R/S analysis of earthquake time interval

The R/S analysis method of time series was suggested by Hurst in 1965, then it was used tostudy the fractional Brownian motion(FBM) and the self--affinity of natural phenomena (MandeLbrot and Wallis, 1969a 3 Feder, 1988). In this paper, we use R/S analysis method to study thechsnges of Hurst exponent H of time interval sequences Of earthquakes with time variations for 5r%ions as follows: Wuqia (38'--41'N, 73'- 77 'E, M.>3' 5) I Tangshan (38'-41'N,116. 5'-- 119. 5'E, ML 2 3); Longling (23'- 26'N, 97'-- 100'E, ML > 3); Songpan (31'- 34'N,102. 5'- 105. 5'E, ML;3); China and its vicinity (20'- 50'N, 73'-129'E, M,>5), andmake an attempt to find features of anomalous variations of H values before the moderate strongearthquakes.

Paleo-earthquake studies on the eastern section of the Kunlun fault

Roughly along the Animaqing Maji peak, the Kunlun fault section between the Tuosuo Lake and Kendingna (east Maqin) can be subdivided into two geometric segments: the Huashixia and the Maqin segments. These two segments behave differently in their Holocene slip rates and paleo-earthquake activities, with obviously higher paleo-seismic activity on the Huashixia segment than on Maqin segment. As many as four strong Holocene earthquakes are identified on the Huashixia segment from trenching and geomorphic studies. The recurrent interval for the latest three earthquakes are at about 500 a and 640 a, respectively. On the Maqin segment, at least three paleo-earthquake events can be defined from trenching, with a recurrent interval for the latest two events at about 1000 a. M = 7.5 earthquakes on Huashixia segment recur at every 411 a to 608 a with a characteristic slip at 5.75±0.57 m. Although the Maqin segment is less active, its accumulated strain energy during the long time period since last earthquake occurred (about 1070 a BP) deserves enough notice on its future earthquake probabilities.

The Holocene Activity Evidence of the Yema River-Daxue Mountain Fault in Western Qilian Mountain

Altyn Tagh fault controls the deformation characteristics of the northern margin of the Qinghai-Tibet Plateau.The sinistral slip rate of the eastern segment of the fault reduces gradually where the reduction transforms into the deformation within Qilian Mountain,forming a series of thrust faults and strike-slip faults.Among them,the Yema River-Daxue Mountain fault is one of the important structural transform faults in the study area.Based on the differences of the geometrical characteristics and activities,the fault is divided into four segments,the Yema River segment,the Shibandun segment,the Liushapo segment and the Baishitougou segment,among which the former three are Holocene active faults,and the Baishitougou segment belongs to late Pleistocene fault.The excavated trenches imply a total of 6 paleoearthquake events,and at least 4 events have occurred during Holocene,whose occurrence times are 8300±700 yr BP,6605±140 yr BP,4540±350 yr BP,2098±47 yr BP,respectively.The recurrence interval is 2600±600 yr BP that is close to the lapsed time of the last one,2098±47 yr BP,which suggests that the Yema River-Daxue Mountain fault is in a high risk of major earthquakes in the future.The vertical coseismic displacements of the four Holocene paleoearthquake events are 100 cm,42 cm,40 cm and 50 cm,respectively,the horizontal coseismic displacements are 5 m,4.5-5.5 m,5-8 m and 4-5.5 m,separately,and then the reference magnitude of the paleoearthquake events is conjectured to be M7.6±0.1.

Preliminary analysis of earthquake probability based on the synthetic seismic catalog

The analysis of seismic hazards relies on the statistical analysis of historical seismic data and the instrumental seismic catalog to obtain the regional earthquake recurrence interval and earthquake probability.The accuracy of analysis thus depends strongly on the completeness of the seismic data used.However,available seismic catalogs are too short or incomplete for the reliable analysis of the statistical characteristics of earthquakes.If a long-term synthetic seismic catalog can be generated using a physics-based numerical simulation,and the simulation results match the crustal deformation,seismicity,and other observations,then such a synthetic catalog helps us to further understand the characteristics of seismic activity and analyze the regional seismic hazard.In this paper,taking the northeastern Tibetan Plateau as a case study,we establish a three-dimensional visco-elastoplastic finite-element model to simulate earthquake cycles and the spatiotemporal evolution of earthquakes on the model fault system and obtain a seismic catalog on a time scale of tens of thousands of years.On the basis that the model satisfies the regional geodynamics of the northeastern Tibetan Plateau,we analyze seismicity on the northeastern Tibetan Plateau using the simulated synthetic earthquake catalog.The characteristics of earthquake recurrence at different locations and different magnitudes,and the long-term average probability of earthquake occurrence within the fault system on the northeastern Tibetan plateau are studied.The results are a reference for regional seismic hazard assessment and provide a basis for the physics-based numerical prediction of earthquakes.