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~, i t, ~1. Citizen Inc Yests ground motion are higher at short distances, and higher frequency vibrations have been found to be less damaging. Although the Bureau of Mines research which forms much of the basis for the OSMRE regulations has shown that there is a possibility of minor damage at velocities even slightly below 1.0 inch per second, in normal conditions, with properly constructed buildings, damage is unlikely to appear at velocities under 3.0 inches per second. Whenever damage is referred co in this context, it is also necessary to remember that minor, threshold, cosmetic damage is what is meant. (See Chapter 4, page 29.) When major, structural damage, such as the collapse of brickwork, extensive and serious cracking threatening structural integrity, or concrete cracking is found (apazt from the small drying-out or temperature cracks to be found in virtually all concrete) then either the ground motion exceeded 3 or 4 inches per second, or sane other reason exists for the damage. See "CAUSES OF STRUCTURAL DEFECIS" on pages 4 to 6 of this manual. If an operator is in compliance with the regulations, the citizen's house will be effectively protected from damage, even when the blasting vibrations are repeated on a daily basis over a period of yeazs. It is a relatively simple thing to check on whether an operator is in compliance, and that is by measuring - or "monitoring" - the vibrations over a period of time. Marry mitre operators own or rent monitoring instruments, and most will readily accede to a request from a householder to monitor vibrations in this way. Blast vibration consultants, too, will be happy to carry out this service, either in person,' or simply by means of an instrument rental for a short period. Most available instruments are very easy to use, and aze quite impartial: they will accurately report a vibration level regardless of who owns them, or who switches them on! If velocities in excess of the regulatory levels are recorded, then regardless of the method of regulatory compliance that the operator has chosen (See Chapter 9, page 73}, it will be apparent that the operator is in violation of the regulations. This is because the "scaled distance" option is so safe and conservative that it is almost impossible to exceed regulatory vibration levels when it is used. In any case, should this situation arise, subsequent seismic tests would be able to establish this possibility. If the operator is using one of the velocity limitation options, then there would be no question at all. Where airblast is concerned, although this is the effect that causes the most annoyance of all, it is also the effect that causes the least damage. Airblast that can cause even minor damage is so much higher - some 10 to 15 times higher - than [he• marim,em allowed under the OS'2~II2E regulations, that i[ can virtually be discounted as a possible cause of damage. In arty event, whenever airblast does caul damage, it always shows up first as broken window panes. Ig a building suffers structural damage, arrd it does not have arty broken windows, then the cause was other than airblast. 112