Mag 5.5 Earthquake, Romania and Earthquakes in Ionian Sea

[Astronuc]

I noticed a relatively strong earthquake in SE Europe this weekend.
https://earthquake.usgs.gov/earthquakes/eventpage/us1000hi43/executive
M5.5 - 16km SE of Comandau, Romania
2018-10-28 00:38:11 (UTC)
45.652°N 26.403°E
151.0 km depth - very deep

Then I noticed several earthquakes in the Ionian Sea off the east coast of Greece. Most were between 4 to 5 Mag, but one today was 5.6 Mag.

https://earthquake.usgs.gov/earthquakes/eventpage/us1000hivt/executive
M 5.6 - 40km SW of Mouzaki, Greece
2018-10-30 02:59:58 (UTC)
37.531°N 20.440°E
10.0 km depth

There are moderate earthquakes in Turkey, in the Mediterranean Sea of Cyprus, in Georgia and in Iran.

Wondering if this will lead to a strong earthquake in the region.

 

[davenn]

Wondering if this will lead to a strong earthquake in the region.

well there was the M 6.8 event offshore SW Greece last week

that 5.6 you listed above was an aftershock to it

Dave

 

[Astronuc]

well there was the M 6.8 event offshore SW Greece last week

that 5.6 you listed above was an aftershock to it

Dave

Thanks, Dave. I should have checked. I managed to miss it.

https://earthquake.usgs.gov/earthquakes/eventpage/us1000hhb1/executive
M 6.8 - 33km SW of Mouzaki, Greece
2018-10-25 22:54:51 (UTC)
37.506°N 20.563°E
14.0 km depth - shallow

Some history and insight
https://earthquake.usgs.gov/earthquakes/eventpage/us1000hhb1/region-info

 

[Rive]

Regarding that 6.8 in Greece: is this 'normal' to have this many aftershocks, at this range? There was ~ 60 events between 4.2 and 5.6 since the main one, but actually nothing below 4 (according to earthquake.usgs.gov).

 

[Astronuc]

Regarding that 6.8 in Greece: is this 'normal' to have this many aftershocks, at this range? There was ~ 60 events between 4.2 and 5.6 since the main one, but actually nothing below 4 (according to earthquake.usgs.gov).

The USGS does not necessarily report on lower than Mag 4.5 around the world, or below Mag 2.5 in the US. One has to look at the filters or limitations on the data.
https://earthquake.usgs.gov/data/comcat/data-availability.php

One can get more information from https://earthquake.usgs.gov/earthquakes/eventpage/us1000hhb1/executive , and select View Nearby Seismicity

For more details, see http://www.geophysics.geol.uoa.gr/stations/maps/recent.html, a website by the Seismological Laboratory, University of Athens, Greece.
Select at least 10 days (from day of this post) to capture the recent Mag 6.8 on October 25. Notice activity before and after the Mag 6.8 earthquake.

26/10 03:54:54, M: 3.5
26/10 02:36:08, M: 3.9
26/10 02:17:33, M: 4.0
26/10 02:09:32, M: 3.9
26/10 01:46:00, M: 3.6
26/10 01:43:30, M: 3.5
26/10 01:10:45, M: 3.5
26/10 01:05:58, M: 4.5
26/10 00:32:54, M: 4.6
26/10 00:31:41, M: 3.6
26/10 00:23:14, M: 4.4
26/10 00:13:40, M: 4.5
26/10 00:06:27, M: 3.7
25/10 23:37:24, M: 3.9
25/10 23:09:21, M: 5.1
25/10 22:54:50, M: 6.8
25/10 22:52:59, M: 2.7
25/10 22:22:54, M: 4.8
25/10 21:13:30, M: 0.8
25/10 20:12:51, M: 1.8
25/10 18:30:24, M: 1.9
25/10 14:45:35, M: 1.1
25/10 14:38:14, M: 1.3
25/10 11:59:27, M: 1.4
25/10 11:01:19, M: 2.1
25/10 08:15:59, M: 1.3
25/10 08:09:34, M: 2.7
25/10 02:47:40, M: 1.8
25/10 02:10:34, M: 1.9
25/10 01:57:40, M: 1.1
25/10 01:52:28, M: 2.1
25/10 01:43:49, M: 1.0
25/10 01:08:14, M: 1.3

In the case of the US, see https://pnsn.org/ for the Pacific Northwest Seismic Network, and compare their map to the USGS Map for Latest Earthquakes over the same time period, and in the northeast US see http://aqms.ldeo.columbia.edu/recent.html

In the US, there is the Advanced National Seismic System (ANSS)
https://earthquake.usgs.gov/monitoring/anss/

World wide is Global Seismographic Network (GSN)
https://earthquake.usgs.gov/monitoring/gsn/

 

[Rive]

Thanks for the links. The presence of the smaller ones makes it less weird, but still, is it normal to have this mucs aftershocks (with that many 4+ ones)?

 

[davenn]

but still, is it normal to have this mucs aftershocks (with that many 4+ ones)?

yup, definitely normal ... A M6.8 is a significant event and it was shallow so there is going to be lots of aftershocks as stresses
in the fault(s) and surrounding area readjust

 

[davenn]

There was ~ 60 events between 4.2 and 5.6 since the main one, but actually nothing below 4 (according to earthquake.usgs.gov).

USGS data doesn't show events below M4.0 ( usually M4.5) outside of the USA

 

[Rive]

yup, definitely normal ...

Thanks! So nothing like a new vulcano there, or anything? ......By the way, how would that 'sound' like?

 

[davenn]

So nothing like a new vulcano there,

Not likely ... this region is seismically active and the USGS states in its info that there has been 13 events around this magnitude in the surrounding region
of SW Greece and offshore.

Generally the Mediterranean area is a subduction zone with the African Plate going down under the European end of the Eurasian Plate.
This is what causes the well known volcanic activity in the region ... Mt Vesuvius, Thera Caldera ( Santorini Islands), Stromboli, Mt Etna,
to name a few.

...By the way, how would that 'sound' like?

what sound ? the earthquake ?
I have experienced a number of quakes above M6.0 back when I used to live in southern New Zealand. Sometimes there's a
rumbling - roaring sound even before the shaking starts. Other times the sound is during the shaking.
This is noise from the ground, not the creaking of the building etc.Dave

 

[Rive]

Sorry for the confusion: I meant, if there is a specific pattern in the amount/frequency/strength/depth of earthquakes if the reason is a new vulcano.

 

[Nik_2213]

Are you thinking of the infamous 'harmonic tremor' as magma rises in chimney ??
Be Not There !

FWIW, a friend passed on an interesting observation about geology students: Budding volcanologists and seismologists *always* park facing the exit...

 

[Rive]

'harmonic tremor'

That just gave me the right direction for a search, thanks!

FWIW, a friend passed on an interesting observation about geology students: Budding volcanologists and seismologists *always* park facing the exit...

I was told once that the ratio of hypochonders in the first years any medical university will be ~ 110%: for the few who is not worrying about their health there are always more with self-suspected multiple personalities...

 

[davenn]

Sorry for the confusion: I meant, if there is a specific pattern in the amount/frequency/strength/depth of earthquakes if the reason is a new vulcano.

'harmonic tremor'

Volcanic harmonic tremor produces quite a unique record on a seismogram as there is no identifiable P, S or surface waves.
Rather there is just a continuous vibration with not a lot of variation in amplitude that can last minutes or hours ...

An example ...

http://earthquake-report.com/wp-content/uploads/2012/07/RETU_SHZ_EC_-.2012072900.gifDave