GEOLOGIST’S REPORT

Hokitika Guardian, 28 September 1932, Page 6

GEOLOGIST’S REPORT

CAUSE OF EARTHQUAKE. WELLINGTON, September 27. According to Dr J. Henderson, Director', of the Geological Survey, the recent serious earthquake at Wairoa and Gisborne on the east coast indicates that the great nofih-rioffh-east-s Diking, earth fold which stretches ..ircugli flic whole of the Soutll Island the eastern part of the North Island, and some 1(500: miles across the floor of the Pacific .Ocean, is still'growing. The last earthquake and the foreshocks on the preceding day seem 40 lie definitely connected, he thinks with the Raukudmara section of the fold. “The relieving of the stresses in the . Hawke’s Bay region,” he said, Oprobably increased the pressure in the adjacent area to, the north; hence the present adjustments. Dr Adams’ preliminary determinations place the initial movement out to se£\ off Waipiro, or Open , Bay, but the earthquake was most violent about Gisborne and Wairoa. .This suggests that the movement extended south along a fracture::c,ie and at greatest CO to SO miles south of? Waipiro Bay. Possibly, ox course, the shock from near Waipiro caused an unstable block in the Hawke’s Bay area to move. “Probably the principal movement has now , taken place, but the equilibrium of the whole system, of earth blocks lias been disturbed, and aftershocks, produced by,, minor adjustments, will continue for months. The mapping of the epicentres of. these m/y give some indication of the course of the faults on the sea-floor or on ‘the land. “As is usual, the gieatest material damage seems to have been to buildings erected on alluvium near riverchannels. Wherever such ground is j unsupported, standing at the angle of | repose for the material and the existing conditions, earthquakes open fissures and bring about slumps.”