Saturday, September 15, 2007

Expedition planning #5 : Marching Orders

It is now official: this Antarctic summer's expedition is on. We - my intrepid collaborator JY and I - received our marching orders last week.

They consist in a departure date (December 26th), a 40-page document containing information about our journey and about the two bases we will visit / sojourn at (Dumont d'Urville and Concordia), a list of clothing we will be issued with (some pretty cool warm stuff), and lots of medical forms for us and our doctors to fill in.

Next on our list - together with building / testing / fixing the equipment that must be shipped out by the end of the month - is getting doctors' and dentists' appointments to make sure we're physically good to go.

-----
Keep up to date with the latest developments at Sismordia - Seismology at Concordia

Friday, September 14, 2007

From Pietro Di Felice #3

Here is yet another message from Pietro di Felice (message orignally sent Sept 5th - my apologies for late posting). It has been pretty cold at Concordia lately, with temperatures going down to -80C.  Perfect temperature for an Antarctic sauna, don't you think? 

Miei cari amici,
finite le vacanze (sempre per chi le ha fatte ben inteso)?!?!?!

So che la calura a Roma e dintorni ancora  si fa sentire,  dovreste sentire che freschetto che fa qui. Malgrado l'arrivo del sole il mese di settembre è sempre il più freddo e le temperature raggiungono i record stagionali. Ieri l'altro abbiamo registrato il picco di -81.9°C senza vento, col vento si scende oltre i -100°......... I metereologi sono "fiduciosi" che si possa comunque scendere al di sotto queste soglie (sono pazzi questi metereologi).

Detto tra noi io non vedo l'ora di avere un pò più di caldo cosa che dovrebbe avvenire dalla fine del mese in poi. Comunque se continua così tentiamo di entrare nel "club 300"... che cos'è direte voi?!?!?!?? è una delle tante cose strambe "inventate" dagli americani che stanno qui al polo, più a sud di noi, nella stazione di South Pole esattamente al polo sud geografico.  Club 300, deriva dal fatto che il tutto va fatto quando la temperatura dell'aria scende al di sotto dei -80°C che nell'unità anglosassone del Fahrenheit è di - 300°, di qui il nome club 300.......... Vi terrò aggiornati!!!!!!

Insomma in parole povere tutto quello di cui si ha bisogno è una sauna........ e dove la prendi una sauna in Antartide?!?!?!? beh voi non ci crederete ma tutte le basi al Polo ne hanno una, per lo più sono baracche di legno non più grandi di 2 metri per 2 metri, dentro cui si ficca un braciere elettrico e lo si manda a "tutto gas"!!! anche da noi c'è, dall'esterno sembra, anzi è davvero una baracca di legno, e l'interno non è migliore, però funziona. Insomma, si porta la sauna a temperatura elevata, ci si infila dentro come in una normale sauna...... Poi, quando si è ben caldi, si indossano le scarpe e si esce nudi come mamma c'ha fatti e si fa un giro della base il più in fretta possibile.

Le giornate si vanno piano piano allungando, le ombre sul terreno invece si accorciano di giorno in giorno. I colori sono sempre accesi, l'arancio dell'alba si porta dietro tonalità giallo verdi e celi di un azzurro incontaminato (sempre che i fumi dei nostri della nostra centrale non decidano di sparpagliarsi a ventaglio sulle nostre zucche). La sera poi, verso le 18 il sole termina la sua corsa sul carro di Apollo e le tenebre tornano padroni del tempo e dello spazio intorno a noi. Ecco che allora miliardi di occhi lucenti appaiono e ci guardano dall'alto immobili. Gli astronomi in base allora iniziano a lavorare, gli ultimi mesi di fatica visto che poi verso l'inizio di ottobre, con l'avvicinarsi dell'ultimo tramonto le stelle smetteranno di comparire e loro andranno in "ferie".

[...]

A presto e buona giornata a tutti. Vi aspetto

Pietro polare


-----
Keep up to date with the latest developments at Sismordia - Seismology at Concordia

Thursday, September 13, 2007

Antarctic blog posts review #3

If you've been wondering why it's been so long since my last blog post review, I can give two reasons: not that many Antarctic posts, and not much free time for blogging (ok, I'll be honest, my main reason is the second one: I've been maxing out on work lately, trying to get the equipment needed for this summer's Antarctic campaign ready - more on that in a later post).

Here are two of my favourite recent posts from the nether regions of the world:

Escape from Station
Z-Doc does it again, with a beautifully crafted photo-post.  With the return of sunlight, the intrepid over-winterers now have a chance to get out and about.  And for those lucky enough to be living close to Emperor Penguin colonies, the photo opportunities are far from scarce, though not always easy (skidoos and the cold often do not agree too well).

The Bivvy
Just in case you were not convinced of the craziness of some of the guys and gals who chose to spend a year freezing their extremities off in Antarctica, come read how a group of crazies decided to sleep outside in -40 degrees... for fun.

-----
Keep up to date with the latest developments at http://sismordia.blogspot.com

Another major earthquake hits Indonesia

It never rains but it pours... nowhere is this more true than in Indonesia right now. Here is the USGS ShakeMap for another major quake in the region:



The local tsunami warning for this quake issued by PTWC is available here.

-----
Keep up to date with the latest developments at http://sismordia.blogspot.com

Powerful earthquakes hit Indonesia

Indonesia was hit yesterday (Wednesday) by one great (M8.4) and one major (M7.9) earthquakes, followed by a number of strong to moderate aftershocks. News reports about the quakes can be found all over the web, but also here, here, here and here.

The various tsunami warning centers, including the Pacific Tsunami Warning Center in Hawaii, reacted immediately, sending out first preliminary warnings then tsunami reports. Mike Dunford wrote a nice post about these tsunami warnings here.

Here are the ShakeMaps (earthquake intensity maps) published by the USGS for these two earthquakes, followed by the most up-to-date tsunami bulletin by the PTWC for the larger of the two events (the PTWC has issued a warning also for the second event, available here):






TSUNAMI BULLETIN NUMBER 005
PACIFIC TSUNAMI WARNING CENTER/NOAA/NWS
ISSUED AT 1505Z 12 SEP 2007

THIS BULLETIN IS FOR ALL AREAS OF THE INDIAN OCEAN.

... FINAL INDIAN-OCEAN-WIDE TSUNAMI WATCH ...

THIS THE FINAL TSUNAMI WATCH FOR

INDONESIA / AUSTRALIA / INDIA / SRI LANKA / THAILAND / UNITED KINGDOM / MALDIVES / MYANMAR / MALAYSIA / BANGLADESH / MAURITIUS / REUNION / SEYCHELLES / MADAGASCAR / SOMALIA / OMAN / PAKISTAN / IRAN / YEMEN / COMORES / CROZET ISLANDS / MOZAMBIQUE / KENYA / TANZANIA / KERGUELEN ISLANDS / SOUTH AFRICA / SINGAPORE

THIS BULLETIN IS ISSUED AS ADVICE TO GOVERNMENT AGENCIES. ONLY NATIONAL AND LOCAL GOVERNMENT AGENCIES HAVE THE AUTHORITY TO MAKE DECISIONS REGARDING THE OFFICIAL STATE OF ALERT IN THEIR AREA AND ANY ACTIONS TO BE TAKEN IN RESPONSE.

AN EARTHQUAKE HAS OCCURRED WITH THESE PRELIMINARY PARAMETERS

ORIGIN TIME - 1110Z 12 SEP 2007
COORDINATES - 4.5 SOUTH 101.3 EAST
LOCATION - SOUTHERN SUMATERA INDONESIA
MAGNITUDE - 8.2

MEASUREMENTS OR REPORTS OF TSUNAMI WAVE ACTIVITY

GAUGE LOCATION LAT LON TIME AMPL PER
------------------- ----- ------ ----- --------------- -----
SIBOLGA ID 1.7N 98.8E 1434Z 0.09M / 0.3FT 52MIN
PADANG ID 0.9S 100.4E 1348Z 0.98M / 3.2FT 34MIN
COCOS CC 12.1S 96.9E 1236Z 0.11M / 0.4FT 22MIN
DART 23401 8.9S 88.5E 1421Z 0.02M / 0.1FT 15MIN
LAT - LATITUDE (N-NORTH, S-SOUTH)
LON - LONGITUDE (E-EAST, W-WEST)
TIME - TIME OF THE MEASUREMENT (Z IS UTC IS GREENWICH TIME)
AMPL - TSUNAMI AMPLITUDE MEASURED RELATIVE TO NORMAL SEA LEVEL.
IT IS ...NOT... CREST-TO-TROUGH WAVE HEIGHT.
VALUES ARE GIVEN IN BOTH METERS(M) AND FEET(FT).
PER - PERIOD OF TIME IN MINUTES(MIN) FROM ONE WAVE TO THE NEXT.

EVALUATION

SEA LEVEL READINGS INDICATE A TSUNAMI WAS GENERATED. IT MAY HAVE BEEN DESTRUCTIVE ALONG COASTS NEAR THE EARTHQUAKE EPICENTER.

FOR THOSE AREAS - WHEN NO MAJOR WAVES HAVE OCCURRED FOR AT LEAST TWO HOURS AFTER THE ESTIMATED ARRIVAL TIME OR DAMAGING WAVES HAVE NOT OCCURRED FOR AT LEAST TWO HOURS THEN LOCAL AUTHORITIES CAN ASSUME THE THREAT IS PASSED. DANGER TO BOATS AND COASTAL STRUCTURES CAN CONTINUE FOR SEVERAL HOURS DUE TO RAPID CURRENTS. AS LOCAL CONDITIONS CAN CAUSE A WIDE VARIATION IN TSUNAMI WAVE ACTION THE ALL CLEAR DETERMINATION MUST BE MADE BY LOCAL AUTHORITIES.

BASED ON AVAILABLE DATA THIS CENTER DOES NOT EXPECT MORE WIDESPREAD DESTRUCTIVE EFFECT. HOWEVER ... DUE TO ONLY LIMITED SEA LEVEL DATA FROM THE REGION IT MAY NOT BE POSSIBLE FOR THIS CENTER TO RAPIDLY NOR ACCURATELY EVALUATE THE STRENGTH OF A TSUNAMI IF ONE HAS BEEN GENERATED.

ESTIMATED INITIAL TSUNAMI WAVE ARRIVAL TIMES AT FORECAST POINTS WITHIN THE WARNING AND WATCH AREAS ARE GIVEN BELOW. ACTUAL ARRIVAL TIMES MAY DIFFER AND THE INITIAL WAVE MAY NOT BE THE LARGEST. A TSUNAMI IS A SERIES OF WAVES AND THE TIME BETWEEN SUCCESSIVE WAVES CAN BE FIVE MINUTES TO ONE HOUR.

LOCATION FORECAST POINT COORDINATES ARRIVAL TIME
-------------------------------- ------------ ------------
INDONESIA BENGKULU 3.9S 102.0E 1123Z 12 SEP
SIBERUT 1.5S 98.7E 1203Z 12 SEP
PADANG 0.9S 100.1E 1214Z 12 SEP
BANDAR LAMPUNG 5.7S 105.3E 1242Z 12 SEP
SIMEULUE 2.5N 96.0E 1243Z 12 SEP
CILACAP 7.8S 108.9E 1307Z 12 SEP
BANDA ACEH 5.5N 95.1E 1329Z 12 SEP
BALI 8.7S 115.3E 1345Z 12 SEP
KUPANG 10.0S 123.4E 1453Z 12 SEP
BELAWAN 3.8N 99.0E 1703Z 12 SEP
AUSTRALIA CHRISTMAS IS 10.4S 105.4E 1220Z 12 SEP
COCOS ISLAND 12.1S 96.7E 1234Z 12 SEP
NORTH WEST CAPE 21.5S 113.9E 1429Z 12 SEP
CAPE INSPIRATIO 25.9S 113.0E 1526Z 12 SEP
CAPE LEVEQUE 16.1S 122.6E 1542Z 12 SEP
PERTH 32.0S 115.3E 1545Z 12 SEP
AUGUSTA 34.3S 114.7E 1559Z 12 SEP
GERALDTOWN 28.6S 114.3E 1603Z 12 SEP
ESPERANCE 34.0S 121.8E 1726Z 12 SEP
KINGSTON SOUTH 37.0S 139.4E 1906Z 12 SEP
EUCLA MOTEL 31.8S 128.9E 1934Z 12 SEP
DARWIN 12.1S 130.7E 1948Z 12 SEP
HEARD ISLAND 54.0S 73.5E 1955Z 12 SEP
HOBART 43.3S 147.6E 2015Z 12 SEP
INDIA GREAT NICOBAR 7.1N 93.6E 1338Z 12 SEP
LITTLE ANDAMAN 10.7N 92.3E 1421Z 12 SEP
PORT BLAIR 12.0N 92.5E 1440Z 12 SEP
NORTH ANDAMAN 13.3N 92.6E 1453Z 12 SEP
CHENNAI 13.4N 80.4E 1540Z 12 SEP
KAKINADA 17.2N 82.7E 1604Z 12 SEP
TRIVANDRUM 8.3N 76.9E 1608Z 12 SEP
BALESHWAR 21.6N 87.3E 1701Z 12 SEP
MANGALORE 13.3N 74.4E 1732Z 12 SEP
BOMBAY 18.8N 72.6E 2005Z 12 SEP
GULF OF KUTCH 22.7N 68.9E 2019Z 12 SEP
SRI LANKA DONDRA HEAD 5.8N 80.5E 1447Z 12 SEP
TRINCOMALEE 8.7N 81.3E 1502Z 12 SEP
COLOMBO 6.9N 79.8E 1515Z 12 SEP
JAFFNA 9.9N 80.0E 1625Z 12 SEP
THAILAND PHUKET 8.0N 98.2E 1508Z 12 SEP
KO PHRA THONG 9.1N 98.2E 1554Z 12 SEP
KO TARUTAO 6.6N 99.6E 1626Z 12 SEP
UNITED KINGDOM DIEGO GARCIA 7.3S 72.4E 1526Z 12 SEP
MALDIVES GAN 0.6S 73.2E 1528Z 12 SEP
MALE 4.2N 73.6E 1544Z 12 SEP
MINICOV 8.3N 73.0E 1614Z 12 SEP
MYANMAR PYINKAYAING 15.8N 94.2E 1537Z 12 SEP
CHEDUBA ISLAND 18.9N 93.4E 1554Z 12 SEP
SITTWE 20.0N 92.9E 1629Z 12 SEP
MERGUI 12.8N 98.4E 1647Z 12 SEP
YANGON 16.2N 96.5E 1713Z 12 SEP
MALAYSIA GEORGETOWN 5.4N 100.1E 1704Z 12 SEP
PORT DICKSON 2.5N 101.7E 2048Z 12 SEP
BANGLADESH CHITTAGONG 22.5N 91.2E 1801Z 12 SEP
MAURITIUS PORT LOUIS 20.0S 57.3E 1803Z 12 SEP
REUNION ST DENIS 20.8S 55.2E 1820Z 12 SEP
SEYCHELLES VICTORIA 4.5S 55.6E 1847Z 12 SEP
MADAGASCAR TOAMASINA 17.8S 49.8E 1900Z 12 SEP
ANTSIRANANA 12.1S 49.5E 1905Z 12 SEP
MANAKARA 22.2S 48.2E 1919Z 12 SEP
CAP STE MARIE 25.8S 45.2E 2009Z 12 SEP
MAHAJANGA 15.4S 46.2E 2009Z 12 SEP
TOLIARA 23.4S 43.6E 2034Z 12 SEP
SOMALIA HILALAYA 6.5N 49.2E 1922Z 12 SEP
CAPE GUARO 11.9N 51.4E 1933Z 12 SEP
MOGADISHU 2.0N 45.5E 1938Z 12 SEP
KAAMBOONI 1.5S 41.9E 2004Z 12 SEP
OMAN SALALAH 17.0N 54.2E 1930Z 12 SEP
DUQM 19.7N 57.8E 1939Z 12 SEP
MUSCAT 23.9N 58.6E 1943Z 12 SEP
PAKISTAN GWADAR 25.1N 62.4E 1937Z 12 SEP
KARACHI 24.7N 66.9E 2031Z 12 SEP
IRAN GAVATER 25.0N 61.3E 1943Z 12 SEP
YEMEN AL MUKALLA 14.5N 49.2E 2003Z 12 SEP
ADEN 13.0N 45.2E 2100Z 12 SEP
COMORES MORONI 11.6S 43.3E 2006Z 12 SEP
CROZET ISLANDS CROZET ISLANDS 46.4S 51.8E 2009Z 12 SEP
MOZAMBIQUE CABO DELGADO 10.7S 40.7E 2034Z 12 SEP
ANGOCHE 15.5S 40.8E 2044Z 12 SEP
QUELIMANE 18.0S 37.1E 2213Z 12 SEP
MAPUTO 25.9S 32.8E 2218Z 12 SEP
BEIRA 19.9S 35.1E 2246Z 12 SEP
KENYA MOMBASA 4.0S 39.7E 2039Z 12 SEP
TANZANIA LINDI 9.8S 39.9E 2039Z 12 SEP
DAR ES SALAAM 6.7S 39.4E 2047Z 12 SEP
KERGUELEN ISLAN PORT AUX FRANCA 49.0S 69.2E 2049Z 12 SEP
SOUTH AFRICA PRINCE EDWARD I 46.6S 37.6E 2146Z 12 SEP
DURBAN 29.8S 31.2E 2205Z 12 SEP
PORT ELIZABETH 33.9S 25.8E 2256Z 12 SEP
CAPE TOWN 34.1S 18.0E 2359Z 12 SEP
SINGAPORE SINGAPORE 1.2N 103.8E 0048Z 13 SEP

THE JAPAN METEOROLOGICAL AGENCY MAY ISSUE ADDITIONAL INFORMATION FOR THIS EVENT. IN THE CASE OF CONFLICTING INFORMATION...THE MORE CONSERVATIVE INFORMATION SHOULD BE USED FOR SAFETY.


-----
Keep up to date with the latest developments at http://sismordia.blogspot.com

Wednesday, September 12, 2007

Earthquake magnitude or earthquake intensity?

As a seismologist, I am pretty used to dealing with the dual concepts of earthquake magnitude and earthquake intensity. Magnitude quantifies the energy released by the earthquake. Intensity quantifies the ground shaking at a particular location. These concepts are so bread-and-butter to me that I sometimes forget how many people get them confused when listening to reports of earthquakes on the news media.

Nowadays, news media usually get their reporting pretty straight, thanks also to the improved communication coming out of seismological laboratories around the world. Guidelines and explanations are routinely offered now to the media whenever an earthquake occurs. Here is an excerpt from what the USGS puts online after every major earthquake:

Magnitude is the number (for example, 7.1) that represents the energy released in an earthquake; a single number representing magnitude is assigned to each earthquake. Intensity, on the other hand, is a measure of how the ground shook at a particular site. So, while an earthquake has one magnitude and one epicenter, it produces a range of ground shaking levels at sites throughout the region. These different intensities depend on distance from the earthquake, the rock and soil conditions at geographical sites, and variations in the propagation of seismic waves from the earthquake due to complexities in the structure of the Earth's crust.
Earthquake intensity is estimated both from instrumental records and from the reports of people who have felt the earthquake.  It is often reported in the form of a map, showing intensity as a function of position.   You can often report feeling an earthquake by filling in an online form (in the US these forms are provided by the USGS, in France they are provided by the BCSF). Intensity values are given using the following scale, the Modified Mercalli Intensity Scale:

I  -  People do not feel any earth movement.

II  -  Felt by persons at rest, on upper floors of tall buildings

III   -  Felt by people indoors. Hanging objects swing back and forth. Vibration from the earthquake may seem like the passing of light trucks. May not be recognized as an earthquake.

IV   -  Hanging objects swing. Vibration may seem like the passing of heavy trucks or a jolt, like a heavy ball striking the walls. Parked vehicles may rock noticeably. Windows, dishes, doors may rattle and glasses clink. In the upper range of IV, walls of wood frame buildings may creak.

V  -  Almost everyone feels movement whether inside or outdoors. Sleeping people are awakened. Liquids in containers are disturbed; some are spilled. Small unstable objects are displaced or overturned. Doors swing, close, or open. Shutters, pictures on the wall move.

VI  -  Felt by all; some are frightened and take cover. People have difficulty walking due to motion. Objects fall from shelves and dishes, glassware and ceramics may be broken. Pictures fall off walls. Furniture moves or is overturned. Weak plaster and masonry cracked. Damage slight in poorly constructed buildings. Trees, bushes shaken visibly or are heard rustling.

VII   -   People have difficulty standing. Drivers on the road feel their cars shaking. Furniture may be overturned and broken. Loose bricks fall from buildings and masonry walls and cracks in plaster and masonry may appear. Weak chimneys may break at the roofline. Damage is slight to moderate in well-built structures; considerable in poorly constructed buildings and facilities.

VIII   -   Drivers have trouble steering. Tall structures such as towers, monuments and chimneys may twist and fall. Wood frame houses that
are not bolted to their foundations may shift and sustain serious damage. Damage is slight to moderate in well-constructed buildings, considerable in poorly constructed buildings. Branches are broken and fall from trees. Changes occur in flow or temperature of springs and wells. Cracks appear in wet ground and on steep slopes.

IX  -   Masonry structures and poorly constructed buildings suffer serious damage or collapse. Frame structures, if not bolted, shift off foundations. Serious damage to reservoirs. Underground pipes broken. Conspicuous cracks in the ground. In alluvial areas, sand and mud ejected and sand craters are formed.

X  -   Most masonry and frame structures destroyed along with their foundations. Some well-built wooden structures and bridges are destroyed. Serious damage to dams, dikes, and embankments. Large landslides occur. Water thrown on the banks of canals, rivers and lakes. Sand and mud shift horizontally on beaches and flat land. Rails bent.

Monday, September 10, 2007

Historical seismometers #3 - Ewing-Press

Welcome to the third post in my series on historical seismometers, featuring my favorite instruments from the Strasbourg Seismology Museum. After entries on the Wiechert and Galitzin seismometers, here is a post on the Ewing-Press.


Like the Galiztin, the Ewing/Press [photo credits Michel Dufloux] is an electromagnetic seismometer combined with a galvanometer. It's natural period is modifiable up to 30s. It is a long-period instrument, well adapted to recording surface waves, and was used in the first global seismic network, the WWSSN.

The instrument in our museum was made in 1953 at the Lamont Geological Observatory of Columbia. It was in use in Strasbourg from 1963 to 1975. My favorite feature is the glass ball on the vertical component (in the photo), which eliminates the effect of pressure variations on the seismic signal.

-----
Keep up to date with the latest developments at http://sismordia.blogspot.com