From temblor: “Albania earthquake strikes highest-hazard zone in the Balkans, devastating nearby towns”
November 26, 2019
by Ross S. Stein, Ph.D., and Volkan Sevilgen, M.Sc., Temblor, Inc.
As of today, some 24 people are dead and 650 injured, and many more are unaccounted for in collapsed concrete buildings on the coastal plains surrounding the epicenter. The quake likely struck on a ‘blind thrust fault’ that does not reach the Earth’s surface but had nevertheless been previously identified by geologists.
It could have been worse
On 26 Jul 1963, some 165 km (100 mi) east of the 26 Nov 2019 Mag. 6.4 Albania shock, a Mag. 6.1 earthquake struck Skopje, capital of Northern Macedonia destroying 80% of the city, killing over 1,070 people, injuring 3,000-4,000, and leaving more than 200,000 people homeless.
It would appear that the 26 Nov 2019 quake, although 5 times larger than the Skopje event, did much less damage, perhaps because it struck more than 35 km from the 375,000 people living in the Albanian capital of Tirana.
Map showing Temblor’s globally consistent PUSH (Probabilistic Uniform Seismic Hazard) model, together with earthquakes principally from the EMSC catalog. The region is one in which residents should expect powerful shaking in their lifetimes. The aftershock distribution is roughly perpendicular to the presumed NW-SE oriented thrust fault.
Immediate foreshocks and remote aftershocks
The M 6.4 quake was preceded during the previous 6 hours by four M3 shocks in the epicentral region, the largest of which was Mag. 4.4, striking 1 hour before the mainshock. While uncommon, this kind of activity does not make earthquake prediction any easier, because the foreshocks do not show any features that would distinguish them from typical shocks. Perhaps more surprising, there was a burst of seismicity 230 km (140 mi) to the northwest of the M 6.4 a little over 6 hours later near the city of Mostar in Bosnia and Herzegovina, capped by a Mag 5.4 shock. This might be a coincidence, but if these two distant events are indeed related, it would have to be by the stresses carried by the seismic waves of the M 6.4, which dissipate within several minutes.
Could the Mag. 5.4 shock be a remotely triggered aftershock of the M 6.4? There is likely no smoking gun, but the possibility is nevertheless tantalizing.
A long history of large earthquakes
The high earthquake hazard of coastal Albania stems from tectonic compression of the crust that extends from Croatia south to Greece. The compression is evident in the contraction of the Earth’s surface measured by GPS, and by the long history of large earthquakes in the region. In fact, the southern Balkans are more seismically active than Italy.
Figure from Sevilgen et al. 2014 showing the ‘EMEC’ instrumental and historical earthquake catalog (Grünthal and Wahlström, 2012). The earthquake catalog extends to AD 1000; however, it is incomplete until about the past century, meaning that not all M≥5.5 quakes were recorded due to lack of seismometer coverage. But even when restricted to that time period (red shocks), the site of the 25 Nov 2019 quake is among the most active anywhere in the Balkans or Italy.
Blind thrust fault a likely culprit
The contraction has produced a series of thrust faults, only some of which come to the surface. Those that do not cut the Earth’s surface instead fold the overlying strata. Croatia’s coastal islands are one example of these folds, and one of these folds lies at the epicenter of the 26 Nov 2019 quake.
Koci et al. (2011) and Kastelic et al. (2016) identified active faults in the region for the European SHARE project using satellite imagery and field mapping (with inferred fault slip rates in black numerals), and they subsequently remapped the region (revised fault slip rates in red numerals; Sevilgen et al., 2014). One can see that thrust faults near the 26 Nov 2019 epicenter are about 75 km long with slip rates of ~1 mm/yr. That would mean that M~6.4 quakes on these faults would have mean inter-event times of roughly 500-1,000 years.
Amplified shaking on the coastal plains
The shaking produced by the Mag. 6.4 shock was almost certainly amplified in the weak, unconsolidated basins and coastal estuaries surrounding the epicenter. Temblor’s STAMP model shows amplification factors of 4-5 over the shaking that was experienced at bedrock sites, such as at the epicenter itself. Compounding the weak soil are water-saturated coastal plains, which are susceptible to liquefaction. This is where the soil turns to quicksand, causing buildings to sink or tilt. Sandblows and eruptions of artesian water often accompany shaking in such regions, compounding the damage.
Temblor’s STAMP high resolution (200 m) model of site amplification reveals that in Thumanë, Durres, and Lezhe, the shaking could have been severely amplified, contributing to the damage of weak buildings. Areas in black likely shook four times higher than those in yellow. The black areas are water-saturated coastal estuaries and plains that might also liquify when shaken violently, which can cause buildings to sink and tilt, rendering them a total loss. The fault on which the Mag. 6.4 quake struck is probably concealed by a growing fold.
Undoubtedly, emergency responders, geologists, and seismologists will learn more about this quake in the days to come. But what we can say now is that the hazard was not unforeseen.
References
Grünthal, G. and Wahlström, R. (2012): The European‐Mediterranean Earthquake Catalogue (EMEC) for the last millennium, Journal of Seismology, 16, 3, 535‐570, doi: 10.1007/s10950‐012‐9302‐y
Vanja Kastelic, Michele M.C. Carafa, and Francesco Visini (2016), Neotectonic deformation models for probabilistic seismic hazard: a study in the External Dinarides, Geophysical Journal International, 205, 1694–1709, https://doi.org/10.1093/gji/ggw106
R. Koci, N. Kuka, V. Kuk, K. Kuk, J. Mihaljevic, B. Glavatovic, H. Hrvatovic, I. Brlek, S. Kovacevic, S. Radovanovic, Z. Milutinovic, R. Salic (2011), Seismotectonic model as the OHAZ input, in Harmonization of Seismic Hazard Maps for the Western Balkan Countries, Closing Meeting Zagreb, 12-13 May 2011 (mihaljevic@seismo.co.me)
Volkan Sevilgen , R.A. Bennett , I. Brlek , Laurentiu Danciu , V. Kastelic , S. Kovacevic , C. Kreemer , K., Kuk , N. Kuka , Z. Milutinovic , S. Mustafa , B. Sket-Motnikar , Ross S. Stein , and L. Vucic (2014), BALKANS-OQ: A collaborative seismic hazard assessment of the Balkan countries using the OpenQuake software and the GEM Strain Rate Model, Second European Conference on Earthquake Engineering and Seismology, Istanbul, http://www.eaee.org/Media/Default/2ECCES/2ecces_esc/3276.pdf
See the full article here .
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Please help promote STEM in your local schools.
Stem Education Coalition
Earthquake Network project
Earthquake Network is a research project which aims at developing and maintaining a crowdsourced smartphone-based earthquake warning system at a global level. Smartphones made available by the population are used to detect the earthquake waves using the on-board accelerometers. When an earthquake is detected, an earthquake warning is issued in order to alert the population not yet reached by the damaging waves of the earthquake.
The project started on January 1, 2013 with the release of the homonymous Android application Earthquake Network. The author of the research project and developer of the smartphone application is Francesco Finazzi of the University of Bergamo, Italy.
Get the app in the Google Play store.
Smartphone network spatial distribution (green and red dots) on December 4, 2015
Meet The Quake-Catcher Network
The Quake-Catcher Network is a collaborative initiative for developing the world’s largest, low-cost strong-motion seismic network by utilizing sensors in and attached to internet-connected computers. With your help, the Quake-Catcher Network can provide better understanding of earthquakes, give early warning to schools, emergency response systems, and others. The Quake-Catcher Network also provides educational software designed to help teach about earthquakes and earthquake hazards.
After almost eight years at Stanford, and a year at CalTech, the QCN project is moving to the University of Southern California Dept. of Earth Sciences. QCN will be sponsored by the Incorporated Research Institutions for Seismology (IRIS) and the Southern California Earthquake Center (SCEC).
The Quake-Catcher Network is a distributed computing network that links volunteer hosted computers into a real-time motion sensing network. QCN is one of many scientific computing projects that runs on the world-renowned distributed computing platform Berkeley Open Infrastructure for Network Computing (BOINC).
The volunteer computers monitor vibrational sensors called MEMS accelerometers, and digitally transmit “triggers” to QCN’s servers whenever strong new motions are observed. QCN’s servers sift through these signals, and determine which ones represent earthquakes, and which ones represent cultural noise (like doors slamming, or trucks driving by).
There are two categories of sensors used by QCN: 1) internal mobile device sensors, and 2) external USB sensors.
Mobile Devices: MEMS sensors are often included in laptops, games, cell phones, and other electronic devices for hardware protection, navigation, and game control. When these devices are still and connected to QCN, QCN software monitors the internal accelerometer for strong new shaking. Unfortunately, these devices are rarely secured to the floor, so they may bounce around when a large earthquake occurs. While this is less than ideal for characterizing the regional ground shaking, many such sensors can still provide useful information about earthquake locations and magnitudes.
USB Sensors: MEMS sensors can be mounted to the floor and connected to a desktop computer via a USB cable. These sensors have several advantages over mobile device sensors. 1) By mounting them to the floor, they measure more reliable shaking than mobile devices. 2) These sensors typically have lower noise and better resolution of 3D motion. 3) Desktops are often left on and do not move. 4) The USB sensor is physically removed from the game, phone, or laptop, so human interaction with the device doesn’t reduce the sensors’ performance. 5) USB sensors can be aligned to North, so we know what direction the horizontal “X” and “Y” axes correspond to.
If you are a science teacher at a K-12 school, please apply for a free USB sensor and accompanying QCN software. QCN has been able to purchase sensors to donate to schools in need. If you are interested in donating to the program or requesting a sensor, click here.
BOINC is a leader in the field(s) of Distributed Computing, Grid Computing and Citizen Cyberscience.BOINC is more properly the Berkeley Open Infrastructure for Network Computing, developed at UC Berkeley.
Earthquake safety is a responsibility shared by billions worldwide. The Quake-Catcher Network (QCN) provides software so that individuals can join together to improve earthquake monitoring, earthquake awareness, and the science of earthquakes. The Quake-Catcher Network (QCN) links existing networked laptops and desktops in hopes to form the worlds largest strong-motion seismic network.
Below, the QCN Quake Catcher Network map
ShakeAlert: An Earthquake Early Warning System for the West Coast of the United States
The U. S. Geological Survey (USGS) along with a coalition of State and university partners is developing and testing an earthquake early warning (EEW) system called ShakeAlert for the west coast of the United States. Long term funding must be secured before the system can begin sending general public notifications, however, some limited pilot projects are active and more are being developed. The USGS has set the goal of beginning limited public notifications in 2018.
Watch a video describing how ShakeAlert works in English or Spanish.
The primary project partners include:
United States Geological Survey
California Governor’s Office of Emergency Services (CalOES)
California Geological Survey
California Institute of Technology
University of California Berkeley
University of Washington
University of Oregon
Gordon and Betty Moore Foundation
The Earthquake Threat
Earthquakes pose a national challenge because more than 143 million Americans live in areas of significant seismic risk across 39 states. Most of our Nation’s earthquake risk is concentrated on the West Coast of the United States. The Federal Emergency Management Agency (FEMA) has estimated the average annualized loss from earthquakes, nationwide, to be $5.3 billion, with 77 percent of that figure ($4.1 billion) coming from California, Washington, and Oregon, and 66 percent ($3.5 billion) from California alone. In the next 30 years, California has a 99.7 percent chance of a magnitude 6.7 or larger earthquake and the Pacific Northwest has a 10 percent chance of a magnitude 8 to 9 megathrust earthquake on the Cascadia subduction zone.
Part of the Solution
Today, the technology exists to detect earthquakes, so quickly, that an alert can reach some areas before strong shaking arrives. The purpose of the ShakeAlert system is to identify and characterize an earthquake a few seconds after it begins, calculate the likely intensity of ground shaking that will result, and deliver warnings to people and infrastructure in harm’s way. This can be done by detecting the first energy to radiate from an earthquake, the P-wave energy, which rarely causes damage. Using P-wave information, we first estimate the location and the magnitude of the earthquake. Then, the anticipated ground shaking across the region to be affected is estimated and a warning is provided to local populations. The method can provide warning before the S-wave arrives, bringing the strong shaking that usually causes most of the damage.
Studies of earthquake early warning methods in California have shown that the warning time would range from a few seconds to a few tens of seconds. ShakeAlert can give enough time to slow trains and taxiing planes, to prevent cars from entering bridges and tunnels, to move away from dangerous machines or chemicals in work environments and to take cover under a desk, or to automatically shut down and isolate industrial systems. Taking such actions before shaking starts can reduce damage and casualties during an earthquake. It can also prevent cascading failures in the aftermath of an event. For example, isolating utilities before shaking starts can reduce the number of fire initiations.
System Goal
The USGS will issue public warnings of potentially damaging earthquakes and provide warning parameter data to government agencies and private users on a region-by-region basis, as soon as the ShakeAlert system, its products, and its parametric data meet minimum quality and reliability standards in those geographic regions. The USGS has set the goal of beginning limited public notifications in 2018. Product availability will expand geographically via ANSS regional seismic networks, such that ShakeAlert products and warnings become available for all regions with dense seismic instrumentation.
Current Status
The West Coast ShakeAlert system is being developed by expanding and upgrading the infrastructure of regional seismic networks that are part of the Advanced National Seismic System (ANSS); the California Integrated Seismic Network (CISN) is made up of the Southern California Seismic Network, SCSN) and the Northern California Seismic System, NCSS and the Pacific Northwest Seismic Network (PNSN). This enables the USGS and ANSS to leverage their substantial investment in sensor networks, data telemetry systems, data processing centers, and software for earthquake monitoring activities residing in these network centers. The ShakeAlert system has been sending live alerts to “beta” users in California since January of 2012 and in the Pacific Northwest since February of 2015.
In February of 2016 the USGS, along with its partners, rolled-out the next-generation ShakeAlert early warning test system in California joined by Oregon and Washington in April 2017. This West Coast-wide “production prototype” has been designed for redundant, reliable operations. The system includes geographically distributed servers, and allows for automatic fail-over if connection is lost.
This next-generation system will not yet support public warnings but does allow selected early adopters to develop and deploy pilot implementations that take protective actions triggered by the ShakeAlert notifications in areas with sufficient sensor coverage.
Authorities
The USGS will develop and operate the ShakeAlert system, and issue public notifications under collaborative authorities with FEMA, as part of the National Earthquake Hazard Reduction Program, as enacted by the Earthquake Hazards Reduction Act of 1977, 42 U.S.C. §§ 7704 SEC. 2.
For More Information
Robert de Groot, ShakeAlert National Coordinator for Communication, Education, and Outreach
rdegroot@usgs.gov
626-583-7225
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