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Dr. Judith Hubbard Profile picture
Dr. Judith Hubbard
@JudithGeology
Plate tectonics to earthquakes & everything in between • Vstng Asst Prof @CornellEAS • Prev @EOS_SG, Caltech, Harvard • Mom/3 • Read my earthquake newsletter:
Oct 17, 2023 • 5 tweets • 2 min read
BSSA just published a paper where the authors claim to predict earthquakes days in advance, using AI. A quick read-through raises many question.

Does anybody know about this study and why BSSA is publishing AI/earthquake prediction papers now?

1/
doi.org/10.1785/012023… Although the paper is framed around "earthquake forecasting," it's a prediction paper. They use the word prediction in both the paper and the supplement.

2/
Mar 29, 2023 • 9 tweets • 3 min read
Today's M4.7 earthquake in Italy likely occurred on an east-west strike-slip fault that previously produced a pair of ~M5.8 earthquakes in 2002.

The 2002 earthquakes were horrible; fortunately today's event was much smaller.

1/
earthquake.usgs.gov/earthquakes/ev… The 2002 Molise earthquakes occurred within ~1 day of each other (Oct 31 and Nov 1). The first quake collapsed a school, killing half the children inside (26 of 51). At the time, the area was considered to have no seismic hazard.

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en.wikipedia.org/wiki/2002_Moli…
Mar 28, 2023 • 14 tweets • 4 min read
Several people have asked me recently about whether we should expect a large earthquake on the Afrin fault, south of the Feb 6 rupture.

First: no one can predict earthquakes, so if anyone has told you they can, they are wrong.

But let's take a look anyway.

1/ First, what is the Afrin fault? The AFEAD dataset has a small fault listed under this name, running through the city of Kilis, Turkey. An extension of this fault is mapped near the city of Afrin, Syria.

These faults are part of the northern end of the Dead Sea Fault.

2/
Mar 28, 2023 • 8 tweets • 4 min read
Why did a M5 earthquake occur HERE yesterday, in what is apparently the middle of the African Plate?

Answer: It's not the middle of the African Plate, it's the East African Rift: the continent is pulling apart at a rate of ~1-5 mm/yr.

1/ Yesterday's earthquake was just the latest in a long series of earthquakes - and not the largest, either; there was a M6 in 2020 to the south.

The "rift" isn't a single fault, but many.

2/
Mar 28, 2023 • 17 tweets • 6 min read
A M6 earthquake occurred a few hours ago offshore Japan. Due to its magnitude & distance from shore, it was not damaging, but the setting is interesting to explore.

1/ This is a subduction zone: the Pacific Plate is subducting below the Okhotsk Plate at a rate of ~9 cm/yr. The Okhotsk Plate used to be considered part of the North American Plate (even though it's in Japan!) but it actually moves slightly differently.

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en.wikipedia.org/wiki/Okhotsk_P…
Mar 27, 2023 • 12 tweets • 3 min read
A lot of earthquakes have one large event followed by aftershocks.

But sometimes, we see something like this instead: a set of several similar-magnitude events (with additional small seismicity).

That's what has been happening near Kayseri, Turkey.

1/ It started on Feb. 23, with a M3.8. Then, a few days later, a little microseismicity.

Then, suddenly, a M4.6 on Feb. 28.

(EMSC reports it as an mb4.4, which here is converted to Mw4.6 - different ways of measuring magnitude.)

2/
Mar 26, 2023 • 7 tweets • 2 min read
It's been 9 days since this M4.7 earthquake occurred near Bolu, Turkey - let's take a look at aftershocks in the area.

Aftershocks are expected after an earthquake; we tend to see them decrease at a rate of 1/time. (x aftershocks on day 1, x/N on day N.)

1/ This plot has 4 parts:

A map, showing seismicity since Sep 2022, colored by time

The projection of seismicity to the right, plotted with time on the x-axis

A time series below, showing when the seismicity on the map occurred

A histogram, showing number of events/day

2/ Image
Mar 22, 2023 • 4 tweets • 2 min read
A M4.6 earthquake isn't that exciting, even in California.

But what IS exciting is that the USGS has an extra tab for this event - the ShakeAlert® result!

ShakeAlert is the earthquake early warning system for the US West coast.

1/
earthquake.usgs.gov/earthquakes/ev… This is how earthquake early warning works.

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xkcd.com/723/
Mar 22, 2023 • 5 tweets • 2 min read
Been hearing a lot about earthquakes lately, and wondering if they're becoming more frequent?

No. Here is a record of all M>5 earthquakes recorded globally, by year since 1950 and by month since 2010. There are typically >100 M6+ earthquakes every year, and >1000 M5+!

1/ There are occasional spikes in the data - in the monthly data, the March 2011 Tohoku-Oki M9.1 earthquake creates a spike because of its many aftershocks.

2/
Mar 21, 2023 • 8 tweets • 3 min read
A M6.5 earthquake just occurred in Afghanistan, not far from where a M6.8 earthquake occurred in Tajikistan just last month - but with some critical differences.

1/ Image The two earthquakes in areas with subucting slabs oriented in opposite directions. The rainbow lines above represent the depth to the plate interface (red = shallow, blue = deep).

2/
Mar 20, 2023 • 17 tweets • 5 min read
A few weeks ago I looked at the Dead Sea Fault & noticed odd clusters of small earthquakes in Lebanon, persisting for years. Was this a feature of the fault system, I wondered?

No. A newly published paper gave me a hint.

1/
The authors of the new paper ("A fault-based probabilistic seismic hazard model for Lebanon, controlling parameters and hazard levels") noticed that in Lebanon, many more events are recorded during the day than at night.

2/
link.springer.com/article/10.100…
Mar 20, 2023 • 5 tweets • 2 min read
The M6.8 earthquake in Ecuador occurred directly below a fault separating the South American Plate from the North Andean Sliver - a right-lateral strike-slip fault moving ~9 mm/yr.

So it's a little startling that the earthquake looks LEFT-lateral.

1/
researchgate.net/publication/33… This aspect of the seismicity has been known for some time - the deeper earthquakes here are not on that shallow fault system, but rather an inferred boundary between two parts of the subducting slab.

2/
Mar 20, 2023 • 25 tweets • 7 min read
The area east of the Feb 6 double-rupture in Turkey was double-stressed: not one, but two large earthquakes terminated in this region, on parallel faults.

The East Anatolian Fault continues to the east, through Bingöl. What do we know about the seismic hazard here?

1/ In the map above, I've excluded the primary area of the recent rupture; what you're seeing is earthquakes recorded since 1900. Before ~1975, only large (M>5) earthquakes were recorded. Since then, seismic detection has been progressively improved.

2/
Mar 19, 2023 • 4 tweets • 2 min read
Recently some people have asked me if the trigger fault of the M7.8 is part of the Dead Sea Fault zone rather than the East Anatolian Fault zone. They are concerned because of the potential for a larger earthquake on the Dead Sea Fault Zone.

1/ It is true that this area has complex faults across a wide area. Personally, I am not so concerned about the labels - the important thing is which faults slipped, and how much.

2/
Mar 19, 2023 • 23 tweets • 5 min read
The western end of the Feb 6 M7.5 Turkey earthquake rupture (near Göksun) remains one of the most seismically active parts of the system.

Let's take a closer look.

1/ Aftershocks here are distributed across an area ~40 km x 50 km - we're not just looking at the main E-W fault, but at least two extra faults extending NW-SE and N-S down from the tip of the rupture. All of these faults have produced aftershocks.

2/
Mar 18, 2023 • 4 tweets • 2 min read
The tectonic setting of this earthquake is actually pretty unusual - to the north, the Nazca plate subducts steadily. To the south, it dives to ~80 km depth, then flattens out for 400 km before sinking again. The earthquake occurred near the upper bend.

1/ There have been many other earthquakes of M6.8+ in the broad area, but not so many at this depth - they are generally either shallower or deeper - and none specifically recorded near the latest epicenter.

2/
Mar 18, 2023 • 10 tweets • 4 min read
A M6.7 earthquake occurred below the city of Guayaquil, Ecuador today. This is a subduction zone - the Nazca plate is sinking below the South American plate - so earthquakes are not uncommon here.

1/
The reported depth of the quake is ~65-70 km, which pretty closely matches the plate boundary fault. However, the focal mechanism shows that the quake does not represent slip along the plate boundary, but instead is likely caused by breaking of the sinking plate.

2/
Mar 18, 2023 • 10 tweets • 2 min read
What does seismicity look like now around Gaziantep, located ~30 km ESE of the epicenter of the M7.8?

Aftershocks have diminished considerably, only rarely reaching M4. (Red earthquakes on the map & in the time series = events since March 1.)

1/ Image The aftershocks are largely located within the fault zone, not near Gaziantep, Kilis, or other cities to the east.

Compared to before the earthquake, the fault system is still quite noisy, producing up to ~10 earthquakes above M2.5 per day (see the histogram).

2/
Mar 14, 2023 • 18 tweets • 4 min read
If you're not an Earth scientist, you probably don't understand what this paper is about, starting with the title.

That is normal - and it isn't bad! - scientific results have to be communicated with technical language within the scientific community.

1/ Authors choose every word carefully so it says exactly what they mean; technical words have precise meanings, and each one may refer to a whole field knowledge.

Here is a brief summary in non-technical language about what this paper says:

2/
Mar 14, 2023 • 4 tweets • 1 min read
Where have aftershocks been occurring in the last week? This map shows seismicity since March 6 (red) with earlier aftershocks (gray). Mapped faults are in blue.

#TurkeySyriaearthquake

1/ The central part of the M7.8 (~Gaziantep) is pretty quiet now, and Hatay has only moderate seismicity.

Aftershocks are concentrated along the northern part of the ruptures, especially on the eastern (~Malatya) and western (~Göksun) ends.

2/
Mar 13, 2023 • 6 tweets • 2 min read
These are the aftershocks that have occurred near Adana so far (map is tilted, N is to the top right).

Scary, right? But it's important to keep them in perspective - M4 events have happened many times near Adana, without leading to a giant earthquake.

How do I know?

1/ This is the earthquake record near Adana. I had to scale down the aftershocks to show it - they are small compared to to the recorded events!

Of course, a larger earthquake is possible; M6+ events have been recorded, and this fault could produce even larger earthquakes.

2/