NOTES ON EARTHQUAKES.

Otago Daily Times, Issue 13586, 7 May 1906, Page 5

NOTES ON EARTHQUAKES.

A correspondent sends us the following suggestions he culled somo time ago when reading some works on seismology that appear worthy of being borne in mind by the public authorities and private pro-perty-ownors at tho present time, and remarks: "Your facile and sapient writer 'Civis' in his first 'Passing Noto' of Saturday must liavo had similar reflections in his mind." The destruction of buildings produced by earthquakes is not irregular. The earthquakes in Japan in 1891 destroyed between Nagoya and Gifu a scries of villages that had onco formed what was practically a continuous street more than 25 miles in length, and all that remained wero two long lines of debris." Generally speaking, all tlio buildings yielded on the side where, in consequenco of windows and doors, they were tho weakest. The sajne effects wero not.ioed by Darwin in the after-effects of the great earthquake at Concepcion in 1835. Later, in 1879, at Tokio, similar results were noted. Some occurred at Belluno in 1873. Mallet recorded similar damages after tho Neapolitan earthquake of 1857. Tho Imperial College of Engincer-

irig in Tokio ill 1880 conducted a series of observations to sea how these damages could be mitigated "and provided for beforehand. They found I hat buildings designed with cracks and joints between those parts which were likely to have different periods of vibration were more stable than others. Thev also indicated that roofs with a moderate pitch stood better than those with the steepest pitch. Arches and openings in heavy walls, which as a rule are generally strengthened to deal with vertical thrusts, require in earthquake areas to 1m specially mado strong enough to resist horizontal pulls. Long chimneys through roofs should pass freely through without being tied to or coming iu contact with any of the main timbers.

Over rigidity of buildings by firmly joining them together by Ixiits and angle irons is a mistake in places subjcct to seismic shocks. High buildings and heavy overhanging cornices arc dangerous, ill the 1868 earthquake) in Sail Francisco this was especially noted. .Unnecessarily heavy roofs 011 weak frameworks should be avoided. Instead of heavy plaster mouldings for internal decorations use papiermache or embossed zinc ones. In Wellington in 1855 (ho brick buildings on the sides of the hills suffered tnorc than thoso on the flat. At San"-Ifrancisco and Areqnipa in 1868 and at Messina tlio opposite was noted. Experience has shown that buildings with, a basement surrounded by open areas arc less liable to destruction than those rigidly tied to the surface. Sites for heavy buildings should not bo selected in soft ground, slopes, or scarps. The foundations should be deep, and liavo a free' basement; lowest walls should be especially strong and well bonded. But tlio iron or steel bonds must, act uuon largo surfaces and bo interlaced. Reinforced concrete buildings aro strongly believed in for these'areas. Largo water or sewage concrete conduits require to bo of the reinforced type, and the segments, in addition to ther>ordinary spiral and zonal steel or iron ribs, require to be laced togetlier by longitudinal bonding rods, such as aro used in tho -numerous types of reinforced concrolo work. In many parts adobe buildings aro preferred. In most areas that have been subjcct to seismic shocks tho authorities aro very strict in their building regulations to this end. This is especially so in Japan, Manila, and many parts of Italy.

More da-mages have ensued from tho fires which have succeeded earthquake shocks than from the shocks themselves.