Darb_e_Astaneh (Silakhor) Earthquake Report: March 31, 2006; ML=6.1

At 4:47 a.m. on March 31, 2006 an earthquake occurred in the South of Borujerd with several foreshocks, especially on March 30, 2006 with ML=4.6 and at 23:06 on March 30, 2006 with ML=5.1, and also with the aftershock at 5:01 a.m. on March 31, 2006 with ML=4.9 (Figure 1). According to the latest news reports, 66 fatalities, about 1280 injuries, and damage to 330 villages in the  Darb_e_Astaneh (Silakhor) region (surrounding Borujerd and Dorud) have been reported. The occurrence of this earthquake near the main Zagros fault (section of Dorud fault) shows the probability of further activity from this fault (Figure 2). IIEES's report on the previous earthquakes on May 3, 2005 shows that in this same region, a number of earthquakes of which the greatest magnitude was 4.9 occurred on May 3, 2005 – and caused one fatality and great panic among people of this region. The epicenter of the earthquake on March 31, 2006, was in the southeastern epicentral region of the May 3, 2005 earthquake and with a greater magnitude indicates the continuous activity of the current fault plain in the earthquake stricken region.
The occurrence of eight earthquakes between May 3-5, 2005 in the Borujerd region, 17 consecutive earthquakes with a magnitude of 2.5-4 between 21- 27 of November, 2004 in the Poldokhtar region and other similar cases all indicate the high seismic activity of this area of the earth's crust.
With regard to the increase in seismic activity of the region, IIEES has dispatched a specialized team to the region on March 31, 2006 with the aim of preliminary identification of the earthquake stricken region and installing a temporary seismic network with 6 seismic stations in the region. Until now, more than 60 aftershocks have been recorded by the broad band seismic network of IIEES in the region (Figure 2).
 

Figure (1): Records of the 31.3.2006  Darb_e_Astaneh (Silakhor), Lorestan earthquake and aftershocks at the IIEES broadband stations (INSN).

 

Active faults

In general the main trend of the active fault in the Zagros is in NW-SE and the main active faults in the Lorestan Province are shown in the Figure 3.

Figure (2): Map of the earthquake's epicenter on 31.3.2006  Darb_e_Astaneh (Silakhor) ML=6.1 and foreshocks and aftershocks of the earthquake (green circles are foreshocks and red circles are aftershocks).

 

Seismicity

The Zagros region is one the most active region in Iran (Figure 3). Table 1 shows the main instrumental seismic events in the Lorastan province.

Figure (3): Map of main faults and previous seismic events in Lorestan Province.

 

Table 1: Main seismic events in Lorestan Province (source IIEES website www.iiees.ac.ir)

Date

Time(UTC)

Lat.

Lon.

Depth

mb

MS

ML

Reference

1/23/1909

2:48:00

33

50

 

7.4

 

 

BS

3/21/1922

16:56:12

33

50

 

5.5

 

 

ISS

11/15/1927

17:39:12

33.5

48

 

4.7

 

 

ISS

7/15/1929

7:44:07

33.7

49.4

 

6.5

 

 

ISS

10/27/1929

16:42:57

33.5

48

 

5

 

 

ISS

1/22/1932

0:48:56

33.5

48

 

5

 

 

ISS

2/24/1936

16:29:31

33.5

48

 

5

 

 

ISS

11/4/1939

10:48:20

33.5

48.5

 

6

 

 

BOM

8/28/1941

0:18:35

33.4

47.3

 

4.7

 

 

ISS

3/12/1945

1:38:56

33.4

47.3

 

4.7

 

 

ISS

12/4/1955

14:02:05

33.5

48.7

 

5.2

 

 

ISS

8/14/1958

11:58:39

34.15

47.74

 

5.7

 

 

ISS

9/3/1958

1:34:06

34

47

 

5

 

 

USCGS

3/2/1959

11:54:17

33.12

49.46

 

5.2

 

 

ISS

4/2/1960

23:33:08

34.2

48.19

 

4.5

 

 

ISS

6/2/1960

12:42:38

33.05

48.78

 

5.2

 

 

ISS

10/3/1961

9:34:52

34.3

47.9

59

4.8

 

 

USCGS

10/28/1961

10:46:43

33.33

48.74

59

5

 

 

ISS

11/9/1962

1:44:25

33.53

47.16

56

5.2

 

 

ISS

6/30/1963

7:41:07

33.2

49.2

38

5.1

 

 

USCGS

11/26/1964

4:49:01

32.94

49.09

99

4.5

 

 

ISC

9/8/1965

5:35:44

32.9

48.4

50

4.7

 

 

USCGS

12/18/1967

22:49:28

33.46

46.95

49

4.6

 

 

ISC

5/22/1968

18:36:07

33.16

49.25

51

4.6

 

 

ISC

10/31/1969

8:53:26

33.2

47.9

51

5

 

 

USCGS

6/7/1970

17:48:33

33

49.4

50

4.7

 

 

USCGS

1/6/1973

20:01:51

33.1

48.33

70

4.6

 

 

ISC

11/5/1973

5:36:06

32.96

49.53

54

4.5

 

 

ISC

1/7/1974

15:24:38

33.3

47.9

32

5

 

 

USERL

1/7/1974

15:29:33

33.3

47.9

36

4.8

 

 

USERL

11/27/1974

7:39:15

33.2

46.9

31

4.9

 

 

USERL

12/27/1974

23:03:28

33.2

46.97

49

4.7

 

 

ISC

9/1/1975

23:15:52

33.32

49.1

16

4.9

 

 

USERL

11/7/1976

11:39:37

33.23

47.96

51

5.5

 

 

USERL

11/15/1976

8:36:43

33.25

47.93

49

5.4

 

 

USERL

1/4/1977

16:09:58

33.094

47.923

45

5.1

 

 

USCGS

1/18/1977

8:48:54

33.157

47.997

48

5.2

 

 

USCGS

5/11/1977

23:46:16

33.225

48.001

33

4.8

 

 

USCGS

3/3/1978

2:42:47

32.916

49.584

33

4.8

 

 

USCGS

6/22/1978

19:06:02

33.022

48.047

33

4.7

4.2

 

USCGS

7/24/1978

15:59:51

33.083

48.732

55

4.7

3.6

 

USCGS

3/31/1980

9:50:10

33.497

48.314

33

4.6

 

 

USCGS

11/17/1981

10:45:44

33.202

47.708

33

4.5

 

 

USCGS

12/24/1981

22:00:51

33.143

49.735

33

4.7

4

 

USCGS

9/1/1982

7:52:27

33.668

48.9

33

4.9

3.5

 

USCGS

3/12/1985

19:06:37

33.366

49.463

33

4.5

 

 

USCGS

11/23/1985

19:31:58

33.508

48.789

44

4.8

 

 

USCGS

9/9/1987

23:29:30

33.71

47.125

68

4.7

 

 

USCGS

2/19/1988

4:52:23

33.658

46.901

88

4.6

 

 

USCGS

10/10/1989

14:57:42

33.458

48.681

33

4.5

 

 

USCGS

1/16/1990

14:18:09

33.218

46.776

12

4.7

 

 

USCGS

5/24/1990

15:12:17

32.944

46.801

59

4.9

 

 

USCGS

8/4/1990

3:48:35

32.97

47.793

71

4.5

 

 

USCGS

6/19/1991

23:17:12

33.703

47.037

10

4.6

 

 

USCGS

7/7/1991

17:26:15

33.427

48.314

64

4.5

 

 

USCGS

12/14/1991

14:30:43

33.231

47.607

23

4.9

 

 

USCGS

3/7/1994

10:54:57

33.146

48.033

26

4.8

4.2

 

USGS

3/25/1995

11:56:47

33.83

47.9

33

4.6

 

 

USGS

4/10/1997

4:43:02

33.28

47.71

33

4.6

 

 

USGS

5/26/1997

1:49:34

32.94

47.03

33

4.7

 

 

USGS

6/2/1997

3:54:42

33.96

48.29

27

4.7

 

 

USGS

11/18/1997

6:56:57

33.05

48.08

33

4.6

 

 

USGS

10/4/1998

0:42:51

33.22

47.15

33

5.3

4.9

 

USGS

10/5/1998

2:52:13

33.34

47.33

33

5.2

4.9

 

USGS

8/1/1999

19:22:52

33.85

48.39

33

4.6

 

 

USGS

12/25/1999

3:39:29

33.33

47.1

33

4.7

 

 

USGS

8/5/2001

11:58:45

33

47.57

33

4.5

 

 

NEIC

2/19/2002

15:41:06

33.24

47.26

33

4.6

 

 

NEIC

10/25/2002

21:48:05

33.04

48.9

33

4.6

 

 

NEIC

11/21/2004

21:37:22

33.26

47.93

18

 

 

4.6

IIEES

11/21/2004

21:45:34

33.38

47.85

13

 

 

4.8

IIEES

11/22/2004

4:34:47

33.36

47.99

14

 

 

4.8

IIEES

5/3/2005

7:54:32

33.88

48.85

14

 

 

4.9

IIEES

 

Preliminary Action taken by IIEES:

IIEES has sent a team of multi-disciplinary experts to the region on 31.03.2006 to area and the result of observation will be posted soon at the www.iiees.ac.ir web-site.

According to the report the loss of life and property has been heavy. There is preliminary assessment of the event in FARSI at the www.iiees.ac.ir .

Pictures

 

 

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