Earthquake Sequence in Western Afghanistan in October 2023 (Quantectum’s Report)

Since October 2023 we have observed an increased seismic sequence in western Afghanistan, which led to four large earthquakes of magnitude 6.3 and many moderate aftershocks. This seismic sequence in western Afghanistan, which started on the 7^th of October 2023, caused many challenges and difficulties for local communities. From structural damage to infrastructure and the displacement of families to the looming threat of aftershocks, this series of earthquakes has tested the resilience and adaptability of those living in the affected areas.

In this process, the Quantectum Global Operations Center has remained steadfast in its commitment to monitor and analyze the evolving seismic situation. The results of our diligent observations and assessments are presented in this comprehensive report, to shed light on the impact of these seismic events.

Earthquakes in October 2023 in Western Afghanistan

From the 7^th of October 2023 until the 20^th of October 2023, western Afghanistan experienced 41 detected earthquakes. Among them, four were of magnitude 6.3, seven were between magnitudes 5.0 and 6.0, and 32 were between magnitudes 4.0 and 5.0, according to the EMSC.

The first magnitude 6.3 earthquake hit the Herat region on the 7^th of October at 11:11 local time. It occurred along the Herat fault and it continued toward the west. The other three of the magnitude 6.3 earthquakes and many other weak-to-moderate events also occurred in the same area. The figure below shows the history of the seismic activity in western Afghanistan from October 2018 to the 18^th of October 2023. It is noticeable that the fault system was characterized by quite high seismic activity but the earthquakes’ magnitudes did not often reach or exceed a magnitude of 5.0 before this swarm.

Picture 1: History of seismic activity in western Afghanistan from October 2018 to the 18^th of October. 2023.

Stress and Shear Traction Field Analysis

In seismology, shear stress and shear traction field analysis are crucial for understanding the dynamics of tectonic plate interactions, the buildup of the shear stress in the Earth's crust, the mechanisms of earthquakes, and consequently earthquake forecasting.

The above-mentioned Herat Fault is a major dextral strike-slip fault, oriented in a northwest-to-southeast direction. However, the October earthquakes indicate the reverse reactivation of the fault system. This is shown in the next figure, which demonstrates that these seismic events are related to a north-to-south-oriented compression (as shown by red arrows and beachballs on the map of the study area), coupling with an increasing tectonic traction field (shown in the graph on the left bottom with red, green and black curves).

The determined focal mechanism solutions were thrust faults in the cases of all the earthquakes above a magnitude of 60, represented by red and white beachballs on the following map. Different colors of beachballs on the figure correspond to different focal mechanisms between the 1st November 2022 and the 1st November 2023, showing that the Afghanistan earthquakes were related to thrust faultings.

More explanations about Quantectum’s stress field analysis are available here, in the chapter on Global Tectonic Stress.

Picture 2: Visual representation of fault system in the time of October 2023 in western Afghanistan.

T-synchronizations

Quantectum’s earthquake forecasting models approach is rooted in a process in which earthquakes follow a geometric or periodic pattern, underpinned by the Theory of Chaotic Synchronizations. This innovative approach leverages the temporal evolution of chaotic synchronizations along prominent fault lines, such as the Herat fault.

The results of this analysis are presented in a comprehensive and informative manner, with a focus on statistical interpretation through the use of Molchan diagrams. The Molchan test is an alarm-based approach through which the rates of missed earthquakes and the spatio-temporal variability of the alarms can be studied.

In the following figure, the left side provides a visual representation of the temporal development of chaotic synchronizations along the Herat fault. This dynamic depiction of the synchronization patterns helps in understanding how stress and energy may be accumulating and releasing along this fault, potentially leading to seismic events. The visualization aids in identifying trends and patterns in earthquake occurrence.

On the right side, we present the Molchan diagram, which offers valuable insights into the statistical interpretation of the modeling results. This diagram serves as a crucial tool for assessing the success of the earthquake forecasting system. By examining the Molchan diagram, researchers and seismologists can verify the accuracy and reliability of the issued alarms and forecasts, or in other words, it gives information about the success of the issued alarms. For more information see here.

Based on the analysis of temporal development and Molchan diagram we can see that earthquakes in western Afghanistan were related to strong time-synchronization or instabilities which will continue by December 2023.

Picture 3: Temporal development of chaotic synchronizations along the Herat fault (left) and Molchan diagram (right).

The next figure illustrates the analysis of the temporal development of chaotic synchronizations along the Herat fault but in the time from February 2022 to December 2024 in western Afghanistan. The local maxima on the graph correspond to the periods of significant T-synchronizations. It is visible that the next moderate synchronization period will develop in March 2024 and then in September 2024. At that time the Herat fault will be unstable and prone to fluctuations of the shear stress and shear tractions.

Picture 4: Analysis of the temporal development of chaotic synchronizations along the Herat fault from February 2022 to December 2024 in western Afghanistan.

Critical Triggering Potential

The critical triggering potential is a parameter that is applicable to estimate the likelihood of earthquake triggering across various magnitudes (on the graph below, different colors belong to different magnitudes), calculated based on the shear traction and fault instability (T-synchronizations) models.

During the October earthquake sequence in western Afghanistan, the elevated critical potential was particularly notable during the occurrence of the M6.3 earthquake on the 11^th of October 2023. This surge in critical potential can be primarily attributed to the heightened shear traction field, a direct consequence of tectonic waves coursing through the epicentral region.

The map below graphically represents the distribution of shear traction values with the marked event signifying the most recent significant earthquake that occurred on the 15^th of October, 2023. On the left side, the graph of the critical potential is displayed with the earthquake swarm starting on the 7^th of October 2023.  Based on this chart, the Afghanistan earthquakes occurred at the edge of the high shear traction cloud.

Picture 5: Distribution of shear traction values in western Afghanistan and graph of the critical potential is on the left, displaying the current earthquakes in Western Afghanistan (red and black columns).

Dynamic Traction Field Analysis

The area encompassing the earthquake in western Afghanistan has been in a state of heightened dynamic traction due to the relentless propagation of active tectonic waves. This continuous propagation is a sign of elevated seismic activity in the area. In simpler terms, as the seismic events along these corresponding tectonic waves increase in frequency and intensity, so too do the tectonic tractions that they generate.

This increase in tectonic traction is a clear indication of the increasing geological stress within the Earth's crust, suggesting that the region is becoming more susceptible to seismic disturbances. The interplay between tectonic forces and seismic events serves as a reminder of the ever-present potential for significant seismic activity in the affected area, necessitating vigilance and preparedness on the part of both scientists and local communities. Understanding these dynamics is crucial for devising effective strategies to mitigate the impact of earthquakes and protect the well-being of the populace in earthquake-prone regions.

Picture 6: Heightened dynamic traction due to the relentless propagation of tectonic waves in western Afghanistan.

Earthquake Sensors in Afghanistan

Afghanistan doesn't provide much information about earthquakes because the country did not experience enhanced seismic activity before these large events and they don't have many earthquake sensors. The lack of earthquake sensors is a problem because the country is located in an area where earthquakes can occur, but there aren't enough tools to study and forecast them. This can be seen on the USGS earthquake map which consists of information on earthquakes and tectonic setting in the Middle East, available here.

Conclusion

Quantectum will continue the careful and close monitoring of the region due to the expected continued aftershocks. Earthquakes, including aftershocks in the epicentral region, are expected to occur in March and September 2024 and will be connected to the development of the significant chaotic synchronizations along the Herat fault as well as the possible fluctuations of the tectonic tractions and stresses in the area.

Sources:
1) Žalohar, J., & Vrabec, M. (2007). Paleostress analysis of heterogeneous fault-slip data: the Gauss method. Journal of Structural Geology, 29(11), 1798-1810.
2) Žalohar, J., & Vrabec, M. (2008). Combined kinematic and paleostress analysis of fault-slip data: The Multiple-slip method. Journal of Structural Geology, 30(12), 1603-1613.