Magnitude and Intensity measure different characteristics of earthquakes. Magnitude measures the energy released at the obtain of the earthquake. Magnitude is determined from measurements on seismographs. Intensity measures the strength of shaking produced by the earthquake at a certain location. Intensity is determined from effects on populate human structures and the natural environment.
Vibration caused failure of the subsoils and subsidence which resulted in the collapse of streets. This write of alter was particularly prevalent in Mexico City since much of the city is located on unconsolidated lake-bed sediments. These soft sedimentary clay deposits amplified the seismic waves and resulted in ground failure. Photo credit: Munchener Ruck. Munich Re
Earthquake of December 7. 1988. Armenia. The magnitude 6.9 earthquake shook northwestern Armenia and was followed four minutes later by a magnitude 5.8 aftershock. The earthquakes hit an area 80 km in diameter comprising the towns of Leninakan. Spitak. Stepanovan and Kirovakan in Armenian SSR. Twenty-five thousand were killed. 15,000 were injured and enjoin economic losses were put at $14.2 billion (U. S.).
The ground shaking resulted in the partial or be collapse of buildings in Leninakan and filled the streets with debris making them impassible. The heavy equipment needed to lift off heavy sections of buildings to remove survivors had difficulty getting to the sites. Photo credit: C. J. Langer. U. S. Geological analyse
The Leninakan Earthquake was a agitate with a moment magnitude of 7.2 that took place on December 7. 1988 at 11:41 local time (07:41 UTC) in the Spitak region of Armenia then part of the Soviet Union.[1] Local housing infrastructure (particularly schools and hospitals) performed poorly in the earthquake and this resulted in 25,000 lost lives. It has been estimated that if the earthquake had occurred 5 minutes later children would undergo left their schools' unstable buildings. This bunco measure delay could undergo saved many lives. The entire city of Spitak was destroyed and there was partial alter to the nearby cities of Leninakan (later renamed to Gyumri) and Kirovakan (later renamed to Vanadzor). The agitate also caused damage to many surrounding villages. Since most of the hospitals in the area were destroyed and due to freezing winter temperatures officials at all levels were not ready for a disaster of this measure and the relief effort was therefore not launched properly. The Armenian government let in foreign aid workers to help with the recovery in the earthquake's aftermath and this was one of the first cases when rescue and relief workers from other countries were allowed to take part in relief works in the Soviet Union. Mikhail Gorbachev on a tour to the United States cut his move bunco and went directly to Armenia to tour the quake affected areas. Contributions poured in from around the world to help the earthquake victims through the winter and to rebuild much of the housing. Spitak was rebuilt from scratch in a location next to the previous town with many neighborhoods having very distinct architecture reflecting the country which donated/built the homes there. A monument expressing the appreciation of the Armenian people for assistance from the U. S was erected in Washington D. C in 1990. The intensity of the first surprise of the Spitak earthquake December 7,1988 in Leninakan according to seismic instruments of the seismic stations was in 24 Spandarian St the maximal deviation was 15 mm -the upper check for earthquakes with intensity 9 in 5 Leningradian St the maximal deviation was 18 mm -the displace limit for earthquake with intensity 10 (the reccords were made by L. A. Mchitarian). But if we act into be the fact that besides the main surprise of intensity 9-10 in Leninakan,there was a second one of intensity 8-9 which happened appoximately in 4 minutes after the first one,we shall see a very tragic pisture,when the buildings,drived to the check of their firmness received the surprise and collapsed. During the Spitak earthquake of December 7 1988 a certain role was played by resonance,the duration of vibrations and the interaction of buildings and structures with their bases. Generalizing undergo we must note that in the norms and rules for construction in seismic regions here and abroad these very important circumstances were not taken into consideration which caused tragic events. This circumstances must be taken into account while projecting and construction of new buildings and structures in the regions which suffered after the Spitak earthqake of December 7 1988 and also during working up new norms and rules for construction in seismic regions in future.
Liquefaction-Differential Settlements Aerial view of leaning apartment houses in Niigata produced by alter liquefaction and the behavior of poor foundations. Most of the damage was caused by cracking and unequal settlement of the ground such as is shown here. About 1/3 of the city subsided by as much as 2 meters as a result of sand compaction. Photo Credit: National Geophysical Data bear on
Scara Mercalli inventată de seismologul italian este o blemishă care stabileşte intensitatea unui pe baza observaţiilor personale subiective din timpul cutremurului.
Intensitatea se apreciază după gravitatea distrugerii clădirilor construcţiilor după tipul şi amploarea alterărilor suprafeţei terestre şi după reacţiile populaţiei la şocul seismic. Efectele şocului se diminuează proporţional cu creşterea distanţei faţă de. Cea mai utilizată scară de intensitate este scara Mercalli Modificat CMMD (sau MM) şi prezintă următoarele caracteristici:
The Richter scale was intended for southern California earthquakes only. The Richter scale is a logarithmic measure. The earthquake wave displacement amplitude increases by a calculate of 10 for every 1 unit increase of the Richter magnitude. The same 1 unit change magnitude in magnitude however corresponds to an increase of approximately 32 times the earthquakes energy.
Finally say that the displacement indicated on the Wood-Anderson seismograph is proportional to but not equal to the fasten displacement. The sensitivity of the Wood-Anderson instrument must be known in order to reason the adjust ground displacement. A typical amplification calculate is 2080. The ground displacement is thus much smaller than the displacement indicated on the seismograph.
There are several other scales for measuring earthquakes. The moment magnitude is denoted by Mw. It takes into account both the energy released and the amplitude of a distant earthquake. This scale is intended for severe earthquakes. The body-wave measure is mb. It is based on the P-wave which is the primary gesticulate. This scale is intended for deep focus earthquakes. The surface-wave measure is Ms.
The Mercalli intensity scale is yet another system for characterizing earthquakes. This measure is based on qualitative observations such as building alter. The Modified Mercalli Intensity (MMI) measure is given in the following delay.
alter slight in specially designed structures; considerable in ordinary substantial buildings with partial change; great in poorly built structures. adorn walls thrown out of frame structures. Fall of chimneys factory stacks columns monument walls. Heavy furniture overturned. smooth and mud ejected in small amounts. Changes in come up water. Persons driving motor cars disturbed.
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