kno\vli:dgi:. 



August, 1912. 



the movements witliin it w liicli caused tlie e.-irtlKjuake 

 died out practically before reaching the surface. 



In the absence of crustal deformation, it would be 

 too much to e.xpect that a re-survey of the central 

 districts would show any appreciable change of level, 

 and. if anv could be detected, the district which 

 includes Dehra Dun and Mnssoorie would naturally 

 show less than that which includes Kangra and 

 Dharmsala. Unfortunately it is only for the former 

 district that an\- previously-made line of levels is 

 available. In 1S6J the line from Saharaninir, tlirough 

 Dehra Dun, to Mussoorie was levelled. In 1 904, less 

 than a vear before the earthquake, the portion from 

 Dehra Dun to Mussoorie was repeated, and again a 

 year later, or about a month after the earthquake. 

 The last operation showed that either Dehra Dun 

 had risen about five inches with respect to Mussoorie 

 or that Mussoorie had sunk the same amount with 

 reference to Dehra Dun. There ma\' also have been 

 movements of both places. A fresh series of levels 

 was, therefore, carried out along the whole line from 

 Saharanpur to Mussoorie in the cold weather of 

 1906-7. These corroborated the work of 1905, and 

 proved that Dehra Dun had risen about five inches, 

 that is. regarding the height of Saharanpur as fixed, 

 while the position of Mussoorie was almost un- 

 changed. The amount is a small one, but every 

 precaution to avoid error was taken, and, as the 

 change occurred between May, 1904, and May, 1905, 

 it seems reasonable to conclude that one result of the 

 deep-seated movements which caused the earth- 

 quake was this very slight buckling upwards of the 

 crust. 



The nature of these deep-seated movements is 

 obscured both by the absence of crust-deformations 

 and by the want of precise observations in the central 

 area. They appear, however, to have taken place 

 within two detached regions, one below Kangra and 

 Dharmsala and stretching in an east-south-east 

 direction for fifty miles or more, the other, below 

 Dehra Dun and Mussoorie, of much inferior length. 

 The axes of the two detached isoseismals being 

 roughly parallel, it may be inferred that the foci were 

 also elongated in the same direction, though not in 

 the same line. The total length of the com()lex focus, 

 including the break in the neighbourhood of Simla, 

 must have been about one hundred and fifty miles. 

 Throughout its whole extent the disturbance must 

 have taken place almost simultaneously. Had it 

 been otherwise, two great shocks would have been 

 felt at Dehra Dun, one coming from the focus below, 

 the other from the more important focus near Kangra. 

 There may, however, have been an interval, amount- 

 ing to a considerable fraction of a minute, between 

 the disturbances in the two foci, that in the Dehra 

 Dun focus being precipitated by the increased strain 

 brought into action b\- the movement within thr 

 Kangra focus. 



Though we cannot picture the movements which 

 caused the Kangra earthquake so clearly as in the 

 case of the San Francisco earthquake of the follow- 

 ing Near, the earthquake certainly belongs to the 



great class of tectonic shocks, those which are the 

 result of the moulding operations that still take place 

 within the Earth's crust. The nature of the shock 

 within the greater central area, where it was 

 manifested as a shift rather than as a vibratory 

 movement, points to an actual displacement of the 

 surface-crust, even though no permanent trace of it 

 was left. There can be little doubt that the dis- 

 placement was the last of those movements which 

 culminated in the uplifting and growth of the 

 Himalayas. This great range runs in an even 

 circular arc, with its convexity towards the south. 

 The Kangra earthquake occurred in the part where 

 strong shocks are most frequent in such ranges, 

 nameh'. on the convex steeply-sloping side. 



Mr. Middlemiss points out a remarkable relation 

 between the two foci and the geological structure of 

 the district. The principal features of this structure 

 are rejiresented in the sketch-map (Figure 326). 

 The area indicated by diagonal shading is occupied 

 by the old Himalayan rocks. Bounding it on the 

 south-west is a band, show n bv dotted shading, con- 

 sisting of the \-ounger Tertiary formation of the 

 Sub-Himalaya. To the south-west of this, again, 

 the w hole region is covered with alluvium. Between 

 the Tertiary rocks of the Sub- Himalaya and the 

 older Himalayan formations, there runs a great 

 boundary-fault, which, just to the north of Dharm- 

 sala, bends rather sharply to the east, and, after 

 sweei)ing in a great curve round the foot of the 

 Simla mountain spurs, returns to its normal direc- 

 tion. This direction is maintained until near Mus- 

 soorie, when it again bends to the east, sweeps round 

 in the same way as before, past Dehra Dun, but in a 

 smaller curve, after which it once more resumes its 

 normal direction. " Nowhere else along the Hima- 

 lavan mountain-foot, as we know it," says Mr. 

 Middlemiss, " is there such exceptional irregularity, 

 unevenness one might say, in the disposition of these 

 bordering bands of Tertiary strata." 



Now, as will be seen from Figure 326, the two 

 earthquake centres lie in the Sub-Himalayan band, 

 nearl\- but not quite along the line of the great 

 boundary-fault, and precisely in those parts where 

 the band widens and invades the older Himalayan 

 mass. Moreover, the main centre lies in the larger 

 ba\-, and the secondary centre in the smaller. Mr. 

 Middlemiss further notices that the regions occupied 

 bv the earthquake centres are both " regions of 

 reversed faulting, where a packing of the strata and 

 an overriding of the younger by the older rock series 

 is S[)ecially prominent. They coincide with parts of 

 those regions where there is irregularity in that 

 packing, and where the regular marginal arc of the 

 mountain, as expressed in the parallel earth folds 

 and faults, is interrupted." 



The [)lace of the Kangra earthquake among other 

 destructive shocks is not easy to determine. Loss 

 of life and injury to property are fallacious guides. 

 The one depends on the time at which the shock 

 occurs, the other on the construction of the 

 buildings and the nature of the materials employed. 



