Word: seismicly
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...sudden cracking and expansion of rock along a fault zone in the earth when stresses reach a critical point. This cracking creates many tiny cavities in the water-saturated rock. That slows the passage of P (pressure) waves, which travel faster through liquid-filled cracks. Another kind of seismic wave, the S (shear) wave, however, is less affected by the newly opened cracks; thus the usual ratio of P-to S-wave velocity drops sharply. Then, as ground water gradually seeps into the new cracks, the ratio returns to normal. But the water increases pressure within the rock, causing...
That possibility is based upon studies of the two basic types of seismic waves that are given off by all earthquakes: 1) P (or pressure) waves, which alternately compress and expand the earth in the direction of their travel; and 2) S (or shear) waves, which cause motion of the earth in a direction perpendicular to their path. Because a quake's P waves travel through the earth slightly faster than its S waves, they arrive at seismic listening posts ahead of the S waves. While investigating the small tremors that often occur in the Garm region south...
...phenomenon could be used as a predicting tool in other quake-prone areas. Yash Aggarwal, a 30-year-old graduate student of Indian descent at Columbia University's Lamont-Doherty Geological Observatory, did not share the skepticism. As part of his doctoral work, he decided to study the seismic records of the swarms of microquakes that had occurred during 1971 in the Blue Mountain lake region of New York's Adirondack Mountains. Aggarwal's hunch paid off. Writing in Nature, he and his associates report that they also found large and significant changes in the relative velocity...
...older survivors knew from firsthand experience, Managua was disaster-prone. In 1885 and again in 1931, the city was virtually leveled by quakes, with heavy loss of life (some 1,450 died in the 1931 catastrophe). Lying along the "circle of fire," a ring of volcanoes and seismic fault lines that encircles the Pacific from the Aleutians down through the western rim of the Americas to New Zealand and up through Japan, Central America is frequently shaken by geologic turbulence...
MEASURED on a human Richter scale, the Managua earthquake ranks as one of history's more modest seismic upheavals. In 1556 a quake collapsed thousands of cave dwellings in the cliffs of China's Shensi province, killing an estimated 830,000 peasants. In 1755 more than 50,000 died in a series of tremors that destroyed the city of Lisbon and inspired Voltaire to compose his moving Poem on the Lisbon Earthquake...