Seismic System Haiti, Port au Prince earthquake

Disadvantages of traditional maps of seismic hazard

Earthquake in Haiti sequential time showed that the traditional methods of constructing the map of seismic hazard contain significant methodological errors. On the traditional map of seismic hazard the capital of Haiti Port au Prince and cities west from it they were arranged in VI-VII to ball zone (see Fig.5a). During the earthquake dated January 12, 2010, M=7.2 the capital and these regions underwent action in the intensity IX- X (see Fig.5b). More than 3 million people proved to be in the hazardous zone, more than 150 thousands killed, to say nothing of material losses. Time already of the compilers of such maps would be to summon!!!

The traditional probabilistic maps of seismic hazard contain methodological errors due to misunderstanding of the real processes of preparation of strong earthquakes. For the inexperienced visitor recall that on the basis of these maps are designed building standards and rules.

Рис.5a. Рис.5b.

A new approach to build maps of seismic hazard

Our results show that segments of fault can not be viewed as a zones of separate elements, generating strong earthquakes with a certain recurrence and on this basis to build probabilistic maps. These elements are involved in the united process within the framework of SS. Thus, in the case of Haiti, the traditional approach of the last earthquake occurred 240 years ago, into 1770, and therefore, this zone at 50 summer repeatability of seismic hazard maps will not get into the danger zone. Conversely, the south-east of Cuba and island Jamaica considered seismically hazardous. To Fig.6 is given the generalized map of seismic danger for SS Haiti in the last 50 years, from which it is evident that only Dominican Republic and south of Haiti were located in the zone of possible earthquakes from M>6.9. The preparatory process of strong earthquakes is much more dynamic conventional representation (in the case of SS Haiti on average 30 years times). If the inside of the SS is fault, not manifested themselves in the modern instrumental observations (ag for 200-300 years), this does not mean that here is less seismic hazard. Under specific conditions of the track, there may be prepared by a strong earthquake in comparatively short time.

Fig.6.

Methodological recommendations

At mapping of seismic hazard on the basis of seismic entropy:

1. It should be clarified in some seismic system enters region under study.

2. The law Gutenberg-Richter frequency-magnitude earthquakes expected in the specific volume of the geological medium;in magnitude, which is not the law of Gutenberg-Richter, apply the law of seismic entropy production.

3. On the basis of seismic entropy to build dynamic maps of seismic hazard for the time windows from 3 months to 50 years. Accordingly, these maps will be renewed: 3 months time, 6 months time, etc.

4. Need to build dynamic maps of earthquakes expectations not only for land, but the ocean floor. This will build dynamic maps tsunami risk areas.

What practically it was possible done to reduce earthquake damage in Haiti on the basis of our method?

Let us fantasize and retrospectively model our recommendations and actions since 1960 for separately undertaken SS Haiti, into which enter poorly developed countries Cuba, Jamaica, Haiti and Dominican Republic. Already by 1965 becomes obvious, that preparations for Jamaica, Cuba and north of Haiti has not be conducted. Possible funding to strengthen buildings and facilities must be planned for the south of Haiti and east of the Dominican Republic. From 1995 to produce a real anti-seismic measures for cities Santiago and Santo Domingo. And from 2003 to redirect the efforts of long-term activities to strengthen buildings to the south of Haiti including Port au Prince. From 2007 to begin preparations with the medical staff, to prepare rescue services, conduct public education campaign, to create reserve of necessary products. Government organs plan to paint the events and actions in an emergency situation, provide for international collaboration, and the supply of primitive techniques for parsing debris on their own. Since the second half of 2008 to conduct training exercises in the case of an earthquake. Time of earthquake to predict, it is certainly impossible, but the localization problem in time and space and deliberate waste of funds and resources would be greatly to reduce the number of casualties and damage from the earthquake. This all could be done, without creating additional networks of observations, that are extremely important for weakly developed countries.

SS HAITI, Мs≥7.0

Retrospective forecast of earthquake Port au Prince.

And so by 2003 track approached a zone of instability C, but 2003.09.22 in the zone A occurred the indicator-earthquake (M6.4), which raised track. In SS Haiti seismic gap began, only static increase of entropy occurred. By August 2008 (with the enormous value of the entropy W=18.73) track approached the zone of instability C (1), determined on earthquakes 1770 and 1907 taking into account the real track of the preparation strong earthquake since 1956. Since September 2008 on the eastern segment of Enriquillo fault was prepared and it was expected strong earthquake with M=7.1-7.2. Earthquake occurred after the 1 year and 4 months. Was such correctness of forecast to the earthquake Port au Prince. On Fig.4 is given the dynamics of an increase in the probability of strong earthquake in SS Haiti in December 2009. The probability of earthquake was very high Р=85% (P_W=92%, P_K=92%) (see Fig.4).

The preparation of earthquake Port au Prince begins since 1956. In all this time the track of preparation strong earthquake was developed near the instability of zone C periodically approaching to zone A. Zone B was in the complete safety. By 2000 track from below went around the unstable regions of the earthquake 1946 and reached the values of entropy, which were not being observed in the last 300 years. This means that by 2000 the zones A and B were fully locked, as a result of which it occurred the slowing of movement of the micro-plate Gonave to the east, northeast with respect to the Caribbean plate. This led to the stress concentration on the eastern segment of Enriquillo fault and to left lateral strike-slip. Approximately the same mechanism was also for other earthquakes 1770 and 1907 EFZ. Closely to this scenario was observed at the preparation of earthquakes 1964 and 1983 in SS and subsystem Japan. These earthquakes occurred with the maximum values of entropy in itraplate zone in the west of Honshu, when the main zones of subduction were strengthened.

SS Haiti. For the development SS Haiti was used information about the strong earthquakes with 1700 until 1900, the catalogs of strong earthquakes from 1900 until 1970 and representative catalogs since 1970. Seismicity in the region is caused by complex interaction of Caribbean and North American plates as a result by which they were formed the micro-plate Gonave and Puerto Rico (PR) (see Fig.1).

Fig.1. Boundary region separating the Caribbean plate and the North America plate in area of Haiti (www.sciencedaily.com)

The motion of Caribbean plate to the east, northeast leads to the preferred left lateral strike-slip on faults of latitudinal stretch and to the thrust in the region PR. The existing information was insufficient for a allocation of the SS, but leaning on it and using our accumulated experience on other SS, it was revealed SS Haiti, was found responsible for the preparation of an earthquake on the Port au Prince. Fig.2 showes the SS Haiti, indicator-earthquakes and strong earthquakes.

In the SS identified three homogeneous seismotectonic zones with similar focal mechanisms: Septentrional Fault Zone (SFZ), Hispaniola Trough Zone (HTZ) and the Enriquillo Fault Zone (EFZ), contouring micro-plate Gonave from the east (zone A), north (zone B) and southern (Zone C) (see Fig.3).

The magnitudes of strong earthquakes (energy diagram) and zones of instability (track diagram) it is determined according to the law of seismic entropy production for W>15.5:

for zone А: Кs=0.41W + 9.17 К=0.41W + 8.59

for zone В: Кs=0.54W + 6.92 К=0.52W + 6.23 .

for zone С: Кs=0.08W + 14.30 К=0.46W + 7.47 (before Port au Prince earthquake) (1)

The average period of recurrence of strong earthquakes in the SS Haiti ~ 30 years.