Darjeeling

Posted on November 27, 2011 by marcia

Earthquake induced landslides in the Sikkim-Darjeeling Himalayas

Last update: November 25, 2011 at 7:37 pm by By Armand Vervaeck and James Daniell

Aftermath of the 18th September 2011 Sikkim earthquake

By : Indranil Chakraborty, Dr. Saibal Ghosh, Debasish Bhattacharya & Anjan Bora, Engineering Geology Division, Geological Survey of India, Eastern Region, Kolkata

Introduction

According to the Indian Meteorological Department (IMD) 1, a strong earthquake of Magnitude M: 6.8 shook Sikkim and Darjeeling areas of India and adjoining Nepal at 18.11 hours IST on 18th September 2011 with its epicenter (27.7oN, 88.2oE) lying near the Sikkim-Nepal border, about 68 km northwest of Gangtok, Sikkim with the depth of its hypocenter at about 10 km. As per the USGS estimates 2, the epicenter of this strong earthquake (6.9 Mw) lies slightly west of the location shown by IMD. This earthquake was widely felt in Sikkim, West Bengal to Rajasthan in the west and the northeastern states of India, and also in Nepal, Bhutan and Bangladesh. This major earthquake triggered several landslides in the region and a large number of which were studied during a recent post-earthquake fieldtrip (22-29 September 2011) to the Darjeeling-Sikkim Himalayas. The fieldwork was planned within four days’ of the event to the worst-affected areas in Sikkim-Darjeeling Himalayas that are accessible by roads. The aim of this study was to rapidly assess the damage caused by these earthquake induced landslides along with collection of the relevant landslide-related attributes for inventory and further study.
It is also pertinent to mention here that moderate to heavy monsoon rainfall prior to the occurrence of 18th September 2011 earthquake, during and post earthquake event is reported from some areas, which perhaps also contributed to some extent in lowering the shearing strengths of already-loosened (due to earthquake shaking) slope forming mass and ultimately triggered some landslides at selected locations just immediately after the earthquake shock. Due to this reason, it was considered wise to name these landslides as earthquake induced landslides instead of the co-seismic landslides in truest sense. Although, present field observation took due care not to mix up with landslides that are triggered by rainfall prior to 18th September earthquake.

Study area & Seismicity

The study area falls within the Lesser and Higher Himalayan regions with an elevation ranging from 65 m (around Dudhia, Darjeeling District) through 800-1200 m around Ranipul, Mangan, 1400 m around Darjeeling, 1800-2200 m around Gangtok, Pelling, Ravangla to 2800–3200 m around Kyangsla (near Nathula) with elevations increasing gradually from south to north. In the Lesser Himalayas towards south, the slope is gentler and in the undulating stretches, numerous streams and rivulets flow along the depression and finally join with the trunk streams. In the Higher Himalayan terrain, the topography is highly rugged, characterized by steep slopes with prominent gully erosion. The Tista-Rangit water divide is the main north-south water divide within the Sikkim Himalayas. Another north-south water divide is between Lachen Chu & Lachung Chu which starts at about 3000 m and slowly increases up to 6700 m. North of Dikchu, steep ridges on the eastern side are there but of smaller extent as the Tista valley is sub-divided by the water divide between Lachen Chu and Lachung Chu. On the western part long ridges are present – these are Talang Chu and Zemu Chu water divide. Geologically, the mountainous regions of the Darjeeling and Sikkim Himalayas are part of the active Himalayan Fold-Thrust Belt (FTB), which is geologically and structurally complex exposing a number of overturned (towards south) and thrusted sequence of variably metamorphosed pelitic and psammitic rocks over Mesozoic (Gondwanas) and foreland rocks composed of Tertiary (Siwaliks) sediments in the south³.
As per the Seismic Zonation Map of India⁴ the state of Sikkim comes under Seismic Zone IV – a zone of considerable vulnerability. The nearby region in the further north comes under Zone V and is highly susceptible to moderate to major earthquakes. In this area, most of the previous earthquakes were of shallow focus (< 40 km) and are commonly of 4.5 to 5.5 Magnitudes on the Richter scale. The regional distribution of earthquakes and lineaments/faults in Sikkim and adjoining Darjeeling areas indicates that a number of past moderate (M 5.0 to 5.9) and slight (M 3 to 5) earthquakes⁵ are clustered around the Tista Lineament trending NW-SE direction. Northern extension of the Tista lineament cuts across the NE-SW trending Kanchanjungha lineament. Another NW-SE trending lineament marked as a fault along the Tista River between Lachen and Chungthang (and further southeast) appears to have been the cause of some high Magnitude earthquakes in the region⁶.

Fig. 1: Map showing locations of 18 September 2011 Sikkim earthquake induced landslides observed along important road-corridors in Sikkim-Darjeeling Himalayas (in background multi-spectral IRS P-IV Satellite’s LISS III image of 2005 was used). The locations are plotted using Geographic Coordinates in Latitudes/Longitudes using WGS 84 global datum and UTM projection parameters.

Earthquake induced landslides

Due to the 18th September 2011 Sikkim earthquake (M: 6.8), several “new” and a few “reactivated” landslides have occurred right from the Himalayan foot-hill region (e.g., Dudhia in Kurseong Sub-division, Darjeeling District, West Bengal) up to the higher Himalayan range in the higher reaches of Sikkim-Darjeeling Himalayas. The new landslides that occurred in the lower elevations are mostly concentrated within the terrace deposits of trunk streams such as Tista, Rangit and Balason etc. and within the old colluvial deposits on the lower reaches of slope adjacent to trunk streams (e.g., Jorethang-Rishi-Legship section along the right bank of Rangit river). In the slopes having steep relief, the frequencies of rock/debris fall are more than to slides, whereas field observation clearly indicated that proximal to epicentral region, frequencies of both rock fall and rock slides are much higher than the debris/soil slides and the same are more concentrated towards the crest of steep ridges. Recent field observation of the landslide-related damages further indicated that lithology and geomorphology also played a significant role in causing these earthquake induced landslides. The debris-laden slope which is made of loose unconsolidated material and the slope covered by thin unconsolidated scree deposits have been more prone to failure by this earthquake. Frequency of rock fall and rockslides are more in areas which are generally vulnerable due to steep slope, weathered and fractured lithology and unfavourably jointed and kinematically-unstable slopes.

for more, go to: http://earthquake-report.com/2011/11/25/earthquake-induced-landslides-in-the-sikkim-darjeeling-himalayas/

Series of Earthquakes off New Zealand

Posted on November 18, 2011 by marcia

Series of strong to very strong earthquakes out of the New Zealand North Island coast

Last update: November 18, 2011 at 11:03 am by By Armand Vervaeck and James Daniell

Earthquake overview : 3 earthquakes have struck 100 km out of the New Zealand East Cape coast. The earthquakes were largely observed by people on the East Cape. The earthquake was felt as far as Rotorua.

“I have Felt it” Reports –> see below + Let us know “how you have felt this earthquake”
To read the full story as it happened, we advise our readers to start at the lower part of the page (earthquake data).

Isoseismal map – image courtesy Geonet GNS Science

Update : Historic powerful earthquakes in the same area :
Same distance from the coast : M 7.0 and M 6.6 in 1995
Close to the coast : M 6.7 in 1914 and M 6.3 in 1956

Update : According to the USGS, who has reported an epicenter closer to the coast, the following theoretical MMI numbers could be expected : 213 MMI V, 6,000 MMI IV, 288,000 MMI II and III. These numbers are contradicted by the Geonet reported numbers and the registered shaking values. The current experience, like so many other experiences in the past, are showing the importance of a tight seismograph network. Especially epicenter location and depth have often even bigger error margins than officially reported in their data sets.

Update : There was NEVER a tsunami risk

Update : The earthquake has been felt as far as Rotorua

Update : Reports from New Zealanders reveal a max. MMI IV (light shaking). Although the numbers are looking very strong, only 26 people have reported the earthquake to Geonet. Both other earthquakes were only felt by very few people. MMI IV in New Zealand gets the notion : largely observed

Update : The epicenter is on top of a subduction slope in front of the coast. The subduction slope are in fact 2 tectonic plates gliding below each other. The damaging Christchurch earthquake was triggered by the same tectonic movements.

Update : We do NOT expect the M 6.1 earthquake to be damaging because of the depth of the hypocenter and the distance out of the coast.

Update : We have initiated this article after the 3th quake, the 6.1 magnitude earthquake.

Update : New Zealand GNS Science reports magnitudes of 5.3, 5.8 and 6.1 at depths of 12, 33 and 40 km. GNS Science data for New Zealand will be more precise than any other seismological agency in the world because of the many instruments they have installed all over New Zealand.

for more information, and updates, go to: http://earthquake-report.com/2011/11/18/series-of-strong-to-very-strong-earthquakes-out-of-the-new-zealand-north-i

New Canary Island Forming

Posted on November 17, 2011 by marcia

Undersea volcano about to create new Canary Island

By Duncan Geere

14 November 11

Volcanologists studying an undersea volcano erupting near the island of El Hierro believe that it’s just 70 metres from the surface and may create new land.

Over the past week or so, the geological upheaval in the Canary Islands has caused jets of water to rise more than 20 metres into the air and locals claim to have even seen rocks thrown out of the sea. Measurements taken by researchers show that seething water is significantly warmer than the surrounding sea. The culprit is the Canarian hotspot — the islands are underlain by a deep magma plume that is believed to have first appeared 60 million years ago.

Since July 2011, more than 10,000 small earthquakes have shaken the island of El Hierro and since October they’ve grown significantly stronger, with some surpassing four on the Richter scale. At the start of November, residents in the southern part of the island had to leave their homes after tremors hit the area and supherous gases drifted through. The Canary Islands’ volcanology institute,Involcan, has reported a three-fold increase in carbon dioxide levels.

Since then, however, the quakes have shifted from the south of the island to the north. While the southern tremors occurred at a depth of more than 10km, the northern ones have moved upwards and Spain’s national geographic institute has warned that there could be minor eruptions in or near the El Golfo valley on the northern coast of the island.

For the moment, however, there is no immediate risk of major surface eruption, so locals are canvassing for names for the imminent new territory. Proposed names, according to Spiegel Online, include “The Discovery”, “Atlantis”, and “The Best”.

from: http://www.wired.co.uk/news/archive/2011-11/14/canary-islands-volcano

Turkey Aftershocks

Posted on October 26, 2011 by marcia

New powerful and dangerous aftershock creates panic in Van and Ercis, Eastern Turkey

Last update: October 25, 2011 at 5:16 pm by By Armand Vervaeck and James Daniell

Earthquake overview : On 17:55 on October 25,2011 , a powerful 5.7 magnitude earthquake struck the already severely damaged Van – Ercis area.

Shaking map of the M 5.7 Van Ercis aftershock – image courtesy USGS

Update : At least one building collapsed because of this new aftershock

Update : The Search and rescue operations have been suspended for a while because of the safety of the SAR personnel

Update : People in Van panicked seriously with this new jolt

Update : Due to the constant aftershocks, people are trying to avoid being at the inside of houses and buildings. They know very well that very powerful aftershocks are part of a major earthquake.

Update : 70,000 people will have experienced a strong MMI VI shaking

Update : Data from the other seismological agencies :
EMSC : 5.5 @ 10 km
GFZ : 5.5 @ 10 km
AFAD : 5.5 @ 18.28 km
The impact of this aftershock maybe a little weaker because all the other agencies are measuring a 5.5 magnitude.

Earthquake Predictions 10/26-11/11 fr/Dr. RJ Roberts

Posted on October 25, 2011 by marcia

Table 48a. Regional forecasts for New Moon Period

from October 26-November 9* 2011 (UTC)

REGIONS USA/Canadian regions listed first, by latitude, then other regions in alphabetical order	Forecast Magnitude Ranges & Dates (UTC)	Observed Maximum Magnitude in each region	Accuracy compared to mid range (%)	Observed Date (UTC) & Location
Alaska USA Southern Region within ≈600 km of a newcenter at Lat 59.6 and Lon -148.9, about 185 km S of Anchorage.	M3.3-M5.3 expected about Oct 28+/-3 days (posted 0425 hours 19th Oct)
Vancouver Is. and Seattle Regions CANADA/USA New zone within ≈525 km radius ofTofino, B.C. at Lat 49.159 and Lon -125.874	M2.6-M4.6 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
California –Oregon USABorder Region New zone Coast & Off Coast within ≈550 km of a center at Lat 41.29 Lon -125.95 160 km west of Orick, CA	M3.1-M5.1 expected about Oct 29+/-3 days (posted 0425 hours 19th Oct)
California 1. New zone‘Northern and Central CA’ (& Western Nevada) within ≈450 km radius ofRedwood Valley, CAat Lat 39.265 and Lon -123.204. Includes events off the coast near Eureka, CA, in the Triple Junction Region. **see table footnote	M2.7-M4.7 expected about Nov 3+/-3 days (posted 0425 hours 19th Oct)
California 2. Central, Southern, & Baja California Regions New zone Within ≈400 km of Beaumont, CA, at Lat 33.930 and Lon -116.978 **see table footnote	M2.8-M4.8 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
New Madrid Region Central USA New zone Within ≈550 km of a center at Springfield, Missouri, Lat 37.214 Lon -93.293 Extends to Central Oklahoma	M2.0-M4.0 expected about Nov 4+/-3 days (posted 0425 hours 19th Oct)
Hawaii USA Within 500 km of a center at Lat 19.62 Lon -155.5 on the Island of Hawaii	M2.4-M4.4 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Caribbean 1. Puerto Rico and Virgin Islands Region within ≈225 km of Fajardo, Puerto Rico, at Lat 18.326 & Lon -65.652,	M2.6-M4.6 expected about Oct 29+/-3 days (posted 0425 hours 19th Oct)
Caribbean 2. Haiti & Dominican Republic,SE Cuba & Jamaica Region within ≈600 km of Port-au-Prince, Haiti, at Lat 18.54 & Lon -72.334	M3.4-M5.4 expected about Nov 1st+/-3 days (posted 0425 hours 19th Oct)
Bucharest Romania Region New zone, Europe within ≈250 km of Bucharest at Lat 44.44 & Lon 26.093. Includes part of Northern Bulgaria.	M2.8-M4.8 expected about Nov 3+/-3 days (posted 0425 hours 19th Oct)
Chile 1. Northern Region within≈600 km of a center point 37 km NNE of ANTOFAGASTA, CHILE at Lat -23.34 Lon -70.29 (zone revised 3rd July 2011)	M3.8-M5.8 expected about Nov 5+/-3 days (posted 0425 hours 19th Oct)
Chile 2.Central Region within 500 km of Santa Cruz, Central Chile, at Lat -34.63 Lon -71.359	M4.1-M6.1 expected about Oct 29+/-3 days (posted 0425 hours 19th Oct)
China* Within 650 km of Liangshan, Sichuan at Lat 27.880 Lon 102.264 *Forecasts for China will be for the largest quake expected in the FULL lunar month (FM + NM periods). More exact timing cannot be forecast because of inadequate amounts of data readily available from China	No forecast
Colombia Region within 600 km of ARUSI, Colombia, Lat 5.583 Lon -77.484, on the coast Extends from Panama City region to Western Venezuela	M3.6-M5.6 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Fiji-Tonga Region within ≈500 km of a center point at Lat -20.67 Lon -178.4	M4.3-M6.3 expected about Nov 5+/-3 days (posted 0425 hours 19th Oct)
Greece New zone within 300 km of a center point at ITEA, Greece (Lat 38.435 & Lon 22.422)	M3.3-M5.3 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Guatemala Coastal Region within ≈300 km of a center point at Lat 14.07 Lon -91.92 offshore Guatemala, extending NW to southern Chiapas, Mex., & SE to El Salvador.	M3.3-M5.3 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
El Salvador -Costa Rica Region includes southeast Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica within ≈500 km of a center point at La Trinidad, Nicaragua (Lat 12.566 Lon -86.178) Zone revised 19th April.	M4.2-M6.2 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Indonesia 1.Sumatra Northern Region within ≈500 km of Medan, Northern Sumatra Lat 3.6 Lon 98.67	M4.3-M6.3 expected about Nov 5+/-3 days (posted 0425 hours 19th Oct)
Indonesia 2.Sumatra Southern Region within ≈350 km of Bengkulu Utara, Southern Sumatra, centered at Lat -2.67 and Lon 101.34 (revised region on 18th April, at 1205 hrs)	M4.3-M6.3 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Indonesia 3.Sunda StraitSouthern Sumatra to Java Region includes very southern Sumatra & Western Java, within ≈450 km from a center in Sunda Strait at Lat -5.869 Lon 105.762	M3.8-M5.8 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Italy Region within ≈500 km of a center in the Tyrrhenian Sea at Lat 40.28 Lon 11.88 (now excluding Alpine Northern Italy and Bosnia/ Montenegro Regions across the Adriatic Sea)	M3.1-M5.1 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Japan 1. Hokkaido Region & Northernmost Honshu Region within ≈500 km from Yubetsu, Hokkaido Lat 44.2 Lon 143.62 **see table footnote	M4.6-M6.6 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Japan 2. Honshu – Northern Region within ≈500 km of the M9.0 epicenter off East Coast of Honshu at Lat 38.322 Lon 142.369**see table footnote	M4.1-M6.1 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Japan 3.Honshu – Southern Region within ≈500 km of center ≈248 km SSE of Nagoya at Lat 33.144 Lon 138.040**see table footnote	M4.5-M6.5 expected about Nov 3+/-3 days (posted 0425 hours 19th Oct)
Kazakhstan, Kyrgyzstan, Tajikistan (and part of Southern Xinjiang, China) New zone within ≈550 km of a NEW CENTRE near the border of Southern Xinjiang and Tajikistan, 66 km W of Kashgar, Xinjiang, China at Lat 40.58 Lon 77.286	M4.7-M6.7 expected about Oct 29+/-3 days (posted 0425 hours 19th Oct)
Mexico Southern Region within ≈575 km of Tlaxiaco, Oaxaca, Mexico, at Lat 17.280 Lon -97.671	M4.0-M6.0 expected about Oct 31+/-3 days (posted 0425 hours 19th Oct)
New Britain Region, PNG within 400 km of a center at KImbe, NB, at Lat -5.548 Lon 150.140	M4.1-M6.1 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
New Zealand “Northern Region” within ≈400 km of Taupo, North Island, New Zealand Lat -38.687 Lon 176.07, including Nelson region and North tip of South Island **see table footnote	M3.9-M5.9 expected about Oct 30+/-3 days (posted 0425 hours 19th Oct)
New Zealand Southern Region within 500 km from Christchurch, South Island Lat -43.527, Lon 172.622 **see table footnote	M3.8-M5.8 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
New Zealand Lower South Island New zone within ≈450 km of Queenstown at Lat -45.030 and Lon 168.66 **see table footnote	M3.9-M5.9 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Pakistan Islamabad Regionwithin ≈425 km of Islamabad, Pakistan (Lat 33.71 Lon 73.07) (includes Hindu Kush, Afghanistan)	M3.8-M5.8 expected about Nov 3+/-3 days (posted 0425 hours 19th Oct)
Peru Region North to South within ≈1000 km of LIMA center, Lat -12.045 and Lon -77.028	M3.7-M5.7 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Philippines Region Philippines Region within ≈600 km of a center point at LABO, Lat 14.15 Lon 122.673	M4.0-M6.0 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Samoa/Tonga within ≈350 km of a center point at Lat -15.125 Lon -172.617	M4.3-M6.3 expected about Oct 31+/-3 days (posted 0425 hours 19th Oct)
Solomon Is’- Bougainville Region within ≈600 km of center at Lat -8.41 Lon 158.66	M4.5-M6.5 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Spain and Portugal – Southern Regions Plus Strait of Gibraltar and Northern Morocco within 450 km of a center NNE of Córdoba, Spain, at Lat 38.662 Lon -4.567	M2.6-M4.6 expected about Oct 30+/-3 days (posted 0425 hours 19th Oct)
Taiwan Region within 225 km of M7.7 center (1999) at Lat 23.77 and Lon 120.98	M3.5-M5.5 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Tibetan Plateau and Himalayan Region includes cities like Kathmandu, New Delhi, and Islamabad New zone within ≈900 km of a Tibetan center located at Lat 32.28 Lon 81.98	M3.8-M5.8 expected about Oct 29+/-3 days (posted 0425 hours 19th Oct)
Turkey within ≈425 km of a center at INSTANBUL, Turkey, at Lat 41.005 Lon 28.976 (region includes most of Western & Central Turkey, plus regions of Aegean and Black Seas)	M2.8-M4.8 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)
Vanuatu New zone within ≈350 km from a center at Lat -19.182 and Lon 168.270, 160 km S of PORT-VILA, Vanuatu	M4.7-M6.7 expected about Nov 6+/-3 days (posted 0425 hours 19th Oct)

Large Kermadec Islands Earthquake

Posted on October 21, 2011 by marcia

Second massive Kermadec Islands earthquake in 4 months time

Last update: October 21, 2011 at 11:10 pm by By Armand Vervaeck and James Daniell

being dangerous for populated islands. See links above

Information Bulletin Supplement Pacific Ocean :
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 ARE OBSERVED FOR TWO HOURS AFTER THE ESTIMATED TIME OF ARRIVAL 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 THE CONTINUING SEA LEVEL CHANGES AND RAPID CURRENTS. AS LOCAL CONDITIONS CAN CAUSE A WIDE VARIATION IN TSUNAMI WAVE ACTION THE ALL CLEAR DETERMINATION MUST BE MADE BY LOCAL AUTHORITIES. NO TSUNAMI THREAT EXISTS FOR OTHER COASTAL AREAS IN THE PACIFIC ALTHOUGH SOME OTHER AREAS MAY EXPERIENCE SMALL NON-DESTRUCTIVE SEA LEVEL CHANGES LASTING UP TO SEVERAL HOURS
NOAA Pacific Ocean message :
NO DESTRUCTIVE WIDESPREAD TSUNAMI THREAT EXISTS BASED ON HISTORICAL EARTHQUAKE AND TSUNAMI DATA.
NOAA Hawaii message :
BASED ON ALL AVAILABLE DATA A DESTRUCTIVE PACIFIC-WIDE TSUNAMI IS NOT EXPECTED AND THERE IS NO TSUNAMI THREAT TO HAWAII. REPEAT. A DESTRUCTIVE PACIFIC-WIDE TSUNAMI IS NOT EXPECTED AND THERE IS NO TSUNAMI THREAT TO HAWAII.

Local tsunami in an unpopulated area – courtesy GDACS

Update:The earthquake has been felt in the North Island of New Zealand, more than 1000 km away from the epicenter.

Raoul island is too far away to experience a destructive shaking. A tsunami was generated with limited wave heights and was not expected to be dangerous in New Zealand or Tonga.

Understanding this earthquake

The October 21, 2011 Kermadec Islands region earthquake occurred near the Kermadec Trench where the Pacific Plate begins its decent into the mantle beneath the eastern edge of the Australian Plate. At the latitude of this earthquake, the Pacific Plate is converging with Australia in a westward direction at a velocity of approximately 61 mm/yr. The preliminary mechanism and depth of the event suggest it ruptured a reverse fault within the oceanic lithosphere of the Pacific Plate; the initial location indicate a source slightly to the east of the trench, outboard (seaward) of the subduction zone itself, and thus not on the thrust interface between the Pacific and Australian plates.

The October 21 earthquake struck in an oceanic region with few nearby populations, approximately 500 km south of Tonga and 700 km north of New Zealand. This region of the Tonga-Kermadec subduction zone experiences reasonably high levels of seismic activity, with nearly 50 events of M 6.5 and above over the past 38 years, and 5 greater than M 7.5. Two of these, M 7.8 and M8.2 earthquakes on the same day in 1976, occurred just over 100 km west-northwest of todays event; an M7.8 event in 1978 struck nearly 250 km to the southwest, and an M 8.3 event occurred in October 1986, about 80 km to the north. None of these events have recorded damage or casualties.

In July of this year, a M 7.6 event occurred approximately 45 km to the south-southwest of the October 21 earthquake, breaking a normal fault within the subducting Pacific plate also very close to the Kermadec Trench. This event was notable because it triggered a large number of thrust-faulting aftershocks to the west of the plate boundary, on or close to the interface between the Pacific and Australian plates. The October 21 earthquake may be related to that aftershock sequence.

for more, go to: http://earthquake-report.com/2011/10/21/second-massive-kermadec-islands-earthquake-in-4-months-time/

Mauna Kea, Hawaii Earthquake Swarm

Posted on October 20, 2011 by marcia

Last update: October 20, 2011 at 1:56 pm by By Armand Vervaeck

October 20, 2011 By Armand Vervaeck

The dry summit environment of the summit of Mauna Kea – The white points on the summit are the astronomical telescopes – Image courtesy Tony Romaine

Description: At 00:10 AM UTC October 20, a moderate earthquake with a magnitude of 4.5 and a depth of 18.8 km attracted our attention. To our surprise the epicenter was located below the slopes of Mauna Kea, an active shield volcano who’s last eruption occurred at approx. 2,400 BC.

Update 13:37 UTC : The presentearthquake swarm is not necessarily to be linked to volcanic activity since occasional swarms have been registered since 25 years. The swarms are linked to structural adjustments within the Earth’s crust due to the heavy load of Mauna Kea.
A similar earthquake swarm occurred in March 2010. The aftershocks (just like they are occurring now) continued for many days in a row.

Update 12:28 UTC : Mauna Kea shield volcano is presently called “dormant”.

Update 11:13 UTC : USGS maintains her NORMAL green color alert (no problem)

Update 10:23 UTC : Since the mainshock at 00:10 earlier today, we noticed 38 other earthquakes. The shallowest of the +1 magnitude earthquakes was at a depth of 14.3 km.

The shallower earthquakes at Fern forest and Volcano have to be linked to the Kilauea complex.
21 km (13 miles) SE (137°) from Waimea, HI and 23 km (14 miles) SSW (199°) from Honokaa, HI

Earthquake swarm below Mauna Kea on October 20 2011

for more, go to: http://earthquake-report.com/2011/10/20/mauna-kea-hawaii-intriguing-earthquake-swarm-below-the-astronomical-observatories-volcano/

Strong Earthquake-Amur Region of Russia

Posted on October 14, 2011 by marcia

Very strong shallow dangerous earthquake in Amur area, Russia – many aftershocks are reported

Last update: October 14, 2011 at 2:03 pm by By Armand Vervaeck – James Daniell – Szombath Balazs

arthquake overview : A 5.9 magnitude strong earthquake hit Amurskaya Oblast, Russia. The hypocenter was located at 13.8 km depth. The epicenter was close to Skovordino a town with over 10,000 inhabitants.

Village and landscape in the earthquake area – image courtesy Tanya Konchik

UPDATE 10:54 UTC : We have found no evidence yet of serious damage and/or injuries

UPDATE: Authorities are talking about “awave of aftershocks“. People walking in the streets of Chita said that “The buildings were moving objects“.

UPDATE: The power supply was temporarily down because of the failure of 2 power substations at Bam. 4 hours 25 minutes later evrything was back to normal.

UPDATE: The earthquake has been calledAmur earthquake by local authorities.

UPDATE: According to experts, the epicenter of the earthquake was located 7 km east of the village Tahtamygda Skovorodinsky district, 134 km southwest of Tynda

UPDATE: * The power supply has been fixed, however as they expect new tremors, delays are expected.
* PAGER has updated the shaking damage estimate to be around $2-3 million (median estimate) .

UPDATE: The Russian Ministry for Emergency operations reports that : the earthquake occurred in the Amur region, some 20 km from Skovorodino, the end point of the current 600,000 barrels/day ESPO pipeline where crude is loaded into railroad tanks for further transportation to Kozmino. Workers who are inspecting the pipeline have not yet reported any damage yet.

Undersea Volcano Near Canary Islands-Eruption Effects

Posted on October 11, 2011 by marcia

El Hierro. Google Maps

Spain’s Instituto Geográfico Nacional (IGN) confirmed on Tuesday that an underwater eruption has occurred five kilomtres off the southern coastline of El Hierro, the smallest of the Canary Island. The eruption is Spain’s first since the eruption in 1971 of the Teneguía volcano on the island of La Palma (Canary Islands).

Scientists Monitor Underwater Volcano Eruption Near El Hierro

By MARK DUNPHY – Tue Oct 11, 2:53 p

The IGN says all three of its seismic stations on El Hierro in the Canary Islands have registered a volcanic tremor of low frequency in the south of the island at La Restinga (population 547), the southern-most village in the Canaries. Residents of the town were summonsed to a local football field on Tuesday afternoon to be briefed on provisional evacuation procedures in the event of another eruption closer to the shore.

Scientists from IGN and CSIC (Consejo Superior de Investigaciones Científicas), meanwhile, have conducted a reconnaissance flight over the sea to the area south of the island, where they have located dead fish floating on the surface five kilometres from the coast. The dead fish were identified in an area where lower seismic magnitude occurred on October 9, at a depth of approximately 2 km.

The present volcanic activity is understood to be occurring at a depth of 600 metres (just under one kilometre) below sea level, in the Las Calmas sea.

Scientists from IGN, CSIC and the University of Cadiz have established their monitoring base at La Restinga. Efforts are underway to determine if the subsea volcanic vent is widening and if so, in which direction (away or toward El Hierro).

Initial reports of the eruption were received from crews on board four separate ships. Local media agency Canarias7 reported on Monday that Government authorities have suspended ferry activities to and from the 285 square-kilometre island.

English language newspaper islandconnections.eu reported: “The martime chief for the province of Santa Cruz de Tenerife Antonio Padrón has issued a recomendation that boats should not sail closer than four miles off El Hierro. Divers have also been told to suspend all activities.

El Hierro (highlighted) on Google Earth

The eruption takes place amidst an unprecedented earthquake swarm in El Hierro. The number of earthquakes recorded since July 17, 2011 on El Hierro has now exceeded 10,000.

Hierro, a shield volcano, has had a single historic eruption from the Volcan de Lomo Negro vent in 1793. The eruption lasted approximately one month and produced lava flows.

The recent surge in the number and intensity of earthquakes prompted officials from the IGN and The Canary Islands Government to raise the alert level for the Hierro volcano to ‘Yellow’ late last month. The alert remained in place on Monday, but the estimated 11,000 residents of El Hierro were being reassured not to be alarmed.

The majority of the earthquake activity shifted from El Golfo in the island’s northwest to beneath the Las Calmas Sea in the south earlier this month. Surface deformations exceeding 35mm have also been recorded on the island in recent weeks.

Evacuations

A dramatic rise in recorded earthquakes on El Hierro prompted officials to evacuate some local residents, shut El Hierro’s main tunnel, and close local schools on 27 September.

The Spanish Civil Guard (Guardia Civil) advised almost 50 residents of the municipality of La Frontera to leave their homes because of landslide fears. Two units of the Spanish military’s emergency intervention unit (EMU) were also placed on standby to depart the nearby island of Tenerife to assist in the possible evacuation of hundreds of other El Hierro residents.

Meanwhile, the island’s main tunnel (Tunel del Golfo), which links Frontera to Valverde, was shut forcing motorists to travel across the 280-sq-km island via a mountain road. The Cabildo de El Hierro also ordered the closure of schools.

Canary Islands Volcano Yellow Alert

Posted on October 10, 2011 by marcia

El Hierro Volcano (Canary Islands) : October 10 : PEVOLCA latest report

Last update: October 10, 2011 at 9:49 pm by By Armand Vervaeck and James Daniell

Parador de El Hierro, gives a good idea on the coastline – Click on the picture to watch a video

Update 10/10 – 21:31 UTC : Fishing vessels have been ordered not to throw their nets in the expected eruption area. As far as now, no gases or bubbles have been detected in the area which is supposed to be the eruption area. This does not necessarily mean that there is no eruption, but that the depth of the magma vent is at least several hundred meters below sea level.
In the meantime, the harmonic tremors are unchanged (see link below).
Emergencia El Hierro has not published a new report tonight.

Update 10/10 – 17:01 UTC : Ramon Ortiz, a vulcanologist specialized in Canary Island volcanoes and currently advising the authorities, says in ElMundo that today’s eruption will be probably at a depth greater than 600 meter below sea level and about 5 km to the southeast of El Hierro.
Ortiz also said that the the Harmonic Tremors which started this morning showed that the eruption had started. They were reported in this site only hours after they started (see link and description below).
The latest eruption on the Canary Islands took place on La Palma Island in 1971 (see the video below from this eruption).

IMPORTANT UPDATE 14:31 UTC : PEVOLCA has just published a Press Statement that it is still unsure that an eruption is going on in the Las Calmas Sea. Scientists of IGN which make part of the PEVOLCA committee have stated that IGN has recorded the emission of volcanic gases at the south side of the island. The committee stresses that the gases are NOT dangerous for the population.
Additionally IGN reported that the emission might also be an eruptive phase but at the present time there is no 100% proof for it. A certainty however, IGN reported, is that “purely volcanic harmonic tremors” have started.

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