Seismic rupture patterns reveal that the Mamara fault directs a considerable seismic energy towards Istanbul

New analysis of seismic rupture directness provides important insights for earthquake risk and risk assessments, particularly for the major Marmara fault near Istanbul, Turkier, in the western part of the country.

Based on the correlation between rupture directionality and the direction of transported seismic energy, a team of researchers led by Dr. Xiang Cheng and Professor Patricia Martínez-Garzón, has shown that Quakes in the Marmara region transports particularly energy.

Their research has been published in the journal Geophysical Research Letters. They analyzed 31 well-constrained ML≥3.5 earthquakes in this region. The key patterns announced could affect preparation for future seismic events in one of the world’s most populous cities.

Earthquakes are natural phenomena and can have devastating effects, especially in densely populated areas. In particular, understanding the behavior of these seismic events is important to mitigate risk and enhance preparation.

In recent years, it has been revealed that energy transported by seismic waves can become stronger in a given direction (in the direction of heartbeat rupture), and can have important consequences for potential damage to the population.

Analysis of the Marmara Sea based on small earthquakes and modeling

A team of researchers led by Dr. Cheng and Professor Martínez-Garzón of the GFZ Helmholtz Geosciences Center in Potsdam, Germany, investigated such directional effects. They analyzed a well-constrained earthquake of 31 with magnitude ML > 3.5 in the Marmara Sea, west of the enormity of Istanbul. Smaller earthquakes occur more frequently, making them a blueprint for the “big things” that are more rare, but they are blueprints for the “big things” that have greater meaning.

In their study, the researchers compared the modeled and measured waveforms to calculate the source mechanism, measured the duration of the earthquake in different directions, and estimated the indicator effect of moderate earthquakes in the Istanbul-Marmara region.

The findings reveal that most of the studied earthquakes beneath the Marmara Sea, west of Istanbul, exhibit primarily eastward ruptures. This increases the energy directed towards the big cities. The median direct trend of 85° from the north is closely aligned with the main Marmara fault strike.

“The trend in this direction suggests that ground shaking is more pronounced in Istanbul during such seismic events,” says Dr. Xiang Chen, the first author of the study and postdock scientist at GFZ.

This information is particularly important as the main Marmara faults are considered to be delayed in the seismic cycle. This means that a major earthquake is delayed. This study does not alleviate concerns about the implications of major earthquakes in this region.

“Depending on where future major earthquakes will nucleate, these asymmetric rupture patterns could lead to increased underground movement towards the urban centre of Istanbul,” said Professor Patricia Martinez Garzon, working group leader for the geological and scientific drilling and corresponding authors of GFZ Section 4.2.

Recommended considerations for earthquake hazard maps

When estimating seismic hazard maps for a particular area, rupture directivity, such as the priority direction in which the earthquake emits energy, has not yet been taken into consideration.

“We hope to include indicator effects in next-generation seismic hazard maps used in seismic engineering, and these results are fundamental to enabling this development.”

Measured data from this study were partially distributed by the Plate Boundary Observatory (Gonaf), which has been operating in the Marmara region since 2015, in collaboration with the President of Disaster and Emergency Management (AFAD). It consists of various types of instrumentation, including seismometers installed in boreholes to accurately monitor and measure seismic activity in the area.

“The key objective of our observation deck is to better monitor small and medium earthquakes in the Marmara region and prepare as best as possible when major earthquakes burst near Istanbul,” adds Professor Marco Bornhoff, a leading scientist in Section 4.2 of Earth Machinery and Scientific Excavation, Scientific Excavation and Gonav Earth Observation.

Urban planning and impact on population protection

The implications of this study underscore the need for urban planners, policymakers and emergency response coordinators to incorporate detailed earthquake risk assessments into planning frameworks.

“Evaluating the potential earthquake impacts based on improved scientific methodology can significantly increase the resilience of Istanbul’s infrastructure and community,” emphasizes Patricia Martinez Garzon.

This study not only highlights seismic behavior at the major Marmara fault near Istanbul, but also serves as a key reminder of the ongoing threat that earthquakes pose to urban environments around the world. As population density and infrastructure challenges make cities more vulnerable, understanding the nuances of seismic activity remains essential to protecting regions.