“Each of us has to decide what the right balance is between being effective and being honest.”
I was thinking of this quote whilst listening to Mustapha Meghraoui’s talk during this week’s ISEMG conference in Mugla (Turkey). Mustapha was reviewing the seismic hazard potential of the northern stretch of the Dead Sea Rift, and he ended by identifying two prominent areas where there was a substantial long-term (1000 yr) slip deficit that strongly suggested heightened future earthquake potential. The quote above has nothing to do with earthquakes. Neither is it by Mustapha. Instead, it relates to global warming and was from the climate modeller and policy advocate Stephen Schneider. Nevertheless, it struck me that what Schneider was wrestling with a decade or so ago with climate change has parallels to what some earthquake geologists are wrestling with now: what do we do when we believe that the science demands action? more
The 2011 Christchurch earthquake series had severe consequences and surprised scientists for many reasons. Ground motions were extremely strong despite the relative moderate magnitudes of the quakes (MW 5.3-7.1). The events happened on a system of hitherto unknown faults, some of which are located directly below Christchurch. Earthquake environmental effects (EEE), especially liquefaction, were intense and widespread. It turned out that subsequent quakes reactivated the same feeder dikes of sand blows, showing that saturated sediments are susceptible of liquefaction no matter if they had been liquefied recently (also see the paper of Quigley et al. (2013) on the liquefaction effects). Another stunning lesson was the occurrence of intense rockfall in the vicinity of Christchurch. In a recently published study, Mackey and Quigley (2014) dated rockfall boulders with 3He and show that they allow to estimate the recurrence intervall of local seismic events like the 2011 series. This works is a very interesting way to use EEE for paleo-earthquake studies. more
The M6.0 Napa earthquake came along with some interesting effects. It produced relatively large surface ruptures, but only minor secondary earthquake environmental effects like localized lateral spread, almost no liquefaction and rockfalls, but some hydrological changes. Dozens of geoscientists went out for mapping the earthquake ruptures, supported by InSAR data that precisely show where the ground moved.
Now the Geotechnical Extreme Events Reconnaissance (GEER) Association published a 400-pages report on their findings. The report is available for download here. Make sure to read it, it’s full of data and great photographs of surface ruptures.
Other interesting articles and posts on the Napa quake: more
In 2013 the Global Earthquake Model (GEM) –www.globalquakemodel.org – published seven Requests for Proposal covering topics related to the compilation of basic datasets as well as the creation and calculation of an updated probabilistic seismic hazard input model for South America. This initiative is now named the South America Risk Assessment Project (SARA).
Five consortia of South American researchers responded to this request and submitted proposals for the Hazard Component of SARA. These proposals has been recently endorsed by GEM and will constitute different datasets or topic layers for SARA. They include databases on historical and instrumental seismicity, hazardous faults (Quaternary deformation), tectonic geodesy and ground motions. more
On 24 September, 2013, a magnitude 7.7 earthquake occurred in Balochistan, Pakistan. The quake caused intense ground motions and had dramatic consequences – hundreds of people died, and more than 100,000 lost their homes. A secondary effect which caught much attention in the international media was the birth of an island off the Pakistani coast – Zalzala Jazeera or Earthquake Island. Another effect which went almost completely unnoticed was a small tsunami in the Arabian Sea. The tsunami reached wave heights of around 1 m at the Omani coast. In a paper which was recently published in Geology, my colleagues and me document the tsunami effects in Oman. We conclude on a submarine slide off Pakistan as the likely trigger mechanism.
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During the last three weeks I have been to Kazakhstan for paleoseismological field work and to summarize this journey: It was amazing! The trip was part of the Earthquakes without Frontiers project (EwF). This research project is funded by NERC and ESRC and aims on increasing the knowledge on earthquake hazards in Central Asia. The field work was lead by Richard Walker and scientists from Kazakhstan, Kyrgyzstan, and the UK had a close look at fault scarps in the easternmost parts of the country. Our aim was to determine the slip rates of some of the longest and most prominent thrust and strike-slip faults in the area. more
This summer and fall will be trenching time, our Belgian, Dutch and Austrian colleagues are opening paleoseismological trenches. The DEM/image of the last post by Christoph shows already some morphological relevant faults in the Aachen area (recognized by the rectangular open-pit lignite mines) that are striking NW-SE. more
Intraplate earthquakes are those that occur far away from plate boundaries in what is often also referred to as slowly deforming regions or stable continental regions (SCR). Seismicity there is comparably low and earthquake recurrence intervals can easily exceed thousands of years for individual faults. However, intraplate quakes do account for a significant number of earthquake fatalities and killed more people than those that happened at plate boundaries during the last 100 years (England & Jackson , 2011). A new book has been published a few days ago, dedicated to summarizing our knowledge of these seismic events. more
On 26 January and 3 February, 2014, two strong and shallow strike-slip earthquakes of magnitude 6+ occured beneath the island of Cephalonia in Western Greece. Both events caused intense damage to buildings and infrastructure. A team of Greek geologists mapped earthquake environmental effects (EEE) such as liquefaction, road failures, rock falls, small/medium size landslides and stonewall failures. The results are now published in a paper in Tectonophysics. more
Today (2014-05-24) on 09:25 UTC an earthquake with magnitude MW6.9 occurred in the NE Aegean Sea. The EMSC reports a depth of 27 km (USGS: 10 km). The quake had a (right-lateral) strike-slip mechanism and was felt as far away as Athens, Istanbul, and Sofia. More than 200 people were injured, most of them only lightly, and moderate damage to dozens of houses has been reported. The earthquake occurred on the (S)Western part of the North Anatolian Fault in the Samos Basin and was among the strongest events that have ever been recorded at that segment. more
