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Pagel~Two • Janut,ry 12, 1981 SadlE~r House instx-umentational scales such as the Richter scale or to determine the intensity of an earthquake when no instrumenta- tionail records are available. A Mercali IV earthquake is roughly equi~~alent to a Richter 3.0 to 3.5 earthquake. A Mercali IV earthquake would be expected to generate ground accelerations between 50 mm/sec./sec, to 100 mm/sec./sec „ or 0.005 to 0.01 time,S the acceleration of gravity. The effect of construction equipment operating upon a1lu~vium is to induce ground vibrations which are similar to the Seismic waves produced by an earthquake. The ground waves vary in amplitude and wave length and travel through the ground strata. The principle difference in this situation is that an earthquake Lasts only a few seconds whereas the ground vibrations caus~sd by construction equipment last for hours each day of operation. The approximate woight of the house including contents is estimated to be 46000 lbs. The force due to ground vibrations ( acceleration x weight gravity acceleration ) is calculated to bs 210 lbs. to 420 lbs. This force generally is a horizontal, cyclical force. The cycle probably varies in length of time ( fractions of a second ). The long term repietitive occilating force caused by low ground accelerations is capable of causing damage to a house. Such damage would initially occur to walla, windows, loose appendages, etc. If the forces occur over a long period of time, the vibrations could cause fatigue stress of failures to connections, concrete and masonry. If the underlying alluvium is not at its .optimum .density, settlement could occur which would induce further damage. _ Cracks occur in buildings because of many reasons. They usually occur within the first 5 years if they occur at a11. Unusual circumstances such as atypical weather or changing environmental conditions can curie cracks at a later age of the structure. CONCLUSIONi If there were no cracks prior to the equipment operation to t:he west of the house,then the damage to the house, manifested by numerous cracks, most likely occured because of the vibrations and vibrational forces induced by the construction equipment. If t:he'cracks were covered up by previous owners, then ground vibrations would be a possible, if not probable, cause of their reoF~ening. At the present time, the inte;,rity of the house is not impaired. However, additional ground vibrations which approximate the intensities described earlier in this report could cause additional damage such as+ (1) more cracks; (2) looe;ening of wind ow s, doors and cabinets; (3) cracking of the