**3. Results and discussion**

The focused study areas both are tectonically active in nature, and there is no previous research conducted in the two earthquake-stricken areas considering lineament change. This research has been tried to test using Landsat 8 OLI dataset for the first time based on the newly developed theoretical model. To quantitatively evaluate the present methods, lineaments were automatically extracted from each image after principal component analysis (PCA). Epicenter-based single tile images were considered to observe the changes of the lineaments related to both the earthquakes.

The following sections (3.1–3.4) represent the present research derived results, based on three different situations. First, results highlight automatic extraction of lineaments data along with lineament length information; second, temporal data-based lineament fluctuations observed by applying vector overlay technique of ArcGIS 10.5 software, and third, rose diagram was created to know the directional changes. Finally, the overall integrated assessment and statistical information-based lineament change comparison were performed for the two impending earthquakes. The present significant contribution of the lineament data suggests that data have potential enough to detect pre-earthquake anomaly in advance without having integration of processed satellite imageries, geological map and field validation data.

> absence of earthquake, where only 11,080 lineaments observed (85 days before) (**Table 2**), whereas the number of lineaments was found decreasing (25,917) in post-earthquake phase (12 days after the earthquake) probably due to the release of strain and structural damage done by the high magnitude earthquake (7.8 Mw), compared to its three-preceding anomaly phases. The real cause is unclear till now regarding why the change was occurred prior to earthquake strike. However, simple explanations have been given only based on the experi-

> Brackets terminology in the 1st column refers lineament anomaly-no, means normal behavior of lineaments and anomaly-yes, means abnormal behavior of lineaments and in the 2nd column b refers before and a refers after earthquake

(earthquake occurrence date: 4 January 2016). Source: data extracted using PCI Geomatica-9.1, ArcGIS 10.5.

**Table 3.** Statistical information of the extracted lineament of Imphal, Manipur and its surrounds, Eastern India.

**Length (km)-min**

19 March 2015 (anomaly-no) 292 (b) 14,524 0.015 5.031 0.326 4734.38 0.184 30 Nov 2015 (anomaly-yes) 36 (b) 34,018 0.030 31.411 0.676 23014.35 0.750 16 December 2015 (anomaly-yes) 20 (b) 29,358 0.030 31.398 0.670 19678.25 0.658 1 January 2016 (anomaly-yes) 4 (b) 42,840 0.030 31.423 0.688 29462.89 0.674 17 January 2016 (anomaly-yes) 13 (a) 62,332 0.030 31.404 0.673 41938.37 0.558

**Length (km)-max**

Pre-earthquake Anomaly Detection and Assessment through Lineament Changes Observation…

**Mean value (km)** **Sum value (km)**

http://dx.doi.org/10.5772/intechopen.72735

**SD value (***σ***)**

159

The lineament changes and anomalous behavior also observed through line length statistics (**Table 2**). Total line length was observed 18025.26 km, the minimum and maximum values were found quite low and the SD value was observed the highest in the absence of earthquake event. The anomaly phases were observed in the presence of earthquake event, where the maximum length and the SD value were found almost similar in 36, 20 days before earthquake (20 March and 5 April 2015), but not similar in 4 days before earthquake (21 April 2015). The mean length was dropped 0.043 km along with the maximum and SD length of lineament (in km) was sharply decreased (**Table 2**), representing high abnormal behavior (strong anomaly) prior to earthquake event. The same variables of lineament were found increased after the earthquake event (12 days later), as high magnitude of earthquake already ruptured in this region. There was a tendency of lineament to return to its original status but failed

On the other hand, similar method applied over Imphal, Manipur (6.7 Mw) earthquake assessment. The total number of lineaments observed 14,524 in number (**Table 3**), representing "no anomaly" in the absence of earthquake event (292 days before). However, the lineament distribution during 30 November 2015 to 17 January 2016 represents the abnormal behavior. The number of lineaments was sharply decreased (4660) from initial to middle phase (30 November 2015 to 16 December 2015). The total number of lineaments found the highest in number (62,332) than its all four preceding values, observed in the post-earthquake stage (**Table 3**).

As mentioned in Section 2.3.2 under Section 2.3 (on methodology), lineament fluctuations changes were observed based on temporal data. **Figures 5(a**–**g)** and **6(a**–**g)** represent temporal lineament fluctuations over Gorkha of Nepal and Imphal of Manipur regions, respectively.

**3.2. Lineament fluctuations observation through overlay analysis**

mental output from the extracted lineament results.

**Date of image acquisition Days** 

**(b/a)**

**No. of lineament**

completely to return to its initial situation.
