Următorul M7 Optiuni

[shapeshifter]

Image of Next Earthquake:

Epicenter: 45.6+-0.1 N, 26.6 +-0.1 E
Epicentral Area: 50km in NE-SW Direction and 20 km width
Rupture: Uni-Lateral Toward SW
Depth Range: 140 –160 km
Magnitude: M=7.3+-0.4
Time: 2007+-6

„A long-term earthquake prediction, based on the regularity of earthquake occurrences and a seismic gap theory, is presented. Especially in subduction zones, clear geophysical background (plate tectonics) and short recurrence time allow us to make practical use of the prediction. An M7 intermediate-depth earthquake occurs in the Vrancea region of Romania on average every 20 to 30 years. The last major earthquake occurred in 1986 (M7.2). According to the average rate frequency, we expect a next large earthquake will occur soon. Although a long-term prediction based on regularity of earthquake occurrences has already been carried out by Purcaru (1974) and Enescu et al. (1974), and the predicted M7 earthquake actually occurred in 1977, this prediction was not based on the seismic gap theory and the hypocenter could not have been precisely predicted. Here we show (i) that we can relocate earthquakes since 1934 quite accurately by using the modified joint hypocenter determination method developed by Hurukawa & Imoto (1992), and (ii) that past M7 class earthquakes had occurred at a depth range of 60-140 km with no overlapping of the aftershock areas, and the area at 140-160 km depth remains unbroken. Considering three seismic active time bands in each century characterized by “quasicycles“ of about 100 year identified by Purcaru (1979), and the relocation results, we propose a hypothetical scheme for the occurrence of the M7 Vrancea earthquakes, as follows: a first M7 earthquake occurs in the deeper segment (140-160 km in depth) at the beginning of each century (years 0-10), then a second M7 earthquake occurs in the midst segment (110-140 km in depth) at the midst of each century (years 30- 40), and finally a third M7 earthquake occurs in the shallower segment (80-110 km in depth) at the end of each century (years 70-90). Certainly, the focal depth of old earthquakes is not accurate, since it is estimated from seismic intensity distribution.However, historical M7 earthquakes show a clear dependence of focal depth on the particular active time interval in each century.
Purcaru (1974, 1979), Enescu et al. (1974) and Enescu & Enescu (1996, 1999) predicted from the regularity of earthquake occurrence that the next major Vrancea earthquake will occur in this decade. Considering the result of this study and the periodicity of the seismic activity over the past 1000 years, we believe that the possibility of the next M7 earthquake occurring at a depth of 140-160 km by 2010 is very high.” (N. Hurukawa, M. Popa, M. Radulian)

Acest topic a fost editat de shapeshifter: 28 Jun 2009, 06:27 PM

[shapeshifter]

Cum se manifesta un cutremur din Vrancea ?
Cred ca e util sa evidentiem aici modul cum se manifesta un seism vrancean, mai bine zis modul cum resimtim noi miscarea seismica, in special atunci cand ne aflam intr-o cladire, la birou, acasa, intr-un supermarket, la scoala etc. In primul rand, vom mentiona ceea ce simtim de fapt, cum percepem miscarea si la ce trebuie sa ne asteptam cand sesizam un anumit tip de miscare. Eventual voi corela aceste aspecte cu sosirea anumitor tipuri de unde.
Experienta cutremurelor precedente pe care le-am simitit eu (1986, 1990, 2004, precum si a unor seisme de mai mica magnitudine), impreuna cu ceea ce mi s-a relatat de catre cunoscuti, rude, persoane mai in varsta, in legatura si cu seismul din 1977, si chiar cu cele 2 cutremure din anul 1940, arata urmatoarele lucruri importante si interesante, cred eu.
Cutremurul incepe intotdeauna cu o miscare verticala, un saltat brusc, saltat care poate fi mai intens sau mai slab, in functie de marimea cutremurului. In cazul seismelor mici (in jur de 5,0 pe scara Richter), acest saltat initial nu este perceput in majoritatea cazurilor; in conditii speciale (liniste in camera, stat pe scaun, etaj superior) s-ar putea simti o mica trepidatie, ceva discret, eventual ai o impresie vaga, neclara (si remarci "mi s-a parut..."); in cazul seismelor de magnitudine medie (in jur de 6-6 si ceva pe scara Richter), am putut simti si inceputul cutremurului, manifestat ca miscare verticala, dar care nu era totusi foarte intensa, se simtea ca vibreaza un pic podeaua, un usor saltat. In cazul seismelor majore (de magnitudine peste 7,0), saltatul initial este mai puternic, daca esti in interiorul cladirii simti destul de clar "impingerea verticala", e ca si cum vecinul de deasupra tranteste cu putere un obiect greu pe podea, ca si cum ar rasturna un sifonier, se simte clar. Acesta este inceputul seismului, si, asa cum spuneam, dupa cat de intensa este aceasta miscare verticala, putem banui daca e vorba despre un cutremur major sau unul de magnitudine medie. Dupa un numar de secunde de la saltatul initial (15-20, depinde de momentul in care constientizam, daca percepem respectiva miscare verticala), incepe un balans, o miscare orizontala, care devine puternica in faza maxima a cutremurului; de fapt, in faza maxima putem simti chiar o combinatie de miscari, in principal orizontale, dar nu lipsesc nici cele pe verticala. Urmeaza faza de atenuare pana sub limita de percepere umana, desi seismografele vor inregistra in continuare undele, timp de mai multe minute.
Important este sa intelegem ce putem face din momentul in care simtim acel saltat rau-prevestitor si momentul amplificarii miscarii seismice, la faza maxima. E adevarat, de asemeni, ca ceea ce simtim depinde mai ales de reactia cladirii la miscarea terenului, dar eu m-am referit la situatiile in care ne aflam in interiorul unei cladiri.

Oricum, trebuie retinuta succesiunea: saltat initial, o aparenta atenuare, apoi amplificare cu o miscare orizontala puternica, si chiar combinatie de miscari ondulatorii, apoi atenuare pana la incetarea perceperii miscarii.
Evident, nu e sigur ca vom simti saltatul incepator, fiindca situatiile in care ne putem afla in momentul producerii unui cutremur puternic pot fi diverse. Daca simtim deja miscare orizontala, inseamna ca suntem foarte aproape de sau in plina faza maxima a cutremurului.


Mai jos este Filmuletul de la cutremur din timpul concertului de la Atheneul Roman. Se poate observa acea tresarire destul de puternica pe verticala de la inceputul cutremurului. Cred ca miscarea asta pe verticala a fost principala manifestare a acestui seism, cel putin asa s-a vazut pe acest filmulet din interiorul Atheneului Roman.

http://www.youtube.com/watch?v=a9HQdBG5jrE

cutremur.net

Acest topic a fost editat de shapeshifter: 6 Jul 2009, 04:03 PM