*AYNI FAY ÜZERİNDE BU BÜYÜKLÜKTE DEPREM OLMADI*

ABD'li deprem uzmanı: Aynı fay üzerinde bu büyüklükte deprem olmadığını söyledi.

2023-02-10 16:25:51 | Son Güncelleme: 2023-02-10 17:04:07

New York'taki Cornell Üniversitesi Jeoloji Bölümü'nden Doç. Dr. Judith Hubbard, Türkiye'de binlerce insanın ölümüne neden olan ölümcül depremler hakkında konuştu. Uzman, böyle bir depremin olağanüstü olduğunu söyledi.

 

*US Earthquake Expert Spoke*

No Earthquake Of This Magnitude Has Occurred On The Same FaultScience  

Department of Geology at Cornell University in New York, Assoc. Dr. Judith Hubbard spoke about the deadly earthquakes in Türkiye that killed thousands of people. The expert said that such an earthquake is extraordinary.

Doing earthquake research in the Department of Geology at Cornell University in New York, Assoc. Dr. Judith Hubbard analyzed (according to measurements in the USA) 7.8 and 7.5 earthquakes in Türkiye.

Assoc. Dr. Hubbard stated that he has been conducting earthquake research in various parts of the world for 20 years. Hubbard, in his studies, described the earthquakes in the southeastern region of Türkiye as "more complex than many earthquakes that occurred". Hubbard contunued with the words, “So many different faults seem to have ruptured, and then what I think everybody noticed was utter destruction.”

 

*LARGE EARTHQUAKES ARE ALWAYS A SURPRISE*

Stating that the earthquakes were always unexpected, the US academic said that the Türkiye-centered earthquake on Monday was not much different: 

“Large earthquakes are always a surprise — and always inevitable. Monday’s deadly events in Türkiye and Syria are no different. The fault system that caused them and the region’s seismicity are well documented from painstaking field studies, historical records and geophysical observations over many decades. Yet no seismologist could have predicted the exact location, time and magnitude of this week’s quakes.”

"The footage of the destruction of buildings is so tragic... And it remains very unique compared to previous earthquakes. So the combination of the extent of the destruction and the visibility of the destruction is really shocking,"  Hubbard  said.

 

 

HE SAID THESE EARTHQUAKEES WERE 'EXTRAORDINARY'

Judith Hubbard, who made a statement about the earthquake that affected more than 13 million people in 10 provinces in Türkiye and in northern Syria, explained her surprise about the earthquakes with the following words:

"I heard wrong at first that there was an earthquake in Türkiye. I heard it was 6.7 magnitude and my first thought was, 'Oh no, it's 6.7 magnitude and could be quite damaging to Türkiye' but then I looked online and saw that it was just an aftershock. I was devastated when I realized that the real earthquake was 7.8 magnitude."

Hubbard said that the earthquake that caused great destruction and loss of life in Türkiye and Syria was a tectonic earthquake, and that with the Arabian plate moving to the north, it also activated different underground layers in Türkiye.

"You might think this earthquake is unusual because a magnitude 7.8 scale is larger than any previously detected on this fault system," said Academician Hubbard.

 

 

*THE GROUND STILL REACTS TO THE FIRST BREAK*

Hubbard said that the last earthquake in Türikye was not very deep and that such earthquakes did more damage:

“Shallow earthquakes are worse. Because here people are closer to sliding and swinging. The earthquake itself lasted about 75 seconds. The shaking probably lasted much longer. Because the ground is still reacting to the first break." Hubbard continued his words, "The longer the shaking lasts, the more damage you will take."

The epicenter of the earthquake was located very close to the settlements. He stated that this creates an extremely destructive power. He said the following about the consecutive aftershocks:

“Aftershocks are a normal thing that happens after earthquakes and this is because all the faults in the area are suddenly re-stretched as the ground slides and so they respond to that stress by making their own little earthquakes, but here are more aftershocks as there are two big earthquakes breaking not one but two big faults and as a result doubles the amount of aftershocks.”

The US academic, who faced a devastating earthquake in Türkiye, explained that the region will not be safe from now on: 

"The time after the earthquake is the time when there is the highest probability of another earthquake. The regions around the fault are now under extra stress."

Besar Assad, visits, victims in Aleppo, hospital,

Biden talked about the earthquake in Türkiye: One of the worst in 100 years

Biden, Türkiye'deki depremi anlattı: 100 yılın en kötülerinden biri

 

*WE CAN'T EVEN PREDICT EARTHQUAKE*

Judith Hubbard, who has observed ground movements in various parts of the world from South Asia to the USA, explained that earthquakes are unpredictable with the following words:

"Earthquakes are inevitable. You can't stop them and we can't even predict them. But we can learn about them and find out how big they can be and what their impact will be. We can find out which places are at higher risk than others, and with tools like this we can become safer."

Stating that geoscientists see Turkey as a textbook when doing earthquake research, US academician Hubbard said:

"Because it is a truly fascinating tectonic environment. The Arabian plate collides in the north, in Eurasia, in the Himalayas, Iran or giant mountains in as we have seen in the Alps."

She made statements about the fact that there are more people in the world than before and there are settlements on fault lines, and this situation has devastating consequences. 

 

‘NO SUCH EARTHQUAKE OCCURRED IN THE EASTERN ANATOLIA’

Hubbard pointed out that earthquakes of this magnitude have occurred in Türkiye before. "However, no earthquake of this magnitude has occurred on the same fault and in the broken East Anatolian fault system," he spoke.

Reminding that earthquakes triggered each other on the North Anatolian fault line between the 1930s and 1960s, Hubbard stated that although it is not known clearly, this could happen in the south as well. He stated that during the researches, a slip of about 3 meters was detected in some parts of the fault:

“This (3 meters) is a normal value for a 7.8 earthquake. The largest ever recorded was 50 meters, but this happened underwater in Japan in 2011 and was not experienced by any human. In the 7.9 earthquake that took place in China, a measurement between 8 and 10 meters was made.”

The earthquake expert, on Twitter after the earthquake in Türkiye, said, "In an earthquake with a magnitude of 7.8, there may be an average of 5 meters of slippage. In other words, today's earthquake is based on a stretch spread over a period of about 300 years." had evaluated.

2023-02-10 16:25:51 | Son Güncelleme: 2023-02-10 17:04:07

 

TÜRKİYE'DEKİ BU DEPREMLER *OLAĞAN DIŞI*

ABD'li deprem uzmanı Türkiye'deki depremlerin 'olağan dışı' olduğunu belirterek: *Zemin hala tepki veriyor* Dedi...

ABD’li deprem uzmanı Doç. Dr. Judith Hubbard’dan çok çarpıcı bir değerlendirme geldi. Hubbard açıklamasında "Bu depremin olağan dışı olduğunu düşünebilirsiniz. 7,8'in ardından 7,5'lik depremin takip etmesi şaşırtıcıydı. Depremin kendisi yaklaşık 75 saniye sürdü. Sarsıntı muhtemelen çok daha uzun sürdü. Çünkü zemin hala ilk kırılmaya tepki veriyor" ifadelerini kullandı.

Türkiye son dakika gelen deprem haberlerini yakından takip ederken uzmanların açıklamaları da gelmeye devam ediyor. Son olarak Türkiye’de yaşanan deprem felaketini değerlendiren ABD’li uzmandan çarpıcı sözler geldi. ABD'li deprem uzmanı Doç. Dr. Judith Hubbard, Türkiye'de art arda yaşanan ve "asrın felaketi" olarak nitelenen Kahramanmaraş merkezli depremlerin, meydana geldiği fay sistemi üzerinde daha önce tespit edilenlerden daha büyük olması açısından "olağan dışı" olduğunu belirtti.

New York'taki Cornell Üniversitesi Jeoloji bölümünde deprem araştırmaları yapan Hubbard, "(ABD'deki ölçümlere göre) 7,8'in ardından 7,5'lik depremin takip etmesi şaşırtıcıydı. Bu, bir tür tetikleme olabilir. Çok yaygın görülen bir durum değil ve eminim ki çok daha zarar vericiydi." ifadelerini kullandı.

 

20 yıldır dünyanın çeşitli bölgelerindeki depremleri araştırdığını belirten Hubbard, Türkiye'nin güneyinde yaşanan depremlerin, "meydana gelen birçok depremden daha karmaşık" olduğunu söyleyerek "Pek çok farklı fay kopmuş gibi görünüyor ve sonra herkesin dikkatini çektiğini düşündüğüm şey, mutlak yıkım." dedi.

ABD'li akademisyen, "Binaların yıkılışının görüntüleri o kadar trajik ki... Ve bu, eski depremlere göre çok benzersiz kalıyor. Dolayısıyla yıkımın boyutu ile yıkımın görünürlüğünün birleşimi gerçekten ama gerçekten şoke edici." diye konuştu.

"BU DEPREMİN OLAĞAN DIŞI OLDUĞUNU DÜŞÜNEBİLİRSİNİZ"

Türkiye'de 10 ilde 13 milyondan fazla insanı etkileyen depremle ilgili duygularını ifade eden Judith Hubbard, bu konudaki şaşkınlığını ve üzüntüsünü şu sözlerle aktardı:

 

"Türkiye'de deprem olduğunu ilkin yanlış duymuşum. 6,7 büyüklüğünde olduğunu duydum ve ilk düşüncem, 'Oh, hayır, 6,7 büyüklüğünde ve Türkiye'ye oldukça zarar verici olabilir' şeklindeydi ama sonra internete baktığımda bunun sadece bir artçı sarsıntı olduğunu gördüm. Gerçek depremin 7,8 büyüklüğünde olduğunu anlayınca yıkıldım."

Hubbard, Türkiye ile Suriye'de de büyük yıkıma ve can kaybına sebep olan depremin tektonik bir deprem olduğunu, Arap levhasının kuzeye doğru hareket etmesiyle Türkiye'deki farklı yer altı tabakalarını da harekete geçirdiğini söyledi.

Akademisyen Hubbard, "Bu depremin olağan dışı olduğunu düşünebilirsiniz. Çünkü 7,8 ölçeğinde bir büyüklük, bu fay sistemi üzerinde daha önce tespit edilenlerin hepsinden daha büyüktür." tespitinde bulundu.

"SARSINTI NE KADAR UZUN SÜRERSE O KADAR FAZLA HASAR GÖRÜRSÜNÜZ"

Türkiye'deki son depremin çok derinde olmadığından dolayı, "sığ bir deprem" olarak adlandıran Doç. Dr. Hubbard, "Sığ depremler daha kötüdür. Çünkü burada insanlar kaymaya ve sallanmaya daha yakındır. Depremin kendisi yaklaşık 75 saniye sürdü. Sarsıntı muhtemelen çok daha uzun sürdü. Çünkü zemin hala ilk kırılmaya tepki veriyor." değerlendirmesini yaptı.

 

Böyle bir depremin çok daha zarar verici olduğunu ve hasarın boyutunu etkilediğini belirten Hubbard, "Sarsıntı ne kadar uzun sürerse o kadar fazla hasar görürsünüz." dedi.

Depremin merkez noktasının yerleşim yerinin (Pazarcık) hemen yanında olmasının, son derece yıkıcı etki oluşturduğunu belirten ABD'li akademisyen, meydana gelen yüzlerce artçı deprem hakkında şunları söyledi:

"Artçı sarsıntılar depremlerden sonra olan normal bir şeydir ve bunun nedeni zeminin kaymasıyla bölgedeki tüm fayların aniden yeni bir şekilde gerilmesidir. Ve böylece kendi küçük depremlerini yaparak bu strese yanıt verirler ama burada bir değil, iki büyük fayı kıran iki büyük deprem olduğu için daha fazla artçı şok olabilir. Ve sonuç olarak artçı şok miktarını iki katına çıkarır."

Judith Hubbard, Türkiye'de yıkıcı bir depremle yüzleşen bölgenin bundan sonra da güvende olduğunun söylenemeyeceğine vurgu yaparak "Depremden sonraki zaman, başka bir deprem olma ihtimalinin en yüksek olduğu zamandır. Fayın etrafındaki bölgeler artık ekstra stres altındadır ve bence Türkiye muhtemelen özellikle Kuzey Anadolu Fay Hattı'nın durumu nedeniyle bu riskin farkında." ifadelerini kullandı.

 

"DEPREMLER KAÇINILMAZDIR, ONLARI DURDURAMAZSINIZ"

Güney Asya'dan ABD'ye, dünyanın çeşitli bölgelerinde yer hareketlerini gözlemleyen Judith Hubbard, depremlerin öngörülemez olduğunu şu sözlerle açıkladı:

"Depremler kaçınılmazdır. Onları durduramazsınız ve biz onları tahmin bile edemeyiz. Ancak onlar hakkında bilgi edinebilir ve ne kadar büyük olabileceklerini ve etkilerinin ne olacağını öğrenebiliriz. Hangi yerlerin, diğerlerinden daha yüksek risk altında olduğunu öğrenebiliriz ve bu gibi araçlarla daha güvenli hale gelebiliriz."

Yer bilimcilerin, deprem araştırmaları yaparken Türkiye'yi bir ders kitabı gibi gördüklerini belirten ABD'li akademisyen Hubbard, "Çünkü gerçekten büyüleyici bir tektonik ortam. Arap levhası kuzeye, Avrasya'ya çarpıyor ve Türkiye'de, Himalaya'da, İran'da ya da Alpler'de gördüğümüz gibi dev dağlar inşa etmek yerine, ekstrüzyon tektoniği denen bir şey var; bu da bu iki fay sisteminin Kuzey Anadolu'da birbirlerine göre bir açı geliştirdiği anlamına geliyor. Türkiye'nin doğusu, batısı sıkışıp gidiyor." dedi.

Son olarak, depremlerdeki can ve mal kayıplarının artmasına ilişkin konuşan Hubbard, dünyada eskisinden daha fazla insan olduğu için, kıyı şeritleri ve fay hatları gibi tehlikeye açık bölgelerde yoğunlaşan toplulukların, doğal afet durumunda eskiye nazaran daha büyük zarar uğradığına, aksi takdirde dünyanın durumumun tektonik olarak eskisinden farklı olmadığına atıfta bulundu.

 

"DOĞU ANADOLU FAY SİSTEMİNDE BU BÜYÜKLÜKTE BİR DEPREM MEYDANA GELMEDİ"

Hubbard, 7,8'lik depremlerin sık sık görüldüğünü ve Türkiye'de de bu büyüklükte depremlerin daha önce olduğunu belirterek "Ancak aynı fay üzerinde ve kırılan Doğu Anadolu fay sisteminde bu büyüklükte bir deprem meydana gelmedi." diye konuştu.

Türkiye'de depreme maruz kalmamış binalar olduğunun altını çizen Hubbard, özellikle fayların sarsıldığı bir dönemde buna tepki olarak daha fazla deprem olma riskinin de bulunduğunu aktardı.

Hubbard, 1930 ile 1960'lı yıllar arasında Kuzey Anadolu fay hattında depremlerin birbirini tetiklediğini anımsatarak net olarak bilinemese de güneyde de bunun olabileceğini ifade etti.

Levhaların hareketiyle fay hatlarının etkilendiğine değinen Hubbard, bugüne kadar yapılan saha araştırmalarında fayın bazı kısımlarında 3 metre civarında bir kayma olduğunun tespit edildiğini dile getirdi.

Hubbard, normalde bulunan fay hattına göre depremlerin 2 ile 8 metre arasında bir kaymaya sebep olabileceğini kaydederek "Bu (3 metre), 7,8'lik bir deprem için normal bir değer. Şu ana kadar kaydedilen en büyük değer 50 metreydi ancak bu 2011'de Japonya'da su altında meydana gelmişti ve hiçbir insan tarafından tecrübe edilmemişti. 2008'de Çin'de gerçekleşen 7,9'luk depremde ise 8 ila 10 metre arasında bir ölçüm yapılmıştı." ifadelerini kullandı.

Japonya, Çin veya ABD'nin California eyaletindeki bina yapılarının Türkiye'ye uygun olmayabileceğini söyleyen Hubbard, "Binalar ve gelenekler farklı. Buna göre çalışmalı ve bu trajediyi anlayabilmeliyiz." dedi.

Deprem uzmanı akademisyen, Türkiye'deki depremin ardından Twitter'da, "7,8 büyüklüğünde bir depremde ortalama 5 metre kayma olabilir. Yani bugünkü deprem yaklaşık 300 yıllık sürece yayılmış bir gerilmeye dayanıyor." şeklinde değerlendirme yapmıştı.

11.02.2023 07:37 | Son Güncelleme: 11.02.2023 08:37

  

Earthquake Report: M 7.8 in Turkey/Syria

Posted on February 6, 2023

We just had a severe earthquake in south eastern Turkey, northwestern Syria.

https://earthquake.usgs.gov/earthquakes/eventpage/us6000jllz/executive 

This earthquake is the largest magnitude event in Turkey since 1939 and it looks like there will be many many casualties.

Hopefully international aid can rapidly travel there to assist in rescue and recovery. The videos I have seen so far are terrifying.

This is the same magnitude as the 1906 San Francisco earthquake.

There has already been an aftershock with a magnitude M 6.7. This size of an earthquake would be damaging on its own, let alone as it is an aftershock.

I will be updating this page over the next few days.

The East Anatolia fault is a left-lateral strike-slip fault system composed of many faults and is subdivided into different branches and different segments.

The first thing to remember is that people created these names and organized these faults using these names. The faults don’t know this and don’t care. It is possible that the people that organized these faults did not fully understand the reason these faults are here, so they may have organized them incorrectly. It may be centuries to millenia before we really know the real answer to why faults are where they are and how they relate to each other.

The Arabia plate moves north towards the Eurasia plate, forming the Alpide belt (perhaps the longest convergent plate boundary on Earth, extending from Australia/Indonesia in the east to offshore Portugal in the west. This convergence helps form the European Alps and the Asian Himalaya. In the aftershock poster below, we see the Bitlis-Zagros fold and thrust belt, also part of this convergence.

Turkey is escaping this convergence westwards. This escape has developed the right-lateral strike-slip North Anatolia fault system along the northern boundary of Turkey and the left-lateral East Anatolia fault system in southern Turkey.

During the 20th century, there was a series of large, deadly, and damaging earthquakes along the North Anatolia fault (NAF), culminating (for now) with the 1999 M7.6 Izmit Earthquake. The remaining segment of the NAF that has yet to rupture in this series is the section of the NAF that extends near Istanbul and into the Marmara Sea.

The East Anatolia fault (EAF) has a long history of large earthquakes and I include maps that show this history in the posters and in the report below (I have more to add later this week).

Today, I woke up to learn that there was a magnitude M 7.5 earthquake that happened since I posted this report the night before. This was not an aftershock but a newly triggered earthquake on a different fault than that that slipped during the M 7.8. However, there will be some people who will call this an aftershock.

https://earthquake.usgs.gov/earthquakes/eventpage/us6000jlqa/executive

The aftershocks have been filling in to reveal what faults are involved and there are many faults involved in this sequence. I include a larger scale view of these faults in the updated aftershock interpretive poster below. >>>

This M 7.5 earthquake is on a different fault than the main part of the sequence (the Çardak fault). The main sequence appears to be on two segments of the main branch of the East Anatolia fault

Below is my interpretive poster for this earthquake

I plot the seismicity from the past month, with diameter representing magnitude (see legend). I include earthquake epicenters from 1922-2022 with magnitudes M ≥ 3.0 in one version.

I plot the USGS fault plane solutions (moment tensors in blue and focal mechanisms in orange), possibly in addition to some relevant historic earthquakes.

A review of the basic base map variations and data that I use for the interpretive posters can be found on the Earthquake Reports page. I have improved these posters over time and some of this background information applies to the older posters.

Some basic fundamentals of earthquake geology and plate tectonics can be found on the Earthquake Plate Tectonic Fundamentals page. 

I INCLUDE SOME INSET FIGURES. SOME OF THE SAME FIGURES ARE LOCATED IN DIFFERENT PLACES ON THE LARGER SCALE MAP BELOW.

In the upper right corner is a map from Armijo et al. (1999) that shows the plate boundary faults and tectonic plates in the region. This M 6.7 earthquake, denoted by the blue star, is along the East Anatolia fault, a left-lateral strike-slip plate boundary fault.

In the upper left corner is a comparison of the shaking intensity modeled by the USGS and the shaking intensity based on peoples’ “boots on the ground” observations. People felt intensities exceeding MMI 7.

To the right of the intensity map is a figure from Duman and Emre (2013). This shows the historic earthquakes along the EAF.

In the lower right corner is a map that shows the faults in the region. Note how the topography reflects the tectonics.

In the lower center lerft is a plot that shows how the shaking intensity models and reports relate to each other. The horizontal axis is distance from the earthquake and the vertical axis is shaking intensity (using the MMI scale, just like in the map to the right: these are the same datasets).

Here is the map with a month’s seismicity plotted. 

Here is the map with a day’s seismicity plotted (prepared a few hours after the main shock).

There are some additional inset figures here:

The USGS Finite Fault Model (FFM) is shown on center right. This graphic shows how much the USGS model suggests that the fault slipped during this earthquake.

To the right of the legend are two maps that show (left) liquefaction susceptibility and (right) landslide probability. These are based on empirical models from the USGS that show the chance an area may have experienced these processes that may have happened as a result of the ground shaking from the earthquake. I spend more time explaining these types of models and what they represent in this Earthquake Report for the recent event in Albania.

I include a plot of the tide gage data from Erdemli.

UPDATE: 6 February 2023

Here is the map with about a day’s seismicity plotted.

I plot the 2023 earthquakes in blue and the 2020 earthquakes in green.

UPDATE: 8 February 2023

Here is the same two maps with about 3 day’s seismicity plotted. There are other modest changes.

 

Some Relevant Discussion and Figures

This is the plate tectonic map from Armijo et al., 1999.

Tectonic setting of continental extrusion in eastern Mediterranean. Anatolia-Aegean block escapes westward from Arabia-Eurasia collision zone, toward Hellenic subduction zone. Current motion relative to Eurasia (GPS [Global Positioning System] and SLR [Satellite Laser Ranging] velocity vectors, in mm/yr, from Reilinger et al., 1997). In Aegean, two deformation regimes are superimposed (Armijo et al., 1996): widespread, slow extension starting earlier (orange stripes, white diverging arrows), and more localized, fast transtension associated with later, westward propagation of North Anatolian fault (NAF). EAF—East Anatolian fault, K—Karliova triple junction, DSF—Dead Sea fault, NAT—North Aegean Trough, CR—Corinth Rift.Box outlines Marmara pull-apart region, where North Anatolian fault enters Aegean.

Here is the tectonic map from Dilek and Sandvol (2009).

Tectonic map of the Aegean and eastern Mediterranean region showing the main plate boundaries, major suture zones, fault systems and tectonic units. Thick, white arrows depict the direction and magnitude (mm a21) of plate convergence; grey arrows mark the direction of extension (Miocene–Recent). Orange and purple delineate Eurasian and African plate affinities, respectively. Key to lettering: BF, Burdur fault; CACC, Central Anatolian Crystalline Complex; DKF, Datc¸a–Kale fault (part of the SW Anatolian Shear Zone); EAFZ, East Anatolian fault zone; EF, Ecemis fault; EKP, Erzurum–Kars Plateau; IASZ, Izmir–Ankara suture zone; IPS, Intra–Pontide suture zone; ITS, Inner–Tauride suture; KF, Kefalonia fault; KOTJ, Karliova triple junction; MM, Menderes massif; MS, Marmara Sea; MTR, Maras triple junction; NAFZ, North Anatolian fault zone; OF, Ovacik fault; PSF, Pampak–Sevan fault; TF, Tutak fault; TGF, Tuzgo¨lu¨ fault; TIP, Turkish–Iranian plateau (modified from Dilek 2006).

This is the Woudloper (2009) tectonic map of the Mediterranean Sea. The yellow/orange band represents the Alpide Belt, a convergent plate boundary that extends from western Europe, through the Middle East, beneath northern India and Nepal (forming the Himalayas), through Indonesia, terminating east of Australia.

Below is a series of figures from Jolivet et al. (2013). These show various data sets and analyses for Greece and Turkey.

Upper Panel (A): This is a tectonic map showing the major faults and geologic terranes in the region. The fault possibly associated with today’s earthquake is labeled “Neo Tethys Suture” on the map, for the Eastern Anatolia fault.

Lower Panel (B): This shows historic seismicity for the region. Note the general correlation with the faults in the upper panel.

A: Tectonic map of the Aegean and Anatolian region showing the main active structures
(black lines), the main sutures zones (thick violet or blue lines), the main thrusts in the Hellenides where they have not been reworked by later extension (thin blue lines), the North Cycladic Detachment (NCDS, in red) and its extension in the Simav Detachment (SD), the main metamorphic units and their contacts; AlW: Almyropotamos window; BD: Bey Daglari; CB: Cycladic Basement; CBBT: Cycladic Basement basal thrust; CBS: Cycladic Blueschists; CHSZ: Central Hellenic Shear Zone; CR: Corinth Rift; CRMC: Central Rhodope Metamorphic Complex; GT: Gavrovo–Tripolitza Nappe; KD: Kazdag dome; KeD: Kerdylion Detachment; KKD: Kesebir–Kardamos dome; KT: Kephalonia Transform Fault; LN: Lycian Nappes; LNBT: Lycian Nappes Basal Thrust; MCC: Metamorphic Core Complex; MG: Menderes Grabens; NAT: North Aegean Trough; NCDS: North Cycladic Detachment System; NSZ: Nestos Shear Zone; OlW: Olympos Window; OsW: Ossa Window; OSZ: Ören Shear Zone; Pel.: Peloponnese; ÖU: Ören Unit; PQN: Phyllite–Quartzite Nappe; SiD: Simav Detachment; SRCC: South Rhodope Core Complex; StD: Strymon Detachment; WCDS: West Cycladic Detachment System; ZD: Zaroukla Detachment. B: Seismicity. Earthquakes are taken from the USGS-NEIC database. Colour of symbols gives the depth (blue for shallow depths) and size gives the magnitude (from 4.5 to 7.6).

Upper Panel (C): These red arrows are Global Positioning System (GPS) velocity vectors. The velocity scale vector is in the lower left corner. The main geodetic (study of plate motions and deformation of the earth) signal here is the westward motion of the North Anatolian fault system as it rotates southward as it traverses Greece. The motion trends almost south near the island of Crete, which is perpendicular to the subduction zone.

Lower Panel (D): This map shows the region of mid-Cenozoic (Oligo-Miocene) extension (shaded orange). It just happens that there is still extension going on in parts of this prehistoric extension. 

 

C: GPS velocity field with a fixed Eurasia after Reilinger et al. (2010) D: the domain affected by distributed post-orogenic extension in the Oligocene and the Miocene and the stretching lineations in the exhumed metamorphic complexes.

Upper Panel (E): This map shows where the downgoing slab may be located (in blue), along with the volcanic centers associated with the subduction zone in the past.

Lower Panel (F): This map shows the orientation of how seismic waves orient themselves differently in different places (anisotropy). We think seismic waves travel in ways that reflects how tectonic strain is stored in the earth. The blue lines show the direction of extension in the asthenosphere, green lines in the lithospheric mantle, and red lines for the crust.

E: The thick blue lines illustrate the schematized position of the slab at ~150 km according to the tomographic model of Piromallo and Morelli (2003), and show the disruption of the slab at three positions and possible ages of these tears discussed in the text. Velocity anomalies are displayed in percentages with respect to the reference model sp6 (Morelli and Dziewonski, 1993). Coloured symbols represent the volcanic centres between 0 and 3 Ma after Pe-Piper and Piper (2006). F: Seismic anisotropy obtained from SKS waves (blue bars, Paul et al., 2010) and Rayleigh waves (green and orange bars, Endrun et al., 2011). See also Sandvol et al. (2003). Blue lines show the direction of stretching in the asthenosphere, green bars represent the stretching in the lithospheric mantle and orange bars in the lower crust.

Upper Panel (G): This is the map showing focal mechanisms in the poster above. Note the strike slip earthquakes associated with the North Anatolia and East Anatolia faults and the thrust/reverse mechanisms associated with the thrust faults.

G: Focal mechanisms of earthquakes over the Aegean Anatolian region.

Here is a map showing tectonic domains (Taymaz et al., 2007).

 

Schematic map of the principal tectonic settings in the Eastern Mediterranean. Hatching shows areas of coherent motion and zones of distributed deformation. Large arrows designate generalized regional motion (in mm a21) and errors (recompiled after McClusky et al. (2000, 2003). NAF, North Anatolian Fault; EAF, East Anatolian Fault; DSF, Dead Sea Fault; NEAF, North East Anatolian Fault; EPF, Ezinepazarı Fault; CTF, Cephalonia Transform Fault; PTF, Paphos Transform Fault.

Here is a tectonic overview figure from Duman and Emre, 2013.

 

The main fault systems of the AN–AR and TR–AF plate boundaries (modified from Sengor & Yılmaz 1981; Saroglu et al. 1992a, b; Westaway 2003; Emre et al. 2011a, b, c). Arrows indicate relative plate motions (McClusky et al. 2000). Abbreviations: AN, Anatolian microplate; AF, African plate; AR, Arabian plate; EU, Eurasian plate; NAFZ, North Anatolian Fault Zone; EAFZ, East Anatolian Fault Zone; DSFZ, Dead Sea Fault Zone; MF; Malatya Fault, TF, Tuzgo¨lu¨ fault; EF, Ecemis¸ fault; SATZ, Southeast Anatolian Thrust Zone; SS, southern strand of the EAFZ; NS, northern strand of the EAFZ.

This is a map that shows the subdivisions of the EAF (Duman and Emre, 2013). Note Lake Hazar for reference.

Map of the East Anatolian strike-slip fault system showing strands, segments and fault jogs. Abbreviations: FS, fault Segment; RB, releasing bend; RS, releasing stepover; RDB, restraining double bend; RSB, restraining bend; PB, paired bend; (1) Du¨zic¸i–Osmaniye fault segment; (2) Erzin fault segment; (3) Payas fault segment; (4) Yakapınar fault segment; (5) C¸ okak fault segment; (6) Islahiye releasing bend; (7) Demrek restraining stepover; (8) Engizek fault zone; (9) Maras¸ fault zone.

This map shows the fault mapping from Duman and Emre, 2013. Note Lake Hazar for reference. We can see some of the thrust faults mapped as part of the Southeast Anatolia fault zone.

Map of the (a) Palu and (b) Puturge segments of the East Anatolian fault. Abbreviations: LHRB, Lake Hazar releasing bend; PS, Palu segment; ES, Erkenek segment; H, hill; M, mountain; C, creek; (1) left lateral strike-slip fault; (2) normal fault; (3) reverse or thrust fault; (4) East Anatolian Fault; (5) Southeastern Anatolian Thrust Zone; (6) syncline;(7) anticline; (8) undifferentiated Holocene deposits; (9) undifferentiated Quaternary deposits; (10) landslide.

This is the figure from Duman and Emre (2013) that shows the spatial extent for historic earthquakes on the EAF.

Surface ruptures produced by large earthquakes during the 19th and 20th centuries along the EAF. Data from Arpat (1971), Arpat and S¸arog˘lu (1972), Seymen and Aydın (1972), Ambraseys (1988), Ambraseys and Jackson (1998), Cetin et al. (2003), Herece (2008), Karabacak et al. (2011) and this study. Ruptured fault segments are highlighted.

Shaking Intensity

Here is a figure that shows a more detailed comparison between the modeled intensity and the reported intensity. Both data use the same color scale, the Modified Mercalli Intensity Scale (MMI). More about this can be found here. The colors and contours on the map are results from the USGS modeled intensity. The DYFI data are plotted as colored dots (color = MMI, diameter = number of reports). In addition to what I write below, the data on the left are from the M 7.5 and the data on the right are from the M 7.8.

In the upper panel is the USGS Did You Feel It reports map, showing reports as colored dots using the MMI color scale. Underlain on this map are colored areas showing the USGS modeled estimate for shaking intensity (MMI scale).

In the lower panel is a plot showing MMI intensity (vertical axis) relative to distance from the earthquake (horizontal axis). The models are represented by the green and orange lines. The DYFI data are plotted as light blue dots. The mean and median (different types of “average”) are plotted as orange and purple dots. Note how well the reports fit the green line, the orange line, or neither line. What reasons can you think that may be explain these real observation deviations from the models.

Below the lower plot is the USGS MMI Intensity scale, which lists the level of damage for each level of intensity, along with approximate measures of how strongly the ground shakes at these intensities, showing levels in acceleration (Peak Ground Acceleration, PGA) and velocity (Peak Ground Velocity, PGV).

 

Earthquake Triggered Landslides

There are many different ways in which a landslide can be triggered. The first order relations behind slope failure (landslides) is that the “resisting” forces that are preventing slope failure (e.g. the strength of the bedrock or soil) are overcome by the “driving” forces that are pushing this land downwards (e.g. gravity). The ratio of resisting forces to driving forces is called the Factor of Safety (FOS). We can write this ratio like this:

FOS = Resisting Force / Driving Force

When FOS > 1, the slope is stable and when FOS < 1, the slope fails and we get a landslide. The illustration below shows these relations. Note how the slope angle α can take part in this ratio (the steeper the slope, the greater impact of the mass of the slope can contribute to driving forces). The real world is more complicated than the simplified illustration below.

Landslide ground shaking can change the Factor of Safety in several ways that might increase the driving force or decrease the resisting force. Keefer (1984) studied a global data set of earthquake triggered landslides and found that larger earthquakes trigger larger and more numerous landslides across a larger area than do smaller earthquakes. Earthquakes can cause landslides because the seismic waves can cause the driving force to increase (the earthquake motions can “push” the land downwards), leading to a landslide. In addition, ground shaking can change the strength of these earth materials (a form of resisting force) with a process called liquefaction.

Sediment or soil strength is based upon the ability for sediment particles to push against each other without moving. This is a combination of friction and the forces exerted between these particles. This is loosely what we call the “angle of internal friction.” Liquefaction is a process by which pore pressure increases cause water to push out against the sediment particles so that they are no longer touching.

An analogy that some may be familiar with relates to a visit to the beach. When one is walking on the wet sand near the shoreline, the sand may hold the weight of our body generally pretty well. However, if we stop and vibrate our feet back and forth, this causes pore pressure to increase and we sink into the sand as the sand liquefies. Or, at least our feet sink into the sand.

Below is a diagram showing how an increase in pore pressure can push against the sediment particles so that they are not touching any more. This allows the particles to move around and this is why our feet sink in the sand in the analogy above. This is also what changes the strength of earth materials such that a landslide can be triggered.

Below is a diagram based upon a publication designed to educate the public about landslides and the processes that trigger them (USGS, 2004). Additional background information about landslide types can be found in Highland et al. (2008). There was a variety of landslide types that can be observed surrounding the earthquake region. So, this illustration can help people when they observing the landscape response to the earthquake whether they are using aerial imagery, photos in newspaper or website articles, or videos on social media. Will you be able to locate a landslide scarp or the toe of a landslide? This figure shows a rotational landslide, one where the land rotates along a curvilinear failure surface.

Here is an excellent educational video from IRIS and a variety of organizations. The video helps us learn about how earthquake intensity gets smaller with distance from an earthquake. The concept of liquefaction is reviewed and we learn how different types of bedrock and underlying earth materials can affect the severity of ground shaking in a given location. The intensity map above is based on a model that relates intensity with distance to the earthquake, but does not incorporate changes in material properties as the video below mentions is an important factor that can increase intensity in places.

If we look at the map at the top of this report, we might imagine that because the areas close to the fault shake more strongly, there may be more landslides in those areas. This is probably true at first order, but the variation in material properties and water content also control where landslides might occur.

There are landslide slope stability and liquefaction susceptibility models based on empirical data from past earthquakes. The USGS has recently incorporated these types of analyses into their earthquake event pages. More about these USGS models can be found on this page.

Below is a figure that shows both landslide probability and liquefaction susceptibility maps for this M 7.8 earthquake.

Fault Scaling Relations

There is a seminal paper (Wells and Coppersmith, 1994) where these geologists compiled the existing data from global earthquakes.

They extracted different aspects of the physical size of these earthquakes so that they could develop relations between the earthquake size (e.g., length of the fault that ruptured the surface of the Earth) and earthquake magnitude. Since these relations are based on real data from real earthquakes, we call these empirical scaling relations (i.e., the size of the earthquake slip “scales” with the size of the magnitude).

Their analyses also subdivided the earthquakes in ways to see if different types of earthquakes (strike-slip, normal, or thrust/reverse) had different scaling relations.

Some have updated the database of earthquake observations. However, these updated scaling relations are not that much different than the original Wells and Coppersmith (1994) scaling relations. Perhaps there is sufficient variation in earthquake size that we have yet to deconvolve all the variation in fault ruptures?

Below I present the Wells and Coppersmith (1994) scaling relations for subsurface earthquake slip length. I do this because it may be a while until we have a good estimate for other measures (like surface rupture length) but we can estimate the subsurface fault length in different ways with existing data (like the spatial extent of aftershocks).

In the upper panel I list the rough length of three fault segments that are part of the East Anatolia fault system.

I use the relations represented by the diagonal lines in the center panel to calculate the earthquake magnitude for faults of varying length (100-200km). Based on their relations, a magnitude M 7.8 earthquake may have ruptured a fault with a subsurface length of 200 km.

Seismic Hazard and Seismic Risk

These are the two seismic maps from the Global Earthquake Model (GEM) project, the GEM Seismic Hazard and the GEM Seismic Risk maps from Pagani et al. (2018) and Silva et al. (2018).

 

The Global Earthquake Model (GEM) Global Seismic Hazard Map (version 2018.1) depicts the geographic distribution of the Peak Ground Acceleration (PGA) with a 10% probability of being exceeded in 50 years, computed for reference rock conditions (shear wave velocity, VS30, of 760-800 m/s). The map was created by collating maps computed using national and regional probabilistic seismic hazard models developed by various institutions and projects, and by GEM Foundation scientists. The OpenQuake engine, an open-source seismic hazard and risk calculation software developed principally by the GEM Foundation, was used to calculate the hazard values. A smoothing methodology was applied to homogenise hazard values along the model borders. The map is based on a database of hazard models described using the OpenQuake engine data format (NRML). Due to possible model limitations, regions portrayed with low hazard may still experience potentially damaging earthquakes.

Here is a view of the GEM seismic hazard map for Europe.

Here is a map that displays an estimate of seismic hazard for the region (Jenkins et al., 2010). This comes from Giardini et al. (1999).

The Global Seismic Hazard Map. Peak ground acceleration (pga) with a 10% chance of exceedance in 50 years is depicted in m/s2. The site classification is rock everywhere except Canada and the United States, which assume rock/firm soil site classifications. White and green correspond to low seismicity hazard (0%-8%g), yellow and orange correspond to moderate seismic hazard (8%-24%g), pink and dark pink correspond to high seismicity hazard (24%-40%g), and red and brown correspond to very high seismic hazard (greater than 40%g).

The Global Seismic Risk Map (v2018.1) presents the geographic distribution of average annual loss (USD) normalised by the average construction costs of the respective country (USD/m²) due to ground shaking in the residential, commercial and industrial building stock, considering contents, structural and non-structural components. The normalised metric allows a direct comparison of the risk between countries with widely different construction costs. It does not consider the effects of tsunamis, liquefaction, landslides, and fires following earthquakes. The loss estimates are from direct physical damage to buildings due to shaking, and thus damage to infrastructure or indirect losses due to business interruption are not included. The average annual losses are presented on a hexagonal grid, with a spacing of 0.30 x 0.34 decimal degrees (approximately 1,000 km² at the equator). The average annual losses were computed using the event-based calculator of the OpenQuake engine, an open-source software for seismic hazard and risk analysis developed by the GEM Foundation. The seismic hazard, exposure and vulnerability models employed in these calculations were provided by national institutions, or developed within the scope of regional programs or bilateral collaborations.

Here is a view of the GEM seismic risk map for Europe.

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