|
A swarm of light to
moderate (M4.0-4.9 termed as "light" and M5.0-5.9 termed as
"moderate") earthquakes
began in the Andaman Sea along the Andaman Sea Ridge on 26 July
2009.
The blue
squares mark all earthquakes in this sequence that are also listed
in the table below. The latest event listed in the table is shown
as a red square.
The largest event recorded so far has been a Mb=5.3 earthquake at
05:14 UTC on 28 July 2009 (10:44 IST). Since the first event in
this sequence
at 06:45 UTC on 26
July 2009,
that was large enough
to be detected by global seismological networks, there have been
over thirty recorded events (4.4<M<5.3). At least six events have
had magnitudes greater than Mb=5.0 (5.0<M<5.3). Activity
appears to have reduced from thirty-two recorded events on 26 July
from 06:45 UTC to 23:59 UTC, to just four events on 27 July. The
last event large enough to be located globally occurred at 19:14
UTC on 28 July.
Thus far, none of the earthquakes are thought to have been felt in
the Andaman & Nicobar Islands or in coastal Thailand. However, if you felt any of
these earthquakes, please take the time
to fill out a
felt report questionnaire.
Due to the magnitudes of the earthquakes so far, the risk of a
local tsunami in the Andaman Sea from this sequence at this point
in time is minimal.
However, please be sure to
check for any near-real time changes in the
situation in the Indian Ocean at the Pacific Tsunami Warning
Centre (PTWC).
Earthquake swarms are common along the
Andaman Spreading Ridge and are associated with extension (sea
floor spreading also known as rifting) along this feature that
defines the boundary between the Burma and the Sunda micro-plates. This is the most significant swarm in the
Andaman Sea, in terms of the size of the events, since a swarm
between 26-30 January 2005 to the east of the islands of Nancowry
and Camorta in the Nicobar Islands.
|
Date |
UTC |
M |
T |
Latitude |
Longitude |
Depth |
Location |
Network |
|
28july09 |
19:14:05 |
4.9 |
Mb |
10.549 |
94.206 |
004.0 |
Andaman Sea Ridge |
NEIC |
|
28july09 |
05:14:58 |
5.3 |
Mb |
10.757 |
94.089 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
28july09 |
05:10:59 |
4.8 |
Mb |
10.460 |
94.500 |
010.0 |
Andaman Sea Ridge |
GSR |
|
27july09 |
21:15:01 |
4.8 |
Mb |
10.648 |
94.337 |
002.0 |
Andaman Sea Ridge |
NEIC |
|
27july09 |
12:08:15 |
4.8 |
Mb |
10.722 |
94.340 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
27july09 |
03:31:53 |
4.6 |
Mb |
10.710 |
94.200 |
033.0 |
Andaman Sea Ridge |
GSR |
|
27july09 |
02:09:16 |
4.8 |
Mb |
10.730 |
94.140 |
033.0 |
Andaman Sea Ridge |
GSR |
|
26july09 |
21:49.24 |
5.1 |
Mb |
10.599 |
94.217 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
19:45:06 |
5.0 |
Mb |
10.625 |
94.257 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
17:47:58 |
4.6 |
Mb |
10.620 |
94.300 |
026.0 |
Andaman Sea Ridge |
GFZ |
|
26july09 |
17:01:07 |
4.8 |
Mb |
10.780 |
94.480 |
033.0 |
Andaman Sea Ridge |
GSR |
|
26july09 |
16:53:11 |
4.4 |
Mb |
10.740 |
95.540 |
024.0 |
Andaman Sea Ridge |
GFZ |
|
26july09 |
16:12:54 |
4.5 |
Mb |
10.840 |
94.480 |
025.0 |
Andaman Sea Ridge |
GFZ |
|
26july09 |
15:51:00 |
4.9 |
Mb |
10.494 |
94.239 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
15:27:04 |
5.2 |
Mb |
11.862 |
94.351 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
14:58:13 |
4.9 |
Mb |
10.601 |
94.115 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
14:26:57 |
4.8 |
Mb |
11.010 |
95.000 |
033.0 |
Andaman Sea Ridge |
GSR |
|
26july09 |
13:48:51 |
4.9 |
Mb |
10.495 |
93.892 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
13:29:14 |
5.1 |
Mb |
10.666 |
94.296 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
13:19:37 |
5.0 |
Mb |
10.720 |
94.310 |
033.0 |
Andaman Sea Ridge |
GSR |
|
26july09 |
12:48:36 |
4.9 |
Mb |
10.696 |
94.314 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
12:34:33 |
4.8 |
Mb |
10.701 |
94.380 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
12:25:51 |
4.8 |
Mb |
10.555 |
94.075 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
12:14:28 |
4.4 |
Mb |
10.820 |
94.380 |
020.0 |
Andaman Sea Ridge |
GFZ |
|
26july09 |
11:55:44 |
4.8 |
Mb |
10.615 |
94.244 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
11:18:52 |
4.5 |
Mb |
10.828 |
94.493 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
10:58:01 |
4.6 |
Mb |
10.684 |
94.367 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
10:42:29 |
4.7 |
Mb |
10.839 |
94.404 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
10:14:16 |
4.9 |
Mb |
10.724 |
94.379 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
09:40:26 |
4.8 |
Mb |
10.651 |
94.414 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
09:06:47 |
4.6 |
Mb |
11.129 |
94.894 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
08:40:56 |
4.8 |
Mb |
10.741 |
94.420 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
08:11:16 |
4.7 |
Mb |
10.725 |
94.347 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
07:40:13 |
4.8 |
Mb |
10.736 |
94.288 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
06:54:48 |
4.8 |
Mb |
10.887 |
94.493 |
010.0 |
Andaman Sea Ridge |
NEIC |
|
26july09 |
06:49:25 |
4.8 |
Mb |
10.820 |
94.360 |
019.0 |
Andaman Sea Ridge |
GFZ |
|
26july09 |
06:45:37 |
4.7 |
Mb |
10.891 |
94.480 |
010.0 |
Andaman Sea Ridge |
NEIC |
Earthquakes swarms can be defined as a series of earthquakes in
the same magnitude range that are closely spaced in time and
originating in the same region but devoid of a mainshock
(principal large event). They can last from as
little as a few
hours to as long as several months (eg. Matsushiro, Japan,
1965-1966). Swarms can be precursory or non-precursory but
establishing either is only feasible in hindsight. Earthquake
swarms have occurred in other parts of the
Indian mainland
including
Nanded (Maharashtra) in
2006-2008,
Jind (Haryana) in 2003,
Bhavnagar (Gujarat) in 2000. |
