Predicted travel times of P wave of Magnitude 6.8 Earthquake of SIKKIM, INDIA 2011 September 18

The map below shows the predicted travel times of the compressional (P) wave from the earthquake location to points around the world. Spherically-symmetric IASP91 reference earth velocity model are used to compute travel time. The travel time computed in minutes. The heavy black lines shown are the approximate distances to the P-wave shadow zone (103 to 140 degrees). The table below depicts  theoretical P-Wave Travel Times in tabular form.

Predicted travel times of P wave of Magnitude 6.8 Earthquake of SIKKIM, INDIA 2011 September 18

 Theoretical P-Wave Travel Times:

City	Distance (degrees)	Travel Time (min:secs)	Arrival Time UTC	Phase
Kathmandu, Nepal	2.45	0:38.8	12:41:26.8	Pn
Beijing, China	26.39	5:34.9	12:46:22.9	P
Tokyo, Japan	44.25	8:07.8	12:48:55.8	P
Moscow, Russia	45.46	8:17.4	12:49:05.4	P
Agana, Guam	54.48	9:26.0	12:50:14.0	P
Nairobi, Kenya	57.01	9:44.1	12:50:32.1	P
Rome, Italy	61.79	10:17.2	12:51:05.2	P
Bergen, Norway	62.79	10:23.9	12:51:11.9	P
London, England	67.78	10:56.2	12:51:44.2	P
Anchorage, Alaska	79.78	12:06.6	12:52:54.6	P
Brisbane, Australia	83.04	12:23.9	12:53:11.9	P
Honolulu, Hawaii	99.79	13:42.4	12:54:30.4	Pdiff
Seattle, Washington	100.01	13:43.3	12:54:31.3	Pdiff
Bangor, Maine	104.80	14:04.6	12:54:52.6	Pdiff
Wellington, New Zealand	105.41	14:07.3	12:54:55.3	Pdiff
Ottawa, Canada	105.73	14:08.7	12:54:56.8	Pdiff
Duluth, Minnesota	105.88	14:09.4	12:54:57.4	Pdiff
Boston, Massachusetts	107.69	14:17.4	12:55:05.4	Pdiff
San Francisco, California	108.85	14:22.6	12:55:10.6	Pdiff
New York, New York	109.91	14:27.3	12:55:15.3	Pdiff
Philadelphia, Pennsylvania	110.89	14:31.6	12:55:19.6	Pdiff
Golden, Colorado	111.75	14:35.4	12:55:23.4	Pdiff
Washington, D.C.	112.29	14:37.8	12:55:25.8	Pdiff
Los Angeles, California	113.69	14:44.1	12:55:32.1	Pdiff
St. Louis, Missouri	113.94	14:45.2	12:55:33.2	Pdiff
Wichita, Kansas	114.66	14:48.4	12:55:36.4	Pdiff
Albuquerque, New Mexico	116.01	14:54.4	12:55:42.4	Pdiff
Phoenix, Arizona	116.23	14:55.3	12:55:43.3	Pdiff
Knoxville, Tennessee	116.35	14:55.9	12:55:43.9	Pdiff
Miami, Florida	125.63	15:37.1	12:56:25.1	Pdiff
Brownsville, Texas	126.42	15:40.6	12:56:28.6	Pdiff
San Juan, Puerto Rico	127.72	15:46.3	12:56:34.3	Pdiff
Mexico City, Mexico	132.62	16:08.1	12:56:56.1	Pdiff
Palmer Station, Antarctica	136.57	16:25.6	12:57:13.6	Pdiff
Lima, Peru	159.13	19:57.7	13:00:45.7	PKPdf

Intensities of M 6.8 Earthquake of SIKKIM, INDIA 2011 September 18

vulnerability of Structures

Overall, the population in this region resides in structures that are highly vulnerable to earthquake shaking, though some resistant structures exist. The predominant vulnerable building types are unreinforced brick masonry and rubble/field stone masonry construction.

Intensities of the Significant Cities on Modified Mercalli Intensity Scale (MMI)

MMI	City	Population
VI	Mangan	1k*
VI	Singtam	6k
VI	Namchi	1k
VI	Gangtok	31k
VI	Naya Bazar	1k
V	Rangpo	4k
V	Shiliguri	516k
IV	Thimphu	99k
III	Kathmandu	1,442k
III	Bhagalpur	362k
III	Patna	1,600k

* K= X 1000

Seismic details are:

2011 September 18 12:40:48 UTC : SIKKIM, INDIA 

Magnitude: 6.8

Date-Time : Sunday, September 18, 2011 at 12:40:48 UTC

Sunday, September 18, 2011 at 06:10:48PM at epicenter
Location : 27.730°N, 88.082°E

Depth : 20.7 km (12.9 miles)

Region : SIKKIM, INDIA

Distances: 69 km (43 miles) NW (310°) from Gangtok, Sikkim, India

120 km (74 miles) NNW (343°) from Shiliguri, West Bengal, India

 272 km (169 miles) E of KATHMANDU, Nepal

572 km (355 miles) N of Kolkata (Calcutta), West Bengal, India

Subduction Zones-Purple, Ridges-Red and Transform Faults Green

Location Uncertainty :  horizontal +/- 14.4 km (8.9 miles); depth +/- 7.4 km (4.6 miles)

Parameters : NST=258, Nph=258, Dmin=369.6 km, Rmss=1.17 sec, Gp= 29°, M-type=regional moment magnitude (Mw), Version=9

Magnitude 6.9 Earthquake of SIKKIM, INDIA 2011 September 18

2011 September 18 12:40:48 UTC : SIKKIM, INDIA 

Magnitude: 6.8

Date-Time : Sunday, September 18, 2011 at 12:40:48 UTC

Sunday, September 18, 2011 at 06:10:48PM at epicenter
Location : 27.730°N, 88.082°E

Depth : 20.7 km (12.9 miles)

Region : SIKKIM, INDIA

Distances: 69 km (43 miles) NW (310°) from Gangtok, Sikkim, India

120 km (74 miles) NNW (343°) from Shiliguri, West Bengal, India

 272 km (169 miles) E of KATHMANDU, Nepal

572 km (355 miles) N of Kolkata (Calcutta), West Bengal, India

Subduction Zones-Purple, Ridges-Red and Transform Faults Green

Location Uncertainty :  horizontal +/- 14.4 km (8.9 miles); depth +/- 7.4 km (4.6 miles)

Parameters : NST=258, Nph=258, Dmin=369.6 km, Rmss=1.17 sec, Gp= 29°, M-type=regional moment magnitude (Mw), Version=9

Mineral Structure of Black Cotton Soil of India

Black cotton soils occurs mostly in the central and western parts and covers approximately 20% of the total area of India. Highway and construction of structures on Black cotton soils has been a challenge to the respective engineers and designers because of its high swelling and shrinkage characteristics. This major group of soil consists of inorganic clays of medium to high compressibility. The Black cotton soils is very hard when dry, but loses its strength completely when in wet condition.

Black cotton soils of this particular region have liquid limit values ranging from 50 to 100%, plasticity index ranging from 20 to 65% and shrinkage  limit  from 9 to 14%. The amount of swell generally increases with increase in the plasticity index. The swelling potential depends on the type of clay mineral, crystal lattice structure, cation exchange capacity, ability of water absorption, density and water content.`

Swell in the vertical direction is called heave. Among the illite, kaolinite and montmorillinite clay minerals, the montmorillinite possesses the greatest ability to swell by illite. The Kaolinite does not swell. Black cotton soils are very hard in dry state and possess high bearing capacity. In summer, it is very common to see shrinkage cracks with hexagonal columnar structure, with vertical cracks as wide as 10mm extending up to a depth of 3m or more. Soils containing expansive clays become very sticky when wet and usually are characterized by surface cracks or a “popcorn” texture when dry. Therefore, the presence of surface cracks is usually an indication of an expansive soil.