Global Analysis of the Earth's Seismic Activity since the 80'S and General Lessons Learnt

The paper assesses the possible increased tendency of earthquake activity (normal is considered that the Earth seismic activity is almost constant in terms of number of earthquakes per decade for a corresponding magnitude), revealed after studying the frequency of the major earthquakes magnitudes recorded since the 80's world over. The results indicated an unusual increased seismic activity, since the 90's, which is in contradiction with the generally constant trend of the previous decades. In order to clarify the cause of the unusual increased trend of the earthquakes frequency in certain periods of times after the 90's, some considerations are presented, based on a detailed review of the recent major earthquakes, such as Kobe-Japan (1995), Molise, Puglia-Italy (2002), Bam-Iran (2003), Sumatra – Andaman Islands (2004), Kashmir-Pakistan (2005) and South of Java – Indonesia (2006). A common fact was that all these events surprised the local population as well as local and national level risk managers, because the hit areas were not considered before specific historically earthquake prone zone, so the building codes were not updated for a real seismic zone (including major cities as Kobe and Islamabad). The seismic analysis is accompanied by general lessons for risk managers involved in the activities of updating and implementing the building codes, seismic risk zoning and regulation, in order to avoid in the future any other misjudges of the earthquakes hazard, for minimizing the loss of human lives and material damages.