| 21. | There was a foreshock before the initial quake and another aftershock occurred ten days after the initial temblor.
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| 22. | A low-level alert was triggered by regional increases in seismicity ( later recognized as foreshocks ).
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| 23. | In other words, a plot of the cumulative number of foreshocks gets steeper just before the main shock.
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| 24. | This is because damaging aftershocks can occur after the initial quake, and rarely, it may be foreshock.
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| 25. | Several foreshocks preceded the main shocks and a series of aftershocks included two in the range of magnitude five.
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| 26. | They formed part of the foreshock sequence for the 1960 Valdivia earthquake, the largest recorded earthquake in history.
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| 27. | Seismologists define not only aftershocks but also foreshocks, tremors that are related to a major event but precede it.
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| 28. | The foreshock was not felt at Borusliqalan ( the westernmost village that was destroyed ) and the losses were high.
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| 29. | The foreshock that preceded Wednesday's main event by barely a minute and half was typical of many California earthquakes.
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| 30. | "Foreshock " and " aftershock " are relative terms, the United States Geological Survey emphasizes.
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