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A simplified tectonic map of Nepal and its adjoining regions, Central Himalaya (modified after Dasgupta et al. 1987)
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Time dependent seismicity investigation in six seismogenic sources of Nepal and its adjoining areas in the Central Himalaya reveal that there is intermediate time clustering of the moderate size shallow earthquake in each seismogenic source. The inter-event times, between the successive shallow mainshocks, of the magnitude equal to or larger than c...
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... geological as well as tectonic investigations in Himalayas. More recent works on the geology and structural framework proposed for Nepal Himalaya are presented by Upreti (1999), for central Himalaya by Avouac (2003) and for the entire Himalayan region by Hodges (2000) and Yin (2006). A simplified tectonic map of the study region is shown in Fig. ...
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Citations
... Repeat times of strong and large earthquakes have been widely used by various researchers for long-term earthquake prediction in recent years (Gardner and Knopoff 1974, Shimazaki and Nakata 1980, Koyama et al. 1995, Papazachos et al. 1997b, Kagan 1997, Karakaisis 2000, Stein 2002, King and Bowman 2003, Mulargia and Geller 2003, Parsons 2004, Kerr 2004, Helmstetter and Sornette 2004, Corral 2004, Weldon et al. 2005, Paudyal et al. 2009, Nekrasova et al. 2010, Panthi et al. 2011). In order to characterize repeat times of great earthquakes, the conditional recurrence time and magnitude distributions for worldwide seismicity during stationary periods were determined. ...
... The earthquake recurrence intervals are the time interval between the largest mainshocks occurred in earthquake prone region. A regional time-and magnitude-predictable model has been proposed by Papazachos and Papaioannou (1993) and applied successfully in different seismically active regions to estimate the magnitude and the time of occurrence of forthcoming earthquakes (Papazachos et al. 1997a, b, Karakaisis 2000, Qin et al. 2001, Sayil 2005, Paudyal et al. 2009, Yadav et al. 2010, Shanker et al. 2012). According to this model, the time of occurrence of the next mainshock in a certain seismogenic region is positively dependent on the magnitude of the last mainshock in this source. ...
In order to estimate the recurrence intervals for large earthquakes that occurred in the Marmara region, this region, limited with the coordinates of 39°–42°N, 25°–32°E, has been separated into seven seismogenic sources on the basis of certain seismological criteria, and regional time- and magnitude-predictable model has been applied for these sources. Considering the interevent time between successive mainshocks, the following two predictive relations were computed: log T
t = 0.26 M
min + 0.06 M
p–0.56 log M
0 + 13.79 and M
f = 0.63 M
min − 0.07 M
p + 0.43 log M
0 − 7.56. Multiple correlation coefficient and standard deviation have been computed as 0.53 and 0.35 for the first relation and 0.66 and 0.39 for the second relation, respectively. On the basis of these relations and using the occurrence time and magnitude of the last mainshocks in each seismogenic source, the probabilities of occurrence P(Δt) of the next mainshocks during the next five decades and the magnitude of the expected mainshocks were determined.
... This is called the ''time-and magnitudepredictable model.'' This model has been also tested successfully in several parts of the continental fracture system: central America (Papadimitriou 1993; Panagiotopoulos 1995), Greece and Japan (Papazachos 1989; Papazachos and Papaioannou 1993; Karakaisis 1994 Karakaisis , 2000 Papazachos et al. 1994a), Alpine-Himalayan belt (Papazachos et al. 1994bPapazachos et al. , 1997b Paudyal et al. 2009), Circum Pacific belt (Papazachos et al. 1994b; Papazachos et al. 1997a; Papadimitriou et al. 2001), Eastern Anatolia (Karakaisis 1994; Sayil 2005); Northeast Himalaya (Shanker and Singh 1996; Shanker and Papadimitriou 2004; Yadav et al. 2010; Panthi et al. 2011; Shanker et al. 2012). One of the most seismically active regions in the world is the Alpine-Himalayan Belt which extends from the Azores to Indonesia. ...
Instrumental and historical data on mainshocks for 13 seismogenic sources in western Anatolia have been used to apply a regional time- and magnitude-predictable model. Considering the interevent time between successive mainshocks, the following two predictive relations were computed: log T
t = 0.13 M
min + 0.21 M
p − 0.15 log M
0 + 2.93 and M
f = 0.87 M
min − 0.06 M
p + 0.33 log M
0 − 6.54. Multiple correlation coefficient and standard deviation have been computed as 0.50 and 0.29, respectively, for the first relation, and 0.65 and 0.47, respectively, for the second relation. The positive dependence of T
t on M
p and the negative dependence of M
f on M
p indicate the validity of time- and magnitude-predictable model on the area considered in this study. On the basis of these relations and using the occurrence time and magnitude of the last main shocks in each seismogenic source, the probabilities of occurrence P(Δt) of the next main shocks during the next 50 years with decade interval as well as the magnitude of the expected main shocks were determined. The highest probabilities P
10 = 80 % (M
f = 6.8 and T
t = 13 years) and P
10 = 32 % (M
f = 7.6 and T
t = 29 years) were estimated for the seismogenic source 11 (Golhisar-Dalaman-Rhodes) for the occurrence of a strong and a large earthquake during the future decade, respectively.
... After long debates and discussions a Regional Time-and Magnitude-Predictable Seismicity Model have been accepted and applied successfully in different seismically active regions to estimate the magnitude and the time of occurrence of forthcoming earthquakes. These models have put forward to Central Himalaya and its vicinity (Paudyal et al., 2009); Eastern Anatolia (Sayil, 2005); Taiwan ( Wang, 2005); Hindukush Pamir Himalaya ( Shanker and Papadimitriou, 2004); China (Qin et al., 2001); Circum-Pacific belt ( Papadimitriou et al., 2001); Greece and Japan (Karakaisis, 2000); Alpine-Himalayan belt (Pa-pazochos et al., 1997); North-east India (Shanker and Singh, 1996); Indonesian region ( Papadimitriou and Papazachos, 1994); the Aegean area (Papazachos and Papaioannou, 1993); New Guinea-Bismark sea region (Karakaisis,1993); the Western coast of the South and the Central America (Papadimitriou, 1993); Greece (Papazachos, 1989); NorthEast India Himalaya (Panthi et al., 2011) and others. Applicability of the Time-and Magnitude Predictable model has been tested in northeast India Himalaya and its adjoining regions bounded by 20°-32° N and 88°-98° E, and finally evaluate the seismic hazards in the identified seismogenic sources. ...
Northeast Himalaya and its adjoining region India, has been delineated into nineteen seismogenic sources on the basis of certain seismological and criteria for the estimation of repeat times of earthquakes, to apply a regional time-and magnitude-predictable model for all these sources to study the future seismic hazard. For this, published earthquake data since 1906 to 2008 from different available earthquake catalogues and books have been used. Considering the inter-event time between successive mainshocks, the following two predictive relations were computed: logT t = 0.01 M min + 0.22 M p -0.05 log m 0 + 0.98 and M f = 0.89 M min – 0.26 M p + 0.29 log m 0 -5. Multiple correlation coefficient and standard deviation have been calculated as 0.50 and 0.26, respectively for the first relation and 0.75 and 0.41, respectively for the second relation. The positive dependence of T t on M p indicates the validity of time predictable model on the area considered in this study.on the basis of these relations and using the magnitude and time of occurrence of the last mainshocks in each seismogenic source, time dependent conditional probabilities of the next mainshocks and their occurrence during the next 10, 20 and 30 years as well as the magnitude of the expected main shocks are forecast.
... Several authors (Evison, 1977;Mogi, 1977;Kanamori, 1981;Singh and Singh, 1984;Ohtake et al., 1977;Gupta and Singh, 1989;Shanker et al., 1995Shanker et al., , 2010Singh et al., 2005;Paudyal et al., 2009) have have suggested that seismicity preceding major earthquakes could be defined by the following episodes: (1) background/normal seismicity, (2) precursory swarm, (3) quiescence, (4) foreshocks and (5) mainshock. In most of the anomalous sequences, the magnitude of mainshocks observed to be 1-2 units higher than the magnitude of the largest swarm event (Evison, 1977;Singh et al., 1982Singh et al., , 2005Shanker et al., 1995). ...
This paper reports that three earthquake sequence occurred in 1996 (mb 5.9), 1998 (mb 5.8) and 2004-2005 (mb 6.2, 6.3) were observed preceding the anomalous seismic activity. The nature of anomalous seismicity associated with these earthquakes have been investigated considering earthquakes with mb≥4.1 (cut off magnitude for this region) in four seismic episodes (NAGM): normal/background (N); anomalous/swarm (A); precursory gap (G) and mainshock sequence (M), respectively. It is established here that the anomalous seismicity/swarm patterns follow episodes of relatively very low seismic activity and it is an important finding to visualize that an area might be preparing for the occurrence of a forthcoming mainshock. Such anomalous seismic patterns were observed prior to medium size mainshocks that occurred from 1963 to 2006 in South Central Tibet (SCT) region to the north of Central Himalaya. From these observations it may be inferred here that the patterns of anomalous seismicity/earthquake swarms may be considered as an important parameter (precursor) for the forecasting of long-range earthquake hazards in the SCT region. In consideration of spatial and the temporal clustering of swarm events that are prominent and confined in a vertical column of 10-45km, enabled to locate potential area enclosed by 29.6-30.1°N and 87.8-88.1°E where future earthquake of magnitude 6.0 and above in the depth range 25±15km may be seated. In view of this multi-parameter short term precursory signals monitoring is suggested for the delineated preparatory area to make earthquake prediction/forecasting programs more meaningful.
... The same region of the Western Nepal was also considered as one of the seismogenic sources in which probability is estimated to be as 85% for the next 10 years from 2005 for an earthquake with magnitude 6.4 0.2 using the time and magnitude predictable model (Paudyal et al., 2009). It is worth to mention that the estimates of time and magnitude associated with the impending earthquake using two different methods, namely the anomalous seismic activity and the time-magnitude predictable model are in good agreement with each other. ...
An extremely complex geotectonic framework coupled with high seismic status has made the Central part of the Himalayas, a destination to study the complex inter-continental collision processes. The collision also caused large scale deformation and high seismicity of vast region of colliding continents. This region displays all major tectonic features of the Himalayan mobile belt and is seismically one of the active regions in the Himalayan arc. Focal mechanism solutions bear out a multifaceted pattern. Thrust environment is dominant in the Western and Central Nepal region, whereas, in the Eastern Nepal, it is a amalgamation of thrust and strike-slip with large thrust mechanism. In western region thrust faulting coupled with shallow dip nodal planes reflects the Indian lithosphere is under-thrusting at a shallow angle. Here, the crustal shortening in north- south direction in which earthquakes is generated due to northward compression. The shortening was accommo-dated by development of various NW-SE trending structures like Himalayan Arc MCT (Main Central Thrust), MBT (Main Boundary Thrust); MFT (Main Frontal Thrust). The observed change in the faulting pattern in the eastern parts of the thrust zone may indicate substantial movement along the transverse faults, as compared to that of the western region with the changes in the deep crustal structure. The thrusting decreases rapidly with increasing focal depth and deformation occur due to strike-slip motion at greater depths. This may investigative of an unstable state of the upper mantle leading to a rapid deformation in the presence of high degree of thermal regime. The composite stereographic projection of the compression and tension axes suggest a shallow compressive stress, dipping N-S to NE-SW in Western Nepal whereas it is N-S to NNE-SSW direction of compression at a shallow angle in Eastern Nepal. The region produced a number of devastating events in the past. Central Himalaya comprising Nepal and its adjoining region in which different types of faulting patterns exist have signatures of a great earthquake in 1934 and a number of large events thereafter, advocate serious seismic hazard in the region.
Keywords: Fault-Plane Solution, Collision Processes, Stress Pattern, Nepal Himalaya, Stereographic Projection
... The same region of the Western Nepal was also considered as one of the seismogenic sources in which probability is estimated to be as 85% for the next 10 years from 2005 for an earthquake with magnitude 6.4 0.2 using the time and magnitude predictable model (Paudyal et al., 2009). It is worth to mention that the estimates of time and magnitude associated with the impending earthquake using two different methods, namely the anomalous seismic activity and the time-magnitude predictable model are in good agreement with each other. ...
... The same region of the Western Nepal was also considered as one of the seismogenic sources in which probability is estimated to be as 85% for the next 10 years from 2005 for an earthquake with magnitude 6.4 0.2 using the time and magnitude predictable model (Paudyal et al., 2009). It is worth to mention that the estimates of time and magnitude associated with the impending earthquake using two different methods, namely the anomalous seismic activity and the time-magnitude predictable model are in good agreement with each other. ...
... The same region of the Western Nepal was also considered as one of the seismogenic sources in which probability is estimated to be as 85% for the next 10 years from 2005 for an earthquake with magnitude 6.4 0.2 using the time and magnitude predictable model (Paudyal et al., 2009). It is worth to mention that the estimates of time and magnitude associated with the impending earthquake using two different methods, namely the anomalous seismic activity and the time-magnitude predictable model are in good agreement with each other. ...
It is not only the basic understanding of the phenomenon of earthquake, its resistance offered by the designed structure, but the understanding of the socio-economic factors, engineering properties of the indigenous materials, local skill and technology transfer models are also of vital importance. It is important that the engineering aspects of mitigation should be made a part of public policy documents. Earthquakes, therefore, are and were thought of as one of the worst enemies of mankind. Due to the very nature of release of energy, damage is evident which, however, will not culminate in a disaster unless it strikes a populated area. The word mitigation may be defined as the reduction in severity of something. The Earthquake disaster mitigation, therefore, implies that such measures may be taken which help reduce severity of damage caused by earthquake to life, property and environment. While ``earthquake disaster mitigation'' usually refers primarily to interventions to strengthen the built environment, and ``earthquake protection'' is now considered to include human, social and administrative aspects of reducing earthquake effects. It should, however, be noted that reduction of earthquake hazards through prediction is considered to be the one of the effective measures, and much effort is spent on prediction strategies. While earthquake prediction does not guarantee safety and even if predicted correctly the damage to life and property on such a large scale warrants the use of other aspects of mitigation. While earthquake prediction may be of some help, mitigation remains the main focus of attention of the civil society. Present study suggests that anomalous seismic activity/ earthquake swarm existed prior to the medium size earthquakes in the Nepal Himalaya. The mainshocks were preceded by the quiescence period which is an indication for the occurrence of future seismic activity. In all the cases, the identified episodes of anomalous seismic activity were characterized by an extremely high annual earthquake frequency as compared to the preceding normal and the following gap episodes, and is the characteristics of the events in such an episode is causally related with the magnitude and the time of occurrence of the forthcoming earthquake. It is observed here that for the shorter duration of the preparatory time period, there will be the smaller mainshock, and vice-versa. The Western Nepal and the adjoining Tibet region are potential for the future medium size earthquakes. Accordingly, it has been estimated here that an earthquake with M 6.5 ± 0.5 may occur at any time from now onwards till December 2011 in the Western Nepal within an area bounded by 29.3°-30.5° N and 81.2°-81.9° E, in the focal depth range 10 -30 km.
... GUPTA and SINGH (1986) invoked similar considerations to estimate the probable time of occurrence of the 6 August, 1988 earthquake in Arakan Yoma. The same region of western Nepal was one of the seismogenic sources in which the probability is estimated to be 85% for the 10 years starting in 2005 for an earthquake with magnitude 6.4 ± 0.2 using the time and magnitude predictable model (PAUDYAL et al., 2008b). It is noted that the estimates of time and magnitude associated with the impending earthquake using two different methods, namely the anomalous seismic activity and the time-magnitude predictable model, are in good agreement with each other. ...
Precursory swarms associated with major earthquakes in the Western Nepal Himalaya and its adjoining region (bounded by 28.0°–31.0°N and 79.5°–82.2°E) have been studied using seismicity data from 1963 to 2006. The delineation of preparation zones for future seismic disturbances is carried out using the temporal and the spatial distribution of earthquakes, considering the events with cutoff magnitude m
b ≥ 4.3 in four anomalous episodes: normal/background (N); anomalous/swarm (A); precursory gap (G) and main shock sequence (M), respectively. Five cases of anomalous seismicity have been identified, including two cases for which quiescence episodes still continue. Three moderate earthquakes of 1980 (m
b 6.1, Bajhang), 1984 (m
b 5.6, Bajura) and 1999 (m
b 6.6, Chamoli) in Western Nepal and its adjoining Indian region were preceded by well-defined patterns of anomalous seismicity/precursory swarm. Two additional cases of anomalous seismicity patterns were observed: (1) 1999–2006, and (2) 2003–2006. In these two cases no main shock has yet occurred. However, the seismicity from 1999 onwards has fluctuated from low to high to low, as in the precursory sequences for previous earthquakes. The occurrence of the swarm sequence followed by a quiescence phase, which is still continuing, is an indication of a precursory seismicity gap in the region. From the predictive equations developed for the Himalayan frontal arc, it is estimated that an earthquake of M 6.5 ± 0.5 may occur at any time up to 2011 in an area bounded by 29.3°–30.5°N and 81.2°–81.9°E, in the focal depth range 10–30 km.
