The recent catastrophic earthquake in L’Aquila from Italy’s Abruzzo region that has also damaged many medieval, Renaissance and Baroque buildings, brings back to many people in Romania the grim memories of the big 1977 Romanian earthquake (7.2 Richter scale magnitude), which destroyed in as little as 1 minute an important number of old and new buildings throughout the entire country and killed more than 1,500 people.
Neo-Romanian style building damaged in the 1977 earthquake, Magheru Boulevard - Italian Church area, Bucharest (©Valentin Mandache)
The nightmare was briefly reawakened by another short earthquake that struck Romania a few days ago on 25 April, which fortunately was very short and of moderate magnitude (5.3 Richter at the epicentre), without causing victims or damage.
I was a witness of the big 1977 earthquake and its terrible consequences, then also studied the phenomenon as part of my coursework and training as a geophysicist at the University of Bucharest in late 1980s and later worked as a seismics specialist for a big oil exploration contractor in Britain, facts which I believe qualify me to give you in this article an informed view on the earthquake risk faced by the large stock of period buildings from Romania’s capital.
Most of the period houses of Bucharest and from the rest of Romania for that matter are vulnerable to earthquakes over 5.5 degree magnitude. Historical data spanning the last millennium, gathered from medieval chronicles, archive sources, etc. indicate a rate of 2 – 3 catastrophic events, defined as over 7.0 degree Richter magnitude, per century.
Unlike the Italian mainland earthquakes which are of shallow depth and thus highly localised, the Romanian ones occur at depths between 70 -180 km, their effect being felt over large distances from the epicentre, which is situated in the Vrancea region of central Romania. Their origin is the collision and friction in that area between three regional tectonic plates, a sector of the larger system formed by the collision in southern Europe between the major African, European and also Arabian tectonic plates, which in the course of geological times formed the mountainous chains that include the Alps, the Carpathians or the Caucasus.
Vrancea seismic region (red colour)- located at the triple junction point of regional tectonic plates that converge in that area (map source: Romanian National Institute for Earth Physics; tectonic plate delineation: V. Mandache)
Explained in basic terms, that triple junction point of tectonic plates is a rare occurrence in geological terms, making the geological movements more numerous and dynamic compared with the ususal collision between just two plates, as can be seen on the map above that shows in red colour the high density of earthquakes in the Vrancea region. The seismic waves are also propagated and even intensified by the blanket of sediments (sandstone, gravel or clay washed up by the rivers and deposited in the plains that surround the Carpathian Mountains), acting like a huge resonance box for the earth tremors, in the same manner as sound waves are amplified in the resonance box of a string musical instrument.
Bucharest is located in the middle of one of those plains, being directly exposed to the seismic waves generated 150 km away in Vrancea. The damage caused by many intermediate-depth earthquakes is therefore extremely severe.
The property bubble of the last four years has made Bucharest period properties some of the most expensive in the entire European Union, even more expensive than superior examples in the United Kingdom or France. The euphoria induced by the bubble, coupled with the unrealistic expectations of both seller and estate agent, induced them to casually ignore or just wipe under the carpet obvious facts such as these properties’ bad state of repair or the fact that many went through three catastrophic earthquakes in the last century (1908, 1940 and 1977). The prospect of quick undeserved gains continues to make them considering trivial a multitude of other details, such as the fact that many period houses are built on the unstable old floodplain of the Dambovita river, on shallow inadequate foundations and put toghether from questionable quality materials, provided with low earthquake resistance structures.
The shallow foundations, on a rubble filled ground, of a 19th century Lipscani area building seen in a recent archaelogical dig. Bucharest 2009 (©Valentin Mandache)
The majority of Bucharest period buildings were erected between mid-19th and mid-20th century (see my previous post on the history of the building booms of Bucharest with the largest proportion of them affected by at least two catastrophic earthquakes, those that took place in 1940 and 1977.
The 1940 event badly affected the Cotroceni Royal Palace, the official residence of the king, a beautiful edifice in French Continue reading