Update on the Black Sea earthquakes

Since my post this morning about the three earthquakes in the Ukraine side of the Black Sea, one more happened today at 16:10:56 (UTC).

Here is the map with all four events:

I also found a tectonic map with the major fault zones at the end Jurassic (after Robinson et al, 1997), that may shed some light regarding the seismicity in the Black Sea.  It appears that the lone event is related to a fault zone bounding the Shatsky Ridge in the eastern Black Sea, and the three clustered ones SW of Sevastopol are near the Jurassic tectonic boundary of the Tavrik-Kure basin.

Low magnitude earthquakes are not uncommon in the Black Sea.  Below is a list of all the 2010 seismic events with a magnitude greater than 2 on the Richter scale (from the National Institute of Earth Physics, Romania):

Black Sea Earthquakes

On Saturday, three earthquakes in the Black Sea succeeded over an interval of five minutes.

The first was located west of Sevastopol and occurred at 18:51 (UTC).

The second took place SE of Sevastopol at 18:55:24 (UTC).

The third earthquake was located very close to the first, about 64km W of Sevastopol, and occurred at 18:55:52 (UTC).  The four maps above are courtesy of the National Institute for Earth Physics in Romania.

I do not know much about the earthquakes in the Black Sea, since the big events in Romania are related to the Vrancea region (see my previous post here on the geology and wine - seismic terroir).  I will try to find out more about the focal mechanism and other information, but if any of you know more, please leave comments.  

From information I found on EarthquakeDB, in 103 A.D an earthquake in Ukraine (map below) associated with a Tsunami had the epicenter located very close to the ones that occurred yesterday.  Fortunately, no Tsunami on Saturday!

Geology and wine #4 - Wine and Earthquakes

Some of the oldest wine growing regions in Romania are in Vrancea, an area also known for the highest seismicity in Romania.  The red ellipse on the image below shows where Vrancea is located: within a structurally complex area named in Romanian "zona de curbura" literally translated as the "bend zone", because the Carpathian arch bends as it transitions from the Eastern Carpathians to the Southern Carpathians.

I'll start with the earthquakes, so that my post will have a happy ending, on the topic of wine.
Vrancea is a subduction zone and the widely accepted model for the seismicity is shown in the E-W cross section below (sourced from the Romanian earthquake forum, Cutremur.net):

It is postulated that a slab from the plunging plate detached about 10 million years ago and its motion, as it sinks and is consumed in the mantle, generates quakes. The depth range for the hypocenters varies between 15 and 220 km.  Areas to the NE or SW of Vrancea are the most affected during an earthquake, which is why Bucharest is the number two European capital with the highest seismicity (after Lisbon).  I went through a 7.4 earthquake in Bucharest in 1977, and it was not fun (I wasn't even a geologist yet at the time, to at least find "pleasure" in the scientific aspect of the event).  More on Vrancea quakes here and here.

As for the wine, the best known wine regions in Vrancea are Panciu, Odobesti and Cotesti.  The best wines from native grapes here are the Feteasca Regala, Tamaiosa Romaneasca and Feteasca Neagra.  The last is my favorite, with its bouquet of blackberries and dried plums, and a hint of bitterness as it gets more mature.