Posts in the category »  Earthquake «  ( 123 Posts )

On 12 June, 2017, an earthquake with a magnitude of Mw6.3 occurred south of the island of Lesvos in Greece, damaged hundreds of buildings and claimed one life. The event ruptured a NW-SE trending normal fault and had a focal depth of 13 km. Our colleagues from the National and Kapodistrian University of Athens mapped the earthquake damage and the environmental effects that accompanied the earthquake. They found mass movements, secondary cracks, and report on a small tsunami. Their report can be downloaded here (PDF, 6 mb). For a higher-resolution file (33 mb), follow this link. Many thanks to Efthymios Lekkas for sending the report. more

In 2003 a devastating Mw 6.6 earthquake shook the city of Bam in the remote Kerman region of SE Iran, killing at least 31,000 people. This was one of the most destructive earthquakes on record in Iran, and racked up the fifth largest death toll of any earthquake since the year 2000. This blog post will focus on highlighting research which shows that even after this awful natural disaster, the hazard posed by faults in the area is likely to have remained high, contrary to many common assumptions.

Immediately following the Bam earthquake scientists scrambled to map the housing damage, surface fractures, aftershock patterns and co-seismic deformation to better understand the earthquake source [1][2]. One such study found that the structure responsible for the extreme shaking  at Bam was a previously unrecognised near-vertical strike-slip fault directly beneath the city, which ruptured between 2-8 km depth [3]. However, accurate aftershock locations suggested that the fault zone could generate earthquakes well below the base of the 2003 rupture patch, to nearly 20 km depth [4].

Slip distribution during the 2003 Bam earthquake and the associated aftershocks (white circles). The aftershocks are clearly occurring below the co-seismic rupture, suggesting the bottom half of the fault is seismogenic and unruptured.

The observation that only part of the seismogenic layer at Bam had ruptured in 2003 posed a series of important questions for the future seismic hazard in this already fragile region:

(1) Will post-seismic deformation mechanisms relax the stress changes generated by the 2003 earthquake on the fault surface aseismically?

(2) What is the future seismic hazard at Bam?

In a recent paper published in Geophysical Journal International, we have addressed these questions, as well as other topics of academic interest, by studying the post-seismic deformation after the Bam earthquake [5].

more

For quite some time (~7 years), I have been noticing that Holocene Dead Sea seismites frequently have a thin dark flat lying fine grained  layer of sediment on top. When I finally gained access to some electron microscopes at Cambridge University in 2013, I saw that these thin layers were very fine grained. After consultation with Dust Geologist Dr. Ken Pye, I came to the conclusion that they appeared to be proximal dust deposits. It was around that time that I realized that Dead Sea earthquakes probably kicked up dust clouds that then settled atop the seismite. An example of a dust cloud kicked up by an earthquake in Mexico is featured in my crowd funding pitch video (Jerusalem Quake Seasonality on Kickstarter ) and can be seen here (Mountain front dust clouds – Mexicali Quake of 2010 ). Christoph Gruetzner, who is also intrigued by the link between seismicity and dust, has accumulated a number of videos showing “dustquakes” on his YouTube channel[1]. more

Now that the new dates for the 8th PATA Days 2017 in New Zealand are fixed, it is time to bring to your attention an exceptional paper that was already published in 2016. I planned to write a review long time ago, but I just managed to do so now. The paper by Quigley et al. is not only likely to become your favourite read during the long flight to New Zealand, but it will also serve as an extremely valuable contribution to the study of earthquake environmental effects (EEEs) in general. The authors report on, and summarise, the effects that the 2010-2011 Canterbury earthquake sequence had on the environment. The paper is special in many ways: more

In microtidal seas such as the Mediterranean (tidal range ≈0.4 m sea-level indicators are commonly used to infer coseismic history. A list containing these indicators is long, including wave-cut platforms, marine terraces, displaced beach rock, biological agents, sedimentological and stratigraphical indicators, and archaeological indicators. Obviously, the trustworthiness varies a lot from one to another. For deriving late Holocene coastal tectonic activity, one of the most commonly used sea-level marker activity are tidal notches. These form distinct morphological and ecological erosional features developed within the tidal range [Pirazzoli, 1986; Antonioli et al., 2015]. more

The “Great 1117 Veronese Earthquake” was one of the strongest events that hit Northern Italy in historical times. Many aspects of this earthquake are still debated, but archaeological sources, historical archives, and geological records can help to better understand what had happened near Verona 900 years ago. On 20 January, 2017, a conference on the 1117 Veronese Earthquake took place in Venice, bringing together archaeologists, historians and earth scientists. The presentations were given in Italian, but Paolo Forlin from the Armedea project provides an English summary of the meeting. Read his highly interesting article here. more

If you are interested in visiting the epicentral areas of the recent earthquakes in the Central Apennines, Italy, this is your chance: A four days field trip will be held from 19-22 July, 2017, led by researchers who have studied the earthquake effects in detail. The trip focusses on the fault system that ruptured during the 1997 Umbria Marche, 2009 L’Aquila, and 2016 Norcia events. The trip is organised by scientists from Italy, France, UK, and Greece, and supported by a number of universities, state agencies, and INQUA, with the Università di Camerino as the main coordinator.

More information will be published soon. more

Annals of Geophysics has just published a special issue on the devastating Amatrice Earthquake series in Central Italy: Vol 59, Fast Track 5 (2016): The Amatrice seismic sequence: preliminary data and results.

The special issue, edited by Marco Anzidei and Silvia Pondrelli, contains lots of field reports, first assessments, and plenty of primary data. Plus, it’s all OPEN ACCESS! more

The M7.8 Kaikoura Earthquake in New Zealand produced one of the most complex ruptures ever observed, involving many different faults. Earthquake environmental effects include up to 10 m offset at the Kekerengu Fault, secondary ruptures, a tsunami, coseismic uplift, landslides and rockfalls, liquefaction, and maybe even earthquake lights. Lots of blogs and websites provide coverage on this earthquake, e.g. Geonet, the Landslide Blog, and The Trembling Earth. Our colleagues from the Research Group on Earthquake Geology in Greece worked on the landslides that happened during the earthquake. George Papathanassiou sent me the link to their Preliminary Map of Co-Seismic Landslides for the M 7.8 Kaikoura, New Zealand Earthquake. more

While the attention is still on the seismic sequence in Italy, a number of new papers have been published on paleoseismology, tsunamis, and active tectonics. Enjoy reading!

more