NH
Natural Hazards

Earthquake hazard

The CRED presents the bill: the socio-economic cost of natural disasters.

The CRED presents the bill: the socio-economic cost of natural disasters.

Which type of natural disaster is the most frequent? And which one causes the largest economic losses? Which populations are mainly affected? What are the necessary steps to reduce natural disasters’ impact? If you have ever wondered about any of these questions, you’d be interested to know that there is an institute answering all of them with a series of reports and ad hoc publications.

We are talking about the Centre for Research on the Epidemiology of Disasters (CRED). The CRED is based, since 1973, at the Université Catholique de Louvain in Belgium and since 1980 it’s a collaborator of the World Health Organization (WHO). Their main goal? Study public health during a mass emergency as well as the structural and socio-economic impact of natural and technological disasters and human conflicts. They maintain the world’s most comprehensive database (EM-DAT) on occurrence and effects of technological and natural disasters from 1900 to the present day: more than 22,000 events and counting. [Read More]

Earthquake-induced landslides and the ‘strange’ case of the Hokkaido earthquake

The population of many countries in the world is exposed to earthquakes, one of the most destructive natural hazards. Sometimes, consequent triggered  phenomena can be even worse than the earthquake itself. In this context, earthquake-induced landslides often concur in life and economic losses. To better understand these induced phenomena, updated catalogues of their types and location of occurrence are fundamental. In his works, Dr David K. Keefer performed several interesting statistical analysis, which highlighted how the magnitude and the distance from the epicentre play a key role in triggering earthquake-induced landslides (Figs. 1 and 2). In particular, he showed that the number of landslides induced by earthquakes decreases with the increase in distance from the epicentre (Fig.1) and that the number of landslide increases with larger magnitude events (Fig. 2). [Read More]

How to study Mega-earthquakes? By generating them!

Dr. Francesca Funiciello

Francesca Funiciello is an Associated Professor at Roma Tre University (Rome, Italy). Her research interests are, among others, geodynamics, seismotectonics, rheology of analogue materials and science communication. She leads an active and young research group composed by Fabio Corbi, Silvia Brizzi and Elenora van Rijsingen, and collaborates with many other young and experienced researchers in Europe. The main activities of Francesca, Fabio, Silvia and Elenora involve analogue and numerical modelling of subduction zones, geophysical data analysis and geostatistics in the field of mega-earthquakes.

 

 

  1. Hi guys, can you tell us a bit more about “mega-earthquakes” and why it is so important to study them?

The interface between the subducting and overriding plates (Fig.1), the so-called megathrust, hosts the largest earthquakes on our planet Earth. They are generally called mega-earthquakes, with the prefix ‘mega’ highlighting both the fault originating them and their size. A quite recent example of a mega-earthquake is the Sumatra-Andaman event that occurred in 2004. The length of the fault that ruptured was ca. 1000 km and it generated a magnitude in the range of Mw 9.1–9.3 (Lay et al., 2005; Stein & Okal 2005; Subarya et al., 2006; Fujii & Satake 2007), where Mw denotes moment magnitude, a logarithmic measure of earthquake size. There had not been an event so large since the 1964 Alaska earthquake. The energy released during the Sumatra-Andaman 2004 event was in the range 5–10×1022 Nm—equivalent to the sum of the moment of all earthquakes in the preceding decade, worldwide (Lay et al., 2005).

 

Figure 1 – Schematic section through a subduction zone. The interface between the overriding and subducting plate is the so-called megathrust. The red star highlights the hypocenter of a megathrust earthquake (courtesy of S. Brizzi).

 

Subduction mega-earthquakes (together with the tsunamis they may generate) are among the largest hazards for human life, considering that millions of people live in proximity of subduction zones (e.g., the NE-Japanese and South American subduction zones), which are located at the edges of the Pacific Ocean.

 

  1. Which approach does the scientific community adopt to study mega-earthquakes? 

[Read More]