Strong historical earthquakes around Osh city, Kyrgyzstan

. This paper presents data on strong earthquakes that occurred in the area around Osh city from various literature sources. The information on strong earthquakes of the past has been compiled on the basis of historical data. The catalog of strong earthquakes is given in the radius of 60 km from Osh city. A description of macroseismic data of these earthquakes is given.


Introduction
The survey area is located in the south of Kyrgyzstan, within the south-eastern part of the vast Fergana Valley, in the lower reaches of the Ak-Bura River.It is limited to a radius of 60 km around Osh city, the centre of Osh region in the Kyrgyz Republic, is shown in Figure 1.Information on strong earthquakes of the past has been collected from historical data [1-14 and 16] and from the seismic catalog of the Institute of Seismology of the National Academy of Sciences of the Kyrgyz Republic.The catalog of the strongest earthquakes that have occurred during historical time on the studied territory is given in Table 1 and Figure 1.The analysis of isoseism of strong historical earthquakes shows that the territory of Osh city was affected by earthquakes that occurred within a radius of 60 km, so this paper describes strong earthquakes within this area.Many works are devoted to the tectonic features of this area, but more detailed results are given in the publications [14 and 15]. Figure 2 shows a map of the strong earthquake epicenters and the location of tectonic faults.

Data analysis
Below in chronological order is given a brief description of destructions in the strong record and earthquakes in Osh city and nearby areas caused by these earthquakes.
On November 14, 1883 the earthquake has taken place with magnitude of 7-8 (± 0,5) degrees, the epicenter of which was located in the north at the distance of 7,5 km from the centre of Osh city.Local residents felt an earthquake rumble before the earthquake.The seismic event resulted in human casualties and destruction of residential buildings [1, 3, 4, 6, 9, 11 and 13].
On November 18, 1883, the earthquake has taken place with magnitude of 7 (±0.5)degrees, in the vicinity of Osh city (to the north, about 7.5 km from the centre of Osh city).Residential buildings were destroyed and there were human casualties [6].
On December 18, 1895, the earthquake has taken place with magnitude of 6-7 (±2) degrees with no information from the epicentral zone.The epicenter was on the southern side, about 61 km from Osh city [8 and 9].
About 52 km north-west of Osh was the epicenter of one of the strongest earthquakes in Central Asia -9 (±0.5) degrees of Andijan earthquake which occurred on December 16, 1902.As a result of this earthquake, Andijan city and many settlements located in the epicentral area were almost destroyed.A total of 4,562 people died, 26,000 buildings were destroyed and 7,000 cattle were lost.Changes in the soil were observed during the earthquake: many cracks up to 10 cm wide were formed in Andijan and its vicinity, fountains of sand up to 1 m high were observed in some places, and sinking of the soil layer along the cracks to a depth of up to 70 cm took place.In Andijan city, railroad rails were bent for 4 km.A steam locomotive and wagons of a train preparing to depart from Andijan railway station were breakdown.In Osh city, the earthquake had a magnitude of 6-7 degrees.There were small damages and cracks in adobe buildings [1, 9 and 16].On March 28, 1903, an 8 (±0.5) degrees Aim earthquake has taken place, destroying 11,000 houses and causing human casualties in nearby villages.It was in Andijan, Jalal-Abad, Bazar-Kurgan and Massakh cities with 6-8 degrees.The epicenter of the earthquake was about 31 km north of Osh city.In Osh city, its intensity reached about 6 degrees, which caused cracks in adobe buildings and slight damage [6, 9 and 13].
Four days later, on September 19, 1907, an earthquake (aftershock or separate earthquake) with intensity equal to the main shock -7-8 (±1) degrees occurred.The epicenter was in the same epicentral zone as the previous earthquake, in Osh city and its intensity reached about 6 degrees [9].
On October 18, 1914, in the northeast, about 32 km from Osh city, in the vicinity of Dostuk village, an earthquake of magnitude of 6 (±0.5) degrees occurred [2, 9 and 12].No information is available on the consequences of the earthquake.
Two Kurshab earthquakes occurred on July 6, 1924 with magnitude of 7-8 (±1) degrees and on July 12, 1924 with magnitude of 8-9 (±0.5) degrees.Their epicenters were located 20~25 km northeast of Osh city.The greatest devastation happened in the settlement of Kurshab, which was turned into a pile of ruins within a few minutes; 1073 buildings were destroyed and damaged, the number of victims and wounded was 26.The frame buildings were more resilient, although they sustained considerable damage.Constructions stretching from south to north survived better than those stretching from east to west.An unusual fact is that houses built on a dry site collapsed more than those built on a wet one.In Kurshab village, many cracks had formed in the dry place.Seven versts (7.5 km) away from this village, there were landslides in the mountains which extended in a meridional direction.In Osh city, the strength of the earthquake was approximately 6-7 degrees [4, 6 and 9].
On May 28, 1926, there was an earthquake, the epicenter of which was 48 km north-east of Osh city.The intensity at the epicenter was 6 (±0.5) degrees.There is no information on earthquake consequences (Seismic catalog of the Institute of Seismology of the National Academy of Sciences of the Kyrgyz Republic).
Naiman earthquake occurred on June 02, 1947 with magnitude of 8 (±1) degrees in epicenter.Buildings shook, doors rattled, windows rattled, many closed doors opened and door frames sagged.People ran out of the premises.Cracks appeared in many of the walls of the adobe houses, some of the walls collapsed and some of the buildings collapsed.The epicenter of the earthquake was in the north-west and 58 km from Osh city.The intensity of the earthquake in Osh city was 5 degrees [1, 6, 7 and 9. Markai (Kok-Yangak) earthquake was on August 03, 1962 with a magnitude of 7-8 (±0.5) degrees.The epicenter of the earthquake was located in the north-east of about 50 km from Osh city.In Osh city the intensity was 5 degrees [6, 7 and 9].The macroseismic information about Kurshab earthquake with magnitude of 6-7 (±0.5) degrees on February 20, 1974 is available.The epicenter of the earthquake was located to the north-east of about 61 km from Osh city.The magnitude of the earthquake in Osh was 5.5 degrees [9].
On October 31, 1991, there was an earthquake with epicenter located to the south-west, approximately 41 km from Osh city (Seismic catalog of the Institute of Seismology of the National Academy of Sciences of the Kyrgyz Republic).
On January 01, 2008 Osh-Kokbel earthquake, 31 km southeast of Osh city occurred (Seismic catalog of the Institute of Seismology of the National Academy of Sciences of the Kyrgyz Republic).
On November 17, 2015 Taldyk earthquake [5] with magnitude of 7 degrees occurred.The epicenter was in the south-east, 39 km from Osh city.The magnitude of the earthquake in Osh city was 5.3 degrees.
In addition, earthquakes with depths of the epicenter from 9 to 55 km were found in the survey area around Osh city.From this we can deduce that the depths of origins of strong earthquakes will apparently depend on the geological crustal structure.

Conclusion
Based on the above information the map of epicenters of the strong earthquakes within the radius of 60 km around Osh city has been created and the summary of destructions in the origin zone and earthquakes on the territory of Osh city has been given.

Fig. 2 .
Fig. 2. The location of strong earthquake epicenters around the area of Osh city and tectonic faults • -epicenters of earthquakes; I -North-Kuva; II -South-Kuva; III -Madin-Taldysu; IV -Kenesh; Va -Katar; Vb -Aldiyar; VI -South-Naukat; VII -Gulch; IX -Uzgen On December 27, 1971, there was an earthquake with epicenter located south-east, 64 km from Osh city.Macroseismic data is not available (Seismic catalog of the Institute of Seismology of the National Academy of Sciences of the Kyrgyz Republic).The macroseismic information about Kurshab earthquake with magnitude of 6-7 (±0.5) degrees on February 20, 1974 is available.The epicenter of the earthquake was located to the north-east of about 61 km from Osh city.The magnitude of the earthquake in Osh was 5.5 degrees[9].On October 31, 1991, there was an earthquake with epicenter located to the south-west, approximately 41 km from Osh city (Seismic catalog of the Institute of Seismology of the National Academy of Sciences of the Kyrgyz Republic).On January 01, 2008 Osh-Kokbel earthquake, 31 km southeast of Osh city occurred (Seismic catalog of the Institute of Seismology of the National Academy of Sciences of the Kyrgyz Republic).On November 17, 2015 Taldyk earthquake[5] with magnitude of 7 degrees occurred.The epicenter was in the south-east, 39 km from Osh city.The magnitude of the earthquake in Osh city was 5.3 degrees.In addition, earthquakes with depths of the epicenter from 9 to 55 km were found in the survey area around Osh city.From this we can deduce that the depths of origins of strong earthquakes will apparently depend on the geological crustal structure.

Table 1 .
The catalog of strong earthquakes within a radius of 60 km from Osh city.