Damavand-Jajarm (East Tehran) Monitor

We present the up-to-date seismicity associated with the Damavand-Jajarm system as a series of space-time sections. The aim is to reveal the hidden orders and to facilitate prompt interpretation. The earthquake data is obtained from the IRSC and the ISC databases every minute. With new earthquakes the figures and maps are updated immediately; otherwise, they are regenerated every hour. The following points should be considered regarding the images.

1. There are 8 figures showing time-space sections of seismicity for different periods. Earthquakes are projected on the line segments that represent the Damavand-Jajarm system.
2. The yellow line segments, ‘W-E’, on the maps show the section. Earthquakes within a 20 km range are projected in the section.
3. For each figure X, there are 3 associated illustrations with a corresponding period. Xa shows the seismicity for the whole region, while Xb displays the events in the window around the section. Figure Xc shows the depth distribution of events along the section. Their links are given below each figure.
4. The thick red line segments that are labeled D, E, F, G, H, I, J, and K on the maps and also along the right axis of each figure represent seismic gaps.
5. The thick magenta line segment along the left axis of the figures (195-350 km) shows parts of the section that falls within the macroseismic area, black ellipse on the maps, of the 22 December 0856 (M~7.9) earthquake (Ambraseys and Melville, 2005).
6. The extensive seismicity along segments E, G, and H represents the release of a tiny fraction of the stored energy.
7. A proper example for the observed seismicity along segments E, G, and H is the decades of seismicity prior to the 17 August 1999 (Mw 7.6) Izmit earthquake, which is best displayed in Figure 7 of the Main Marmara Fault Monitor (MMF).
8. The seismicity prior to the 1999 Izmit earthquake extends to depths of 25 to 30 km (Figure 6c and 7c on the MMF page), while for the post-earthquake period the main seismicity remains shallower than 15 km (Figure 5c on the MMF page). This observation is physically meaningful; by approaching the end of a seismic cycle the whole fault plane undergoes brittle failure, even the deeper parts that usually behave semi-brittly due to high pressure and high temperature.
9. By analogy to the 1999 Izmit case, Figure 5c indicates that segments G and H are maturer than the other segments in the section.
10. Segment E seems less mature compared to segments G and H and maturer compared to the other segments.
11. Segment G alone, with a length of about 145 km, is capable of generating an earthquake similar to the 22 December 0856 (M~7.9) event.
12. The pale-green polygon next to gap D shows eastern part of Tehran.
13. The earthquake data for the post-2006 period is obtained from the IRSC catalog, while the ISC database is the data source for earlier times.

Click to open map 1a, map 1b or figure 1c

Click to open map 2a, map 2b or figure 2c

Click to open map 3a, map 3b or figure 3c

Click to open map 4a, map 4b or figure 4c

Click to open map 5a, map 5b or figure 5c

Click to open map 6a, map 6b or figure 6c

Click to open map 7a, map 7b or figure 7c

Click to open map 8a, map 8b or figure 8c

Acknowledgment

The earthquake data for this project is obtained from (i) the “Iranian Seismological Center” (IRSC) of the Institute of Geophysics, University of  Tehran and (ii) the International Seismological Center (ISC). We appreciate these institutions for the release of their products to the public. The figures are produced by using the “Generic Mapping Tool” (GMT) and we thank the developers of the software (Wessel et al., 2013).

References

• Ambraseys NN, Melville CP. A History of Persian Earthquakes. Cambridge university press; 2005.
• Wessel P, Smith WH, Scharroo R, Luis J, Wobbe F. Generic mapping tools: improved version released. Eos, Transactions American Geophysical Union. 2013;94:409–410.