« PreviousContinue »
In addition to the above meteorological observers' reports, the Director of the Geological Survey of India has received from the
Deputy Commissioner, Rawalpindi, valuDetailed reports from able tabular statement embodying the Rawalpindi district.
reports of 53 observers in different tahsils of the Rawalpindi district. The duration of the shock is variously estimated from 300 to 3 seconds, the average of all estimates being just under 90 seconds. The greatest number of shocks observed was eight.
ANALYSIS OF OBSERVERS' REPORTS. The isoseismal lines given in the sketch-map forming Fig. 1 have been drawn from the details given in the foregoing meteoro
logical observers' reports, due account Isoseismal lines.
being taken also of the newspaper reports. They show the intensity of the shock according to the modified Mercalli intensity scale (Heck, 1936, pp. 55-56).
FIG. 1.-Sketch-map of north-western India showing the isoseismal lines (modified Mercalli scale) of the earthquake shock of the 14th November, 1937—
A.-Epicentre calculated by Bombay Meteorologist, if earthquake was deepseated.
The observers' reports indicate that the epicentral region of the shock of the 14th November, 1937, is in the Hindu Kush mountains
in Chitral. On account of the Intensity VIII.
absence of reports from this region, one cannot state whether or not the shock attained a greater intensity than VIII in the mountainous regions north-west of Drosh.1 The shape of the isoseismal lines, however, would seem to indicate that the epicentral region was not very large and that it is possible that the maximum intensity of the shock above the focus did not exceed intensity X.
Two reports were actually received from Drosh. One merely stated that the walls of the Telegraph building were cracked and that no details were to hand from outside. The other stated that buildings fell down and that a ground fissure occurred. The newspaper reports indicate considerable loss of property there.
A rumbling noise was heard during the shock by one observer.
It is not possible to separate intensities VII and VI. In this region, the earthquake was accompanied at Gilgit by 'an aeroplane
sound.' The river bank slipped at several Intensity VII-VI.
places and rocks fell from the mountain-side in two localities. It looked like a dust storm all along the river and mountain where slipping occurred.' A 'whisking' sound was heard at Gurais and the walls of the fort cracked and all chimney-tops were dismantled. No sound was heard in Peshawar, but the verandah on the third floor of a new building in the Cantonment collapsed. Older bungalows had moderate falls of plaster. A few buildings were cracked and big stones fell down from the hills near the hill station of Cherat and blocked the roads. There was considerable damage to the tops of big buildings at Rawalpindi; also pakka huts were affected. Sounds were not generally heard accompanying the shock but in various parts of the Rawalpindi district, the noise was compared to was compared to autumnal winds,
autumnal winds,' 'speeding train,' 'thundering,' rolling stones' and 'a washing sound.' In interpreting newspaper reports from Rawalpindi, due consideration must be given to the prevalent style of buildings.
1 The modified Mercalli scale has a maximum intensity of XII, when total damage occurs. In intensity VIII, damage is slight in specially designed (brick) buildings; considerable in ordinary substantial buildings with partial collapse ; great in poorly built structures.
The report from Sonamarg stated that the noise before and after the shocks resembled that made by the start and closing
down of a rice mill. The report from SriIntensity V.
nagar compared the noise to the cracking of walnuts by the fist.' Two boys fell down from windows at Srinagar and received injuries. It would seem that the intensity of the shock at Lahore was just between V and IV.
The following details of the shock of the 14th November, 1937,
were kindly supplied by Dr. K. R. Ramanathan, Bombay.
Meteorologist, Bombay, who also enclosed contact copy of the record of the N.-S. component of the Milne-Shaw seismograph obtained at Colaba :
The Bombay Meteorologist stated that the time of origin deduced from the data of Agra, Bombay and Calcutta and Jeffrey's normal table of travel times is 16 h. 28 m. 10 s. and the position of the epicentre 36.5° N., 72.5° E.
He added that the Bombay seismograms show evidence that the earthquake was a deep focus one with a depth of focus of about 200 km. (SP-P being 1 m. O s.). If this depth of focus be assumed, the position of the epicentre will be shifted towards the north by about a degree. To come to a definite decision on this point, data from other stations and, preferably, also some original seismograms, should be examined.
Dr. S. K. Pramanik, Meteorologist, Calcutta, kindly supplied
the following details of the E.-W. component Calcutta.
of the Omori-Ewing
the Alipore Observatory, Calcutta, as recorded on the 14th November, 1937:
He noted that the intensity was great with maximum movement ‘in secondary'. The shock was of deep focus and the focal depth according to the Brunner chart was 240 km. The epicentral region was possibly at about 37.5° N., 71.5° E.
GENERAL DISCUSSION. The instability of the region between the north-west Hima
layas and the Hindu Kush is well known. Instability of Hindu
In his classic work on the seismic phenoKush well-known.
mena of British India, Montessus de Ballore states (1904, p. 155) =
“A single, but disastrous earthquake is known in Badaksban, northwards of the Hindu Kush, and this renders a great instability probable. Of Chitral nothing is recorded.”
He also states (pp. 157-158) :
“Kashmir is certainly the most unstable district of the region (North-West Himalayas). Earthquakes are both disastrous and numerous there. There are plenty of general causes explanatory of this instability in the geology of the country. The Himalayan fold is deflected there and spreads out in front of the Karakoram massif, so that summits of upper palæozoic and mesozoic formations tower over the depression of Kashmir, about 100 kilometres in length, the direction of which is nearly 8. E.-N. W. The folding has reached a great amplitude there and the