research in this subject, after

comparing activities at the volcano observatory

to the National Data Centre ’NDC’ (CTBT

related functions), we realized that:

-Seismic events from “few” kilometers of the

sea areas surrounding the Islands are not

recorded by the Volcano Observatory: In fact,

from this issue the National Data Centre is

playing a tremendous role as CTBT Relevant

functions in the country in terms of Seismic

Event analyses with much confidence receiving

International Data and Products from the

International Data Centre ‘IDC’ by the IMS.

-Comparison of the NDC Analysis results to the

IDC Experts analyses.

-And etc…

From these Points, the purpose of identifying

characteristics of Oceanic and Continental

events in Comoros is for Civil and Scientific

uses, but also to enhance through our countries

as member states the CTBT Treaty compliance

for a secured world.

Acknowledgements:

-The Comprehensive nuclear Test-Ban Treaty

Organization: CTBTO

-The ‘NDC’ National Data Centre-COMOROS

-The Volcano observatory, CNDRS, Moroni-

Comoros

References

[1] Fig: 1:“National Data Centre, seismic support data

support to the Volcano observatory, Relevant CTBT

Functions in Comoros”, designed by the Author Ms.

Mariama MADI, National Data Centre, CNDRS, Moroni-

Comoros.

[2] Mayotte Island dated at ~5.4 Ma (Hajash and

Armstrong, 1972; Emerick and Duncan, 1982), “South

African Journal of Geology” Page: 344

[3] Global study of the motion of young hotspot chains

over the mantle (Gripp and Gordon), “South African

Journal of Geology” Page: 344

[4] Fig.2: Google earth and satellite images joined and

designed by the Author Ms. Mariama MADI, National Data

Centre, CNDRS, Moroni-Comoros.

[5] “Volcan0-tectonic” Map of the Grande-Comore by

Patrick Bachelery and Jean Coudray, Earth Science

Department, University of La Reunion, 1993.

[6] Fig.4: Designed by Author Ms. Mariama MADI,

National Data Centre, CNDRS, Moroni-Comoros.

[7] 2004 Sumatra-Andaman Tsunami Surveys in Comoro-

Islands…., “South African Journal of Geology” Page: 344

[8] Fig.5: Google earth images and South African Journal

of Geology Data joined and designed by the Author Ms.

Mariama MADI, National Data Centre, CNDRS, Moroni-

Comoros.

[9] Fig.6: Product of survey by the Team, image designed

by the Author Ms. Mariama MADI, National Data Centre,

CNDRS, Moroni-Comoros.

[10] Chronology of Karthala volcano eruptions, Volcano

Observatory, CNDRS (National Centre of Sciences

Research and Documentation), Moroni-Comoros.

[11] Seismic events (2003-2005) recording, Volcano

Observatory, CNDRS (National Centre of Sciences

Research and Documentation), Moroni-Comoros.

[12] 10 October 2010, 20 march 2013 events from SEL1

automatic Data, International Data Centre Secure website,

Vienna-Austria.