http://staadprov8itutorials.blogspot.in/
http://engineeringseismologywithmearul.blogspot.in/
http://archicad360degree.blogspot.in/
http://facade360degree.blogspot.in/
http://civilstructuralenggvbcodings.blogspot.in/
http://perfectwindows7.blogspot.in/
http://archicad360degree.blogspot.in/
http://facade360degree.blogspot.in/
http://civilstructuralenggvbcodings.blogspot.in/
http://perfectwindows7.blogspot.in/
Earthquake monitoring
India Meteorological Department (IMD) is the nodal agency of Government of India responsible for monitoring seismic activity in and around the country. IMD has rendered more than a century of seismological service to the nation with the first seismological observatory of the country having been set up by the department at Kolkata in 1898. The operational task of the department is to quickly estimate the earthquake source parameters immediately on occurrence of an earthquake and disseminate the information to all the user agencies including the concerned State and Central Government agencies responsible for carrying out relief and rehabilitation measures. The information relating to under-sea earthquakes capable of generating tsunamis on the Indian coastal regions is also disseminated to all concerned user agencies including the Indian National Centre for Ocean Information Services (INCOIS), Hyderabad for issue of tsunami related messages and warnings. The earthquake information is transmitted to various user agencies including public information channels, press, media etc. using different modes of communication, such as SMS, fax, email and also posted on IMD’s Website (www.imd.gov.in)..
National Seismological Network
India Meteorological Department is maintaining a country wide National Seismological Network (NSN), consisting of a total of 82 seismological stations, spread over the entire length and breadth of the country. This includes: a) 16-station V-SAT based digital seismic telemetry system around National Capital Territory (NCT) of Delhi, b) 20- station VSAT based real time seismic monitoring network in North East region of the country and (c) 17-station Real Time Seismic Monitoring Network (RTSMN) to monitor and report large magnitude under-sea earthquakes capable of generating tsunamis on the Indian coastal regions. The remaining stations are of standalone/ analog type. A Control Room is in operation, on a 24X7 basis, at IMD Headquarters (Seismology) in New Delhi, with state-of-the art facilities for data collection, processing and dissemination of information to the concerned user agencies
National seismological network of India (82)
S.N[Name of Station] Code [State] [Latitude/(Deg:Min)][Longitude(Deg:Min)][Height/above m. s.l.](Mtrs)
1 Ajmer AJM Rajasthan 26:28.75N 74:38.59E 540
2 Akola AKL Maharashtra 20:42.17N 77:00.92E 310
3 Allahabad ALBD Uttar Pradesh 25:18.54N 81:48.51E 107
4 Behraich BRCH Uttar Pradesh 27:34.00N 81:35.00E 123
5 Bhakra BHK Punjab 31:25.00N 76:25.00E 410
6 Bhavnagar BHV Gujarat 21:45.00N 72:08.60E 182
7 Bhopal BHPL Madhya Pradesh 23:14.46N 77:25.47E 520
8 Bhuj BHJ Gujarat 23:15.24N 69:39.24E 80
9 Bhubaneshwar BWNR Orissa 20:17.73N 85:48.35E 46
10 Bilaspur BLSP Chhattisgarh 22:07.75N 82:07.91E 398
11 Bokaro BOK Jharkhand 23:47.69N 85:53.15E 282
12 Kolkata CAL West Bengal 22:32.35N 88:19.84E 6
13 Chennai MDR Tamilnadu 13:04.08N 80:14.78E 15
14 Dehradun DDI Uttarakhand 30:19.35N 78: 3.33E 682
15 Delhi NDI NCT of Delhi 28:41.00N 77:13.00E 230
16 Goa GOA Goa 15:29.50N 73:49.48E 58
17 Jammu JMU Jammu & Kashmir 32:43.00N 74:54.00E 360
18 Jhansi JHNI Uttar Pradesh 25:27.95N 78:32.37E 250
19 Karad KAD Maharashtra 17:18.45N 74:11.00E 582
20 Kodaikanal KOD Tamilnadu 10:14.00N 77:28.00E 2345
21 Latur LATR Maharashtra 18:24.98N 76:33.57E 620
22 Lohaghat LGT Uttarakhand 29:25.00N 80:06.00E 1700
23 Mangalore MNGR Karnataka 12:56.50N 74:49.36E 31
25 Minicoy MNCY Lakshadweep Islands 8:16.89N 73:03.59E 2
25 Mumbai BOM Maharashtra 18:53.75N 72:48.76E 6
26 Nagpur NGP Maharashtra 21:06.11N 79:03.73E 311
27 Pithoragarh PTH Uttarakhand 29:35.00N 80:13.00E 1669
28 Portblair PBA A& N Islands 11:39.34N 92:44.64E 79
29 Pune POO Maharashtra 18:31.77N 73:50.95E 560
30 Sahibganj SHBJ Jharkhand 25:13.00N 87:40.00E 37
31 Salem SALM Tamilnadu 11:39.00N 78:12.00E 278
32 Shillong SHL Meghalaya 25:34.01N 91:51.36E 1600
33 Siliguri SLGI West Bengal 26:42.00N 88:25.00E 120
34 Srinagar SRIN Jammu & Kashmir 34:06.00N 74:51.00E 1587
35 Thein Dam THN Punjab 32:26.00N 75:43.00E 621
36 Thiruvananthapuram TRD Kerala 8:30.48N 76:57.51E 64
37 Valmikinagar VLK Bihar 27:19.00N 83:52.00E 100
38 Varanasi VAR Uttar Pradesh 25:18.00N 83:01.00E 88
39 Vijayawada VJWD Andhra Pradesh 16:31.00N 80:39.00E 18
40 Visakhapatnam VIS Andhra Pradesh 17:43.26N 83:19.72E 82
41 Lodi Road LDR Delhi 28:35.00N 77:13.00E 200
42 Campbell Bay CMBY A&N Islands 07:01.15N 93:55.59E 10
43 Dharmshala DHRM Himachal Pradesh 32:14.86N 76:18.40E 1995
44 Diglipur DGPR A&N Islands 13:10.67N 92:55.83E 30
45 Hyderabad HYB Andhra Pradesh 17:25.18N 78:33.11E 510
46 Shimla SMLA Himachal Pradesh 31:07.70N 77:10.00E 2200
47 Bahadurgarh BHGR Haryana 28:41.26N 76:56.33E 214
48 Sohna SONA Haryana 28:14.70N 77:03.78E 180
49 Bisrakh BIS Uttar Pradesh 28:34.26N 77:26.34E 200
50 Agra AGRA Uttar Pradesh 27:13.83N 77:56.63E 169
51 Kurukshetra KKR Haryana 29:57.69N 76:49.24E 2 5 0
52 Rohtak RTK Haryana 29:02.00N 76:24.86E 2 2 0
53 Kalagarh KALG Uttarakhand 29:30.37N 78:45.22E 1 8 1 4
54 Ausora ASR Uttar Pradesh 28:45.35N 77:46.33E 1 6 0
55 Rataul RTUL Uttar Pradesh 28:49.93N 77:20.51E 2 2 3
56 Kundal KUDL Haryana 28:08.65N 76:29.35E 2 2 7
57 Ayanagar AYAN NCT of Delhi 28:28.93N 77:07.60E 2 2 0
58 Onchagaon UGON Uttar Pradesh 28:18.60N 77:54.60E 237
59 Khetri KHE Rajasthan 28:04.44N 75:48.38E 3 2 0
60 Kalpa KALP Himachal Pradesh 31:32.77N 78.15.60E 2724
61 Jaisalmer JASL Rajasthan 26:55.46N 70:54.18E 223
62 Joshimath JOSM Uttarakhand 30:33.35N 79:33.49E 1889
63 Dhubri DHUB Assam 26:01.21N 89:59.73E 33
64 Mokokchung MOKO Nagaland 26:19.26N 94:30.94E 1353
65 Agartala AGT Tripura 23:53.33N 91:14.77E 18
66 Jorhat JORH Assam 26:44.58N 94:15.08E 79
70 Belonia BELO Tripura 23:14.91N 91:26.83E 20
67 Gangtok (Tadong) GTK Sikkim 27:19.15N 88:36.11E 1348
68 Kohima KOHI Nagaland 25:43.22N 94:06.48E 1353
69 Imphal IMP Manipur 24:49.8 N 93:56.79E 7 9 2
70 Aizwal AZL Mizoram 23:44.30N 92:41.38E 9 6 9
72 Silchar SILR Assam 24:46.88N 92:48.17E 1 8
73 Lekhapani LKP Assam 27:19.98N 95:50.76E 139
74 Ziro ZIRO Arunachal Pradesh 27:31.59N 93:50.99E 160
75 Tezpur TEZP Assam 26:37.01N 92:47.93E 83
76 Itanagar (Yupia) ITAN Arunachal Pradesh 27:08.68N 93:43.32E 214
77 Tura TURA Meghalaya 25:31.01N 90:13.45E 4 0 6
78 Guwahati GUWA Assam 26:11.60N 91:41.48E 8 8
79 Dibrugarh DIBR Assam 27:28.06N 94:54.67E 9 0
80 Tawang TAWA Arunachal Pradesh 27:35.64N 91:52.02E 2 9 7
81 Pasighat PASG Arunachal Pradesh 28:03.66N 95.19.56E 1 6 7
82 Saiha SAIH Mizoram 22:30.00N 93:00.00E 729
Seismic Zoning of India
Bureau of Indian Standards [IS-1893 – part – 1: 2002], based on various scientific inputs from a number of agencies including earthquake data supplied by IMD, has grouped the country into four seismic zones viz., Zone-II, -III, -IV and -V. Of these, zone V is rated as the most seismically prone region, while zone II is the least. The Modified Mercalli (MM) intensity, which measures the impact of the earthquakes on the surface of the earth, broadly associated with various zones, is as follows:
| Seismic Zone | Intensity on MMI scale | % of total area |
| II (Low intensity zone) | VI (or less) | 43% |
| III (Moderate intensity zone) | VII | 27% |
| IV (Severe intensity zone) | VIII | 18% |
| V (Very severe intensity zone) | IX (and above) | 12% |
Seismicity map of Indian region
with events of magnitude 5.0 & above (Up to June 2011)
SIGNIFICANT EARTHQUAKES IN AND AROUND INDIA
Date Epicentre Region Mag. Lat (0N) Long (0E)
1 1819 Jun 16 24.0 70.0 KUTCH, GUJARAT 8.0
2 1869 Jan 10 24.5 92.5 NEAR CACHAR, ASSAM 7.5
3 1885 May 30 34.1 74.8 SOPORE, JAMMU & KASHMIR 7.0
4 1897 Jun 12 25.9 91.0 SHILLONG PLATEAU 8.7
5 1905 Apr 4 32.3 76.3 KANGRA, HIMACHAL PRADESH 8.0
6 1918 Jul 8 24.5 91.0 SRIMANGAL, ASSAM 7.6
7 1930 Jul 3 25.8 90.2 DHUBRI, ASSAM 7.1
8 1934 Jan 15 26.6 86.8 BIHAR-NEPAL BORDER 8.3
9 1941Jun 26 12.4 92.5 ANDAMAN ISLANDS 8.1
10 1943 Oct 23 26.8 94.0 ASSAM 7.2
11 1950 Aug 15 28.5 96.7 ARUNACHAL PRADESH-CHINA BORDER 8.5
12 1956 Jul 21 23.3 70.2 ANJAR, GUJARAT 7.0
13 1967 Dec 11 17.4 73.7 KOYNA, MAHARASHTRA 6.5
14 1975 Jan 19 32.4 78.5 KINNAUR, HIMACHAL PRADESH 6.2
15 1988 Aug 6 25.1 95.1 MANIPUR-MYANMAR BORDER 6.6
16 1988 Aug 21 26.7 86.6 BIHAR-NEPAL BORDER 6.4
17 1991 Oct 20 30.7 78.9 UTTARKASHI, UTTRAKHAND 6.6
18 1993 Sep 30 18.1 76.6 LATUR-OSMANABAD, MAHRASHTRA 6.3
19 1997 May 22 23.1 80.1 JABALPUR, M.P. 6.0
20 1999 Mar 29 30.4 79.4 CHAMOLI, UTTARAKHAND 6.8
21 2001 Jan 26 23.4 70.3 BHUJ, GUJARAT 7.7
22 2004 Dec 26 3.3 96.1 OFF WEST COAST OF SUMATRA 9.3
23 2005 Oct 8 34.5 73.1 MUZAFFARABAD 7.6
24 2011 Sep 18 27.8 88.1 SIKKIM-NEPAL BORDER 6.9
Earthquake Measurement Scales
Earthquakes can be described by use of two distinctly different scales of measurement demonstrating
magnitude and intensity. Earthquake magnitude or amount of energy released is determined by use of a
seismograph, and instrument that continuously records ground vibrations. A scale developed by a seismologist named Charles Richter mathematically adjusts the readings for the distance of the instrument from the epicenter. The Richter scale is logarithmic. An increase of one magnitude signifies a 10-fold increase in ground motion or roughly an increase of 30 times the energy (see Table 2). Thus, an earthquake with a magnitude of 7.5 releases 30 times more energy than one with a 6.5 magnitude, and approximately 900 times that of a 5.5 magnitude earthquake. A quake of magnitude 3 is the smallest normally felt by humans. The largest earthquakes that have been recorded under this system are 9.25 (Alaska, 1969) and 9.5 (Chile, 1960).
Locating the Epicenter and Determining the Magnitudeof an EarthquakeMeasuring the S-P time interval
There are hundreds of seismic data recording stations
throughout the rest of the world. In
order to locate the epicenter of an earthquake, you need to
estimate the time interval between the arrival of the P and S
waves (the S-P interval) on the seismograms from at least
three different stations.You have to measure the interval to
the closest second and then use a graph to convert the S-P
interval to the epicentral distance. On the sample
seismogram at the right the vertical lines are spaced at 2
second intervals. The S-P time interval is about 36 seconds.
Determining the Earthquake Distance
You can now determine the distance from each seismic recording
station to the earthquake's epicenter using the known times of
travel of the S and P waves.
Examine the graph of seismic wave travel times (middle graph on
this page). There are three curves on the graph: The upper curve
shows S wave travel-time graphed versus distance, the center one
shows P wave travel time versus distance, and the lower one shows
the variation in distance with the difference of the S and P travel
times. It takes an S wave approximately 70 seconds to travel 300
kilometers.
How long does it take the P wave to travel this same distance?
For the rest of this exercise you won't be needing the individual S
and P curves, only the S-P curve. Using the example from above,
the 36 second S-P interval corresponds to a distance of about 355
km.
To determine the epicentral distance, we need a graph with
greater resolution and detail. The bottom graph shows an
expanded part of the S-P curve. Use the bottom graph for the
exercises
Finding the Epicenter on a Map
Once you have the epicentral distances, you can draw circles to
represent each distance on a map. The radius of each circle
corresponds to the epicentral distance for each seismic recording
station. Once you have drawn all three circles and located the
point where all three intersect, you will have successfully located
(triangulated) the epicenter of the earthquake.
Using this method to determine an earthquake's epicenter may
not result in an exact point for some earthquakes. Discounting
measurement errors, there are a number of factors that affect the
speed of earthquake waves. Among other factors, variations in
rock types through which the waves travel will change the actual
travel times and hence the S-P intervals.
.png)
Determining the Richter Magnitude
So far you have worked on locating the epicenter of an earthquake. The next questions to ask are "How strong was this particular earthquake and how does it compare to other earthquakes?"
There are many ways that one could evaluate the relative strength of an earthquake: from the cost of repairs resulting from damage, from the length of rupture of the earthquake fault, from the amount of ground shaking, etc. But determining the strength of an earthquake using these kinds of "estimators" is full of potential problems and subjectivity. For example, the cost of repairs resulting from a strong earthquake in a remote region would be much less than that of a moderate earthquake in a populated area. Furthermore, the degree of damage would depend greatly on the quality of construction. Also, only a few earthquakes produce actual ground ruptures at the surface.
A well-known scale used to compare the strengths of earthquakes involves using the records (the seismograms) of an earthquake's shock waves. The scale, known as the Richter Magnitude Scale, was introduced into the science of seismology in 1935 by Dr. C. F. Richter of the California Institute of Technology in Pasadena. The magnitude of an earthquake is an estimate of the
total amount of energy released during fault rupture. The Richter magnitude of an earthquake is a
number: about 3 for earthquakes that are strong enough for people to feel and about 8 for the Earth's strongest earthquakes. Although the Richter scale has no upper nor lower limits, earthquakes greater than 9 in Richter magnitude are unlikely. The most sensitive seismographs can record nearby earthquakes with magnitude of about -2 which is the equivalent of stamping your foot on the floor.
The Richter magnitude determination is based on measurements made on seisograms. Two measurements are needed: the S-P time interval and the Maximum Amplitude of the Seismic waves. The illustration at the top right on this page shows how to make the measurement of the S wave's maximum amplitude. The blue horizontal grid lines are spaced at 10 millimeter intervals. In this example the maximum amplitude is about 185 mm.
The Richter Nomogram
In the diagram to the right, the horizontal dotted line (A) represents the "standard" Richter earthquake. This standard earthquake is 100 km away and produces 1 mm of amplitude on the seismogram. It is assigned a magnitude of 3. Other earthquakes can then be referenced to this standard
Note that a 100 km-away earthquake of magnitude 4 would produce 10 mm of amplitude (line B) and a magnitude 5 would produce 100 mm of amplitude (line C) at the same distance. 1, 10 and 100 are all powers of 10 and this is why the Richter Scale is said to be "exponential." A change of one unit in magnitude (say from 4 to 5) increases the maximum amplitude by a factor of 10. The last line drawn, line D, shows the result for an earthquake that produces an amplitude of 150 at a distance of 600 km. Although only one amplitude measurement is necessary to estimate the magnitude of an earthquake, it is better to use measurements from several seismograph stations. This enables you to determine the magnitude value as an average of several values, thus increasing the likelihood that you are accurate in your estimate.
http://staadprov8i360degree.blogspot.in/
http://engineeringseismologywithmearul.blogspot.in/
about me.....arul.s+918438216968
contactmearul@gmail.com,arul.s@mfacade.comchennaitamilnaduindia
No comments:
Post a Comment