VIEWS OF SCIENTISTS.

Press, Volume LXII, Issue 12483, 20 April 1906, Page 8

VIEWS OF SCIENTISTS.

MR G. HOGBEN, M.A.

A RECURRENCE OF THE SHOCKS PREDICTED. (special to 'thk tress.") WELLINGTON, April 19. Mr G. Hcgbe-n, M.A., a recognised authority on earthquakes, hss an up-to-dare seismograph under his house in Tinakori roa:l. At the time cf writing lie ha,* not developed the records taken ye-torday, but no doubt the 'Frisco <ar:hqt:akc will be duly recorded on the {,':;;>: ographic tap?, which works automatically. Strangely enough, th-o in«t.nini!>uit recorded a ssvere earthquake in fccnie part of tho ivcr'ld some time ;igo of which no mention, was iuadi> in the r.ow,.»pjpr-n<. Regarding earthquakes generally. Mr Hc-2,'li:'ii said they were only 'r-ymptoms of rncveim ins that were' going en below the earth's surface. If the niov:>n>?nt* wt-nt on gradually, there won 1:1 be no appreciable manifestatic:i cf the change on tho surface, but if. on the other 'hand, tho movemente wc;o rapid and irregular, earthquakes would occur. It va.s important to remember about earthquakes that their origin lay in from five to twenty-five miks b.-low the earth's surface ; that the reeks in whinii the orighiis were situated wero very rigid, and far more highly clastic than, air C" string: and that the effects cl'-tMTed in eharp or eovero earthquakes (wliLt'hcr th?y were the disturbance oi" more or kv.s inoveable objects upaiii tho earlih's surface, or cf part of that surface itself) were really generally (secondary effects. Two important oaus?s cf earthquakes wero the gradual cooling of the earth iind thi> loading of tho ocean bnd through denudation of the land surface. In explanation cf tho second cause. Mr Hegbcn t=.a-i:l the rivers brought down cnonnciis masses of material, which wero deposited in the cecan bed*. The land surface pressure. w;ts accordingly reduced, and the enormously increased pressure on tho wa teds caused internal movements, which ultimately resulted in fractures, and caused what we call earthquakes. , A line of weakness mns right through California, but San Francisco is not the woriit city in the country so far as oaiithquakrs arc concerned. It lies in a isi'ivnnic, but not in a volcanic, district. Tho earthquakes in San Francisco, Mr Hcgben thought, were due to readjustments of the earth's crust be-low I'he R'Cckies and parallel ranges, including tin? ranges in. the ocean bed to the west. They belonged to the same system as those in Mexico , . Mr HcHghoii does not- believe that volcanoes niul eartluiuaketi are due to the .same cause. They'wore quite distinct. Where, a volcanic eruption took place, tlip.ro were, of course, earthquakes, lv.it they wero purely lccal. In the seismic region on which San Francisco is situated, -lie said,, it was evident big adjustments were going en, and there would alnvcMt certainly be recurring shocks. Wlhere there were l*g mountain range*, earthquakes would occur. In Japan »nd the- Himalayae, for instance, disturbances wero, and would be, frequent.