<P> Events with magnitudes greater than 4.5 are strong enough to be recorded by a seismograph anywhere in the world, so long as its sensors are not located in the earthquake's shadow . </P> <P> The following describes the typical effects of earthquakes of various magnitudes near the epicenter . The values are typical only . They should be taken with extreme caution, since intensity and thus ground effects depend not only on the magnitude, but also on the distance to the epicenter, the depth of the earthquake's focus beneath the epicenter, the location of the epicenter and geological conditions (certain terrains can amplify seismic signals). </P> <Table> <Tr> <Th> Magnitude </Th> <Th> Description </Th> <Th> Mercalli intensity </Th> <Th> Average earthquake effects </Th> <Th> Average frequency of occurrence (estimated) </Th> </Tr> <Tr> <Td> 1.0--1.9 </Td> <Td> Micro </Td> <Td> </Td> <Td> Microearthquakes, not felt, or felt rarely . Recorded by seismographs . </Td> <Td> Continual / several million per year </Td> </Tr> <Tr> <Td> 2.0--2.9 </Td> <Td> Minor </Td> <Td> I to II </Td> <Td> Felt slightly by some people . No damage to buildings . </Td> <Td> Over one million per year </Td> </Tr> <Tr> <Td> 3.0--3.9 </Td> <Td> III to IV </Td> <Td> Often felt by people, but very rarely causes damage . Shaking of indoor objects can be noticeable . </Td> <Td> Over 100,000 per year </Td> </Tr> <Tr> <Td> 4.0--4.9 </Td> <Td> Light </Td> <Td> IV to VI </Td> <Td> Noticeable shaking of indoor objects and rattling noises . Felt by most people in the affected area . Slightly felt outside . Generally causes none to minimal damage . Moderate to significant damage very unlikely . Some objects may fall off shelves or be knocked over . </Td> <Td> 10,000 to 15,000 per year </Td> </Tr> <Tr> <Td> 5.0--5.9 </Td> <Td> Moderate </Td> <Td> VI to VII </Td> <Td> Can cause damage of varying severity to poorly constructed buildings . At most, none to slight damage to all other buildings . Felt by everyone . </Td> <Td> 1,000 to 1,500 per year </Td> </Tr> <Tr> <Td> 6.0--6.9 </Td> <Td> Strong </Td> <Td> VIII to X </Td> <Td> Damage to a moderate number of well - built structures in populated areas . Earthquake - resistant structures survive with slight to moderate damage . Poorly designed structures receive moderate to severe damage . Felt in wider areas; up to hundreds of miles / kilometers from the epicenter . Strong to violent shaking in epicentral area . </Td> <Td> 100 to 150 per year </Td> </Tr> <Tr> <Td> 7.0--7.9 </Td> <Td> Major </Td> <Td> X or greater </Td> <Td> Causes damage to most buildings, some to partially or completely collapse or receive severe damage . Well - designed structures are likely to receive damage . Felt across great distances with major damage mostly limited to 250 km from epicenter . </Td> <Td> 10 to 20 per year </Td> </Tr> <Tr> <Td> 8.0--8.9 </Td> <Td> Great </Td> <Td> Major damage to buildings, structures likely to be destroyed . Will cause moderate to heavy damage to sturdy or earthquake - resistant buildings . Damaging in large areas . Felt in extremely large regions . </Td> <Td> One per year </Td> </Tr> <Tr> <Td> 9.0 and greater </Td> <Td> At or near total destruction--severe damage or collapse to all buildings . Heavy damage and shaking extends to distant locations . Permanent changes in ground topography . </Td> <Td> One per 10 to 50 years </Td> </Tr> </Table> <Tr> <Th> Magnitude </Th> <Th> Description </Th> <Th> Mercalli intensity </Th> <Th> Average earthquake effects </Th> <Th> Average frequency of occurrence (estimated) </Th> </Tr>

How strong of an earthquake to feel it