Earthquake Report for November 27, 2005: West of Qeshm (Persian Gulf)

At 13:52 (local time) an earthquake with ML=5.6 on the Richter scale occurred 44 km west of Qeshm in the Persian Gulf and 57 km southwest of Bandar Abbas. (Figure 1) The magnitude of this earthquake according to the body wave scale is estimated at Mb=6.2. This seismic event has been recorded at all 14 broad band seismic stations of the Iranian National Broad-Band Seismic Network (INSN) at IIEES (Figure 2). Waveforms of this earthquake can be downloaded from the IIEES website. According to the recorded seismograms, the location of this earthquake is at 26.87˚N and 55.83˚E. Having been recorded by the Iranian National Broad-Band Seismic Network (INSN) at IIEES, over 400 aftershocks have followed the main earthquake in this region with 36 aftershocks of magnitude greater than 2.5 (Figure 3 and Table 1). The biggest aftershock was of Mb=5.9 which occurred at 8 p.m. the same day. So far this earthquake has had 10 casualties and over 100 injured. The earthquake has destroyed 12 villages including Tonban, Ramekan, Gavarzin, Khaledin, Direstan, Kushe, Karavan, Turyan, Tom senati, Gorbehdan, Ziranag and Giahdan.

Figure (1): Epicenter of Nov. 27, 2005 West of Qeshm earthquake

Figure (2): Recorded seismograms of Qeshm Earthquake (Persian Gulf) by the Iranian National Broad-Band Seismic Network (INSN) of IIEES.

 

Table (1): Aftershocks of Qeshm Earthquake (Persian Gulf)

 

 

Figure (3): Distribution of aftershocks recorded until Nov. 29, 2005.

 

Analysis of Bandar Abbas region’s Seismicity.

Seismic analysis of the 52 km range of the earthquake shows over 80 earthquakes having occurred with a magnitude greater than 5 in the last 100 years, the biggest of which was the March 21, 1977 earthquake with Ms=6.9 in northern Bandar Abbas (Figure 4).

Analysis of focal mechanisms of the main earthquakes in the Bandar Abbas region are displayed in figure (5).

Geologically, the epicenter of the may shock is located at the farthest Northern plate of Saudi Arabia and southern border of Zagros deformation. Focal mechanism of the earthquake is thrusting. (Figure 6)

 

Figure (4): Instrumental earthquakes bigger than 5 in the region of Qeshm.

Figure (5): Focal mechanisms of the main earthquakes in the Bandar Abbas region.

Figure (6): Focal mechanisms of Qeshm Earthquake (Persian Gulf) determined by USGS and Harvard.

Figure (7): Satellite view of the region.

Figure (8): Satellite view of the earthquake epicenter.

Table (2): List of historical earthquakes in Qeshm Island.

 

Figure (9): Focal depth of historical earthquakes in Qeshm Island.

Prior to this date, the last earthquakes having occurred in this region go back to 2004 with magnitude of 2.6 and 3.2 and 2005 with magnitude of 3.6. Characteristics of these earthquakes are shown in Table (2) and their focal depths may be seen in Figure (7).

 

Table (3): Earthquakes occurring in Qeshm Island during the past 2 years.

 

Figure (10): Focal depth of earthquakes occurring in Qeshm Island in the year 2004.