At 4:17am local Turkey time (i.e. 17:35 Coordinated Universal Time) on 6 February 2023, a magnitude 7.8 earthquake at a very shallow depth of 17.9 km occurred about 26 km west of Nurdağı city with the population of about 41,000 and 47 km north west of Kahramanmaraş city (population of over 1 million people), in southern Türkiye.

Another magnitude 7.5 earthquake happened 9 hours later near Ekinözü, approximately 100km from the initial earthquake. The intensity of the first earthquake, which was IX (known as a violent earthquake) indicates that unfortunately heavy damage to structures, buildings and infrastructure will be expected and the peak ground velocities and accelerations in excess of 86 cm/s and 0.8g are expected, respectively.

The energy released due to this 7.8 magnitude earthquake in Türkiye is comparable to about 500 atomic bombs. Since the occurrence of the initial violent earthquake, over 50 aftershocks with magnitudes between 4.0 and 6.7 have been recorded in the same region in the vicinity of major cities of Adiyaman and Gaziantep.

In the vicinity of the epicentre of the this earthquake, three major African, Arabian and Anatolian plates intersect and it is expected about approximately 200km long fault was ruptured in the this magnitude 7.8 earthquake. The movement rate between the Anatolian and Arabian plates is estimated to be about 20 mm/year in a north-eastern direction. In the close vicinity of this recent earthquake, there is a major fault line known as East Anatolian Fault. Indeed, East Anatolian Fault, which is between the Anatolian and the Arabian tectonic plates, is composed of a series of parallel lateral strike-slip faults. This region is one of the most active seismic zones in the world. Indeed 84 years ago, the 1939 Erzincan earthquake along East Anatolian Fault with exactly the same magnitude of 7.8 resulted in over 30,000 dead and about 100,000 injured.

Various regions in Kahramanmaraş city are composed of shallow marine deposits underlain by limestone and claystone deposits. What is particularly concerning in these areas is the potential for liquefaction. Considering the presence of alluvial deposits, composed of saturated mixture of fine- and coarse-grained soils, buildings and roads sinking into the ground because of ground liquefaction, and total collapse of building and structures because of foundation failure are very likely.

As countries come together to provide an international response to the catastrophic earthquakes in Türkiye and Syria it is helpful to review the lessons from past earthquake disasters. The cardinal lesson of past disasters is that the international response needs to be carefully considered and targeted, to ensure that the resources provided are truly needed, and to avoid clogging supply lines, including ports and airports, with unnecessary, or frankly inappropriate, goods and services.  

This is especially the case in earthquake disasters, where damage to roads and other infrastructure challenges the effective delivery of aid. Affected communities cannot afford the additional complication of unwanted donations which typically clog transport hubs and need to be disposed of after the event. The best international support is usually financial assistance, whereby funds can be spent locally to provide needed forms of assistance, and, importantly, assist in the re-establishment of business and employment because money is being spent locally (or at least regionally) on goods and services provided by the affected community. 

In the initial stages after an earthquake, the majority of victims are rescued by relatives and neighbours. The international media is often focussed on the work of international urban search and rescue (UDSAR) teams. We know that foreign USAR teams usually arrive too late to make a significant contribution to lives saved. In any case, in an event of such scale and geographic spread, it is unlikely that a USAR team will be  in the right place when needed. The most effective strategy to ensure lives are saved post event, is preparation and community resilience building prior to the event. This can take various forms, for example, improved building practices, and comprehensive community education, especially for rescue and immediate first aid.

The recent earthquake in Türkiye is believed to be associated with the East Anatolian fault belt located in the northern region of the Arabian Plate. This fault belt is considered a significant seismic zone, with a high frequency of earthquakes occurring along it annually. Today's primary earthquake had a magnitude of 7.8 on the Richter scale, which can result in hazardous phenomena such as landslides and soil liquefaction. According to the USGS, a secondary earthquake of magnitude 6.7 on the Richter scale, occurred shortly thereafter in close proximity to the epicentre of the primary event, and at a shallower depth of 12 km. This earthquake, albeit less intense, could still cause significant damage. In addition, five smaller aftershocks ranging from 4.8 to 5.6 on the Richter scale, were recorded in the vicinity of the two main earthquakes' epicentres, within an hour of the occurrence of the second earthquake.

It is worth noting that a similar earthquake, with a magnitude of 7.1 on the Richter scale and a depth of 16 km, had taken place along the same fault belt in 2011 in the city of Van, resulting in over 600 fatalities and 4000 injuries.

In light of the aforementioned, it is imperative for all relevant organizations and individuals to remain vigilant and prepared for the possibility of further earthquakes in the coming days. Furthermore, given the magnitude of the recent event, it is of utmost importance to provide adequate support and relief to affected populations.

The sequence of earthquakes in Türkiye have had such devastating impact due to a number of factors. The magnitude of the first event was around ten times larger than anything experienced before in that area, and the fact that it was relatively shallow (at 17km deep) meant that more of its energy reached the surface. The proximity of the epicentre to highly populated areas, at a time of day when most people were asleep in their homes and less able to react quickly, also added to the toll on the community. The significant magnitude aftershocks that started only minutes after the main shock also contributed to the destruction of already compromised buildings. An aftershock of similar magnitude to the main shock was also a rare and unfortunate occurrence, spreading the impact further afield. Our hearts go out to the people affected, and to those working to rescue others in very difficult conditions.

While the situation is still unfolding it is clear that the magnitude 7.8 earthquake in Türkiye and Syria is a significantly devastating event. There are several factors that make some earthquakes particularly devastating:

1. A large magnitude indicates more energy released and more intense seismic shaking
2. When the earthquake occurs at a shallow depth in the crust 
3. When it occurs close to densely populated areas 
4. When the buildings in those areas have not been constructed to withstand seismic shaking of such intensity.

Unfortunately the recent M7.8 event in Türkiye/Syria appears to be the perfect storm of all these factors. The USGS (United States Geological Survey) reports the earthquake originated at a relatively shallow depth of 17.9 km below the surface and that more than 5 million people live in the zone of “Very Strong” shaking or higher (i.e. level VII or higher on the Modified Mercalli Intensity scale which is used by seismologists to quantify the level of shaking experienced during an earthquake).

The 7.8 earthquake in Türkiye and Syria, termed the Kahramanmaras Earthquake, is definitely of a very high magnitude, but it is not only the magnitude of the natural hazard that can cause such devastation – when the hazard met conditions of vulnerability, the disaster resulted. These conditions include the type of buildings and the timing of the earthquake, among other factors. The timing of the earthquake was unfortunate, at 4:17am in the early morning when people were sleeping and crushed by collapsing structures. 

It is uncertain to what extent buildings there were built to earthquake codes; given that the last earthquake in the region was more than a 100 years ago, there is hardly any living memory that can make the institutional case to implement and enforce earthquake-safe building codes. In other words, a local culture of safety was lacking. Most of the buildings there are of monolithic, masonry construction, which is vulnerable to the lateral stress (shaking) caused by the earthquake. Additionally, widespread multi-storey buildings there in a context of high-density population created more risk than low-rise, low-density settlements as in countries like Australia. Furthermore, the overall quality of construction is uncertain as well as the extent of professional support for it.

Recovery will be a protracted and difficult process, especially because the region is in a conflict zone that will deter international assistance. The huge amount of international assistance that will be needed will face challenges in the current global economic downturn due to the war in Ukraine. The key issue to hope for is that the recovery follows the “building back better” approach so that future risk is reduced.

The large M7.8 earthquake that occurred on February 6th 2023 was one of the largest shallow depth earthquakes to have happened in the region in the last few hundred years. This mainshock was a strike-slip type earthquake that occurred in the East Anatolian Fault Zone. This complex, seismically active region accommodates the movement of three tectonic plates.  

This large earthquake was then followed by a series of large aftershocks including the M6.7 just 11 minutes later and the M7.5 about nine hours later. Due to the size and shallow depth, the event will cause severe ground shaking. As the location of the earthquake sequence is close to large population centres, there will be significant and widespread damage.

Large earthquakes are much more common near plate boundaries (such as the Pacific Ring of Fire) and continental collision zones which includes the Anatolian Fault systems that ruptured this week. The plates collide because of slow, relentless tectonic motions that gradually build up stress over many hundreds or thousands of years. The stress is released in a matter of seconds when an earthquake occurs. Not all of the stress is released so there will be aftershocks and there is still a danger of further large earthquakes on nearby faults.

We know that Australia is far from any plate boundaries and that does mean that our risk is quite a bit lower but earthquakes can and do happen here. Australians do need to be aware of what to do in an earthquake because we love to travel on holiday or to visit friends and family in areas where earthquakes are common. Know that you need to “duck and cover” during shaking, and to seek higher ground if there is any risk at all of a tsunami.

The earthquake yesterday in Türkiye and Syria once again shows the global dangers of earthquakes. The region impacted is located on a tectonic plate boundary in which large earthquakes occur.

Australia is located away from tectonic plate boundaries; however, we are more vulnerable to earthquakes than one would expect due to how our buildings are constructed and the concentration of our population.

Earthquake was not fully recognised in Australian building design until the mid-1990s which means that we have a large amount of buildings which are structurally unable to withstand even moderate seismic shaking – a prime example being the 1989 Newcastle earthquake, one of the costliest natural hazards in Australia.

Research has shown that enhancing the safety of our buildings in Australia is critical to keeping Australians safe from earthquakes. We can’t completely stop building damage but strengthening buildings is the key to our safety – building collapses historically lead to the most fatalities.