Animations from: S. Toda, R. S. Stein, K. Richards-Dinger and S. Bozkurt, Forecasting the evolution of seismicity in southern California: Animations built on earthquake stress transfer, J. Geophys. Res., Vol. 110, B05S16, doi:10.1029/2004JB003415, 2005.

Southern California seismicity, 1981-2004, in 4-months increments

Observed seismicity in 4-month time increments in a 300 x 310 km area of southern California centered on the 1992 Landers rupture. When opened in Flash Player, choose ‘Full screen’ in the ‘View’ menu if the image does not fill the screen. Red lines in the time scale at left mark the times of mainshocks; their epicenters (stars) and fault ruptures (bold red lines) briefly appear. While the background seismicity pattern is remarkably stable, it is punctuated by mainshocks and their rapidly decaying aftershocks. Because the majority of aftershocks occur in the first frame after each main shock, it is difficult to judge how aftershock zones grow, migrate, or change.
Animation by: Serkan Bozkurt

Observed seismicity in log-time increments. So that each frame contains roughly the same number of aftershocks, the duration of each frame lengthens with time after a mainshock in half-decibel log-time increments (0.09, 0.28, 0.89, 2.82 days, etc). Frame 1 shows the cumulative seismicity in the 4-year interval be used to approximate the background seismicity for Animation 3. The time increments reset to 0.09 days (3 hr 8 min) after each M≥6 mainshock. The animation pauses between the Landers and Big Bear mainshocks so that the immediate off-fault seismicity can be examined; click the ‘play button’ to continue. During short periods, seismicity is dominated by aftershocks; for long time periods, the background seismicity becomes appreciable. There are many surprising features of the aftershock process that the rate/state Coulomb model seeks to capture. Examples include the westward expansion of the North Palm Springs aftershock zone; the north, east, and southward expansion of the Joshua Tree aftershock zone; the off-fault clusters of Landers aftershocks, and the jet of seismicity extending from the Hector Mine shock 140 km to southwest, in frames 32-35.
Animation by: Serkan Bozkurt

Expected vs. observed seismicity in log-time increments. Frame sequencing, labeling and controls are the same as Animation 2. The expected earthquake density (scale bar at right) is calculated from the rate/state stress transfer model. The smoothed 1981-1986 seismicity is used to approximate the long-term background rate, as shown in frame 1. In each frame, the expected number of earthquakes due to the background alone is shown in the lower right. The fading effects of the stress transferred by each M≥6 mainshock results in the difference between the expected seismicity main frame and the lower right frame. Such differences are pronounced, for example, in frames 19, 29, 34, and 39. The expansion of the aftershock zones of the North Palm Springs (frames 2-8) and Joshua Tree (frames 12-17) shocks resembles the rate/state model. Most immediate aftershocks of Landers lie in areas of expected high seismicity rate (frame 19). Two weeks later (frame 24), clusters of aftershocks appear where stress increases coincide with areas of high background seismicity. The jet of shocks extending southwest of the Hector Mine fault corresponds to sites of expected seismicity caused by the interaction of the Hector Mine shock with the decaying effects of the Landers, Big Bear, and North Palm Springs mainshocks in regions of high background seismicity. The effect of Coulomb stress shadows can be seen by the absence of earthquakes in regions that formerly were seismically active.
Animation by: Serkan Bozkurt

When a fault fails during an earthquake, it modifies the stress field in its surroundings. The modification of the stress pattern can give a rough idea of where the next shocks are more likely occur. This animation simply adds the Coulomb stress change for successive earthquakes to show how the stress built up for the seven earthquakes that struck the Mojave desert (Southern California) since 1975.
Animation by: Thomas Dewez and Serkan Bozkurt

The following animations relate to our work on the North Anatolian Fault in Turkey, but apply as well to the San Andreas Fault, its sister in California.

Very much like the San Andreas in California, the North Anatolian is a 'strike-slip' fault. That is a fault that slip laterally. The bulk of Turkey, south of the North Anatolian Fault is forcing its way to the West, while the rest of the Eurasian plate (Black Sea and former USSR republics) drifts towards the East.

Since the beginning of instrumental records in the first half of the1900s, the North Anatolian fault has ruptured 1000 km, nearly its entire length from the Iranian border on the East to the Marmara Sea in the West. This earthquake migration does not appear random. Indeed, the "coulomb stress change" associated with each individual medium size earthquake that occurred since 1900 increases where the next earthquake occurred.

In the Marmara Sea, the fault rupture is less simple. But the North Anatolian Fault roughly failed from West to East, bringing the next earthquake closer to Istanbul. In the present situation, Istanbul sits in the 'Red Zone' and this is where the next large earthquake could occur next.

A more detailed explanation about the theory behind the stress-triggering process is given in the Stress-triggering and Probability section of this web site.

Check also:

T. Parsons, S. Toda, R. S. Stein, A. Barka and J. H. Dieterich,

Heightened odds of large earthquakes near Istanbul: An interaction-based probability calculation, Science, 288, pp. 661-665, 2000.

[Online article] [Printable article (213kb)

Animations by: Rachel Margrett, Serkan Bozkurt and Ross Stein.