Rudbar-Taleghan (West Tehran) Monitor

We present the up-to-date seismicity associated with the Rudbar-Taleghan 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 Rudbar-Taleghan system.
  2. The yellow line segments, ‘SE-NW’, 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 A, B, and C on the maps and also along the right axis of each figure represent seismic gaps.
  5. The thick magenta line segments along the left axis or within the figures, (20-130 km, 140-230 km, and 265-350 km), in turn, show the projection of the faults along the diagonal of the macroseismic area of the 23 February 0958 (M~7.7), macroseismic area of 20 April 1608 (M~7.6) (Ambraseys and Melville, 2005) and the surface ruptures of the 20 June 1990 Rudbar (M 7.4) earthquakes.
  6. A large number of the current seismicity along the system is clustered at the southeastern end of the 1990 surface rupture (~250 km zone). The majority of these events show a reverse mechanism with almost N-S nodal trends, similar to that of the 21 June 1990 aftershock (shown on all maps).
  7. A restraining step-over that stopped the 1990 rupture is behind the above-mentioned reverse events. The processes of these reverse events started immediately after the stopping of the 1990 rupture, as indicated by the occurrence of the largest aftershock of the event on 21 June 1990.
  8. The above two points indicate that the system tries to continue its SE-ward rupture since its stop in 1990.
  9. The macroseismic areas of the 0958 and 1608 earthquakes correspond with the extensive gap in the seismicity of the Alborz ranges, as is seen in maps 5a to 8a.
  10. The pale-green polygon next to gap C shows the extents of Tehran.
  11. 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.
Elements and details that may become unrecognizable due to dense seismicity or background color of the maps.
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.