The MW5.5 earthquake on August 6,2023,in Pingyuan,Shandong,China:A rupture on a buried fault

On August 6,2023,a magnitude MW5.5 earthquake struck Pingyuan County,Dezhou City,Shandong Province,China.This event was significant as no large earthquakes had been recorded in the region for over a century,and no active fault had been previously identified.This study collects 1309 P-wave arrival times and 866 S-wave arrival times from 74 seismic stations less than 200 km to the epicenter to constrain the spatial distribution of the mainshock and its 125 early aftershocks by the double difference earthquake relocation method,and selects 864 P-waveforms from 288 stations located within 800 km of the epicenter to constrain the focal mechanism solution of the mainshock through centroid moment tensor inversion.The relocation and the inversion indicate,the Pingyuan MW5.5 earthquake was caused by a rupture on a buried fault,likely an extensive segment of the Gaotang fault.This buried fault exhibited a dip of approximately 75°to the northwest,with a strike of 222°,similar to the Gaotang fault.The rupture initiated at the depth of 18.6 km and propagated upward and northeastward.However,the ground surface was not broken.The total duration of the rupture was~6.0 s,releasing the scalar moment of 2.5895×1017 N·m,equivalent to MW5.54.The moment rate reached the maximum only 1.4 seconds after the rupture initiation,and the 90%scalar moment was released in the first 4.6 s.In the first 1.4 seconds of the rupture process,the rupture velocity was estimated to be 2.6 km/s,slower than the local S-wave velocity.As the rupture neared its end,the rupture velocity decreased significantly.This study provides valuable insights into the seismic characteristics of the Pingyuan MW5.5 earthquake,shedding light on the previously unidentified buried fault responsible for the seismic activity in the region.Understanding the behavior of such faults is crucial for assessing seismic hazards and enhancing earthquake preparedness in the future.

Rapid source inversions of the 2023 SE Türkiye earthquakes with teleseismic and strong-motion data

We conducted rapid inversions of rupture process for the 2023 earthquake doublet occurred in SE Türkiye,the first with a magnitude of M_(W)7.8 and the second with a magnitude of M_(W)7.6,using teleseismic and strong-motion data.The teleseismic rupture models of the both events were obtained approximately 88 and 55 minutes after their occurrences,respectively.The rupture models indicated that the first event was an asymmetric bilateral event with ruptures mainly propagating to the northeast,while the second one was a unilateral event with ruptures propagating to the west.This information could be useful in locating the meizoseismal areas.Compared with teleseismic models,the strong-motion models showed relatively higher resolution.A noticeable difference was found for the M_(W)7.6 earthquake,for which the strong-motion models shows a bilateral event,rather than a unilateral event,but the dominant rupture direction is still westward.Nevertheless,all strong-motion models are consistent with the teleseismic models in terms of magnitudes,durations,and dominant rupture directions.This suggests that both teleseismic and strong-motion data can be used for fast determination of major source characteristics.In contrast,the strong-motion data would be preferable in future emergency responses since they are recorded earlier and have a better resolution ability on the source ruptures.

Quick moment tensor solution for 6 April 2009,L'Aquila,Italy,earthquake

A Mw6.4 earthquake occurred in L＇Aquila, central Italy at 1：32：42 （UTC）, April 6, 2009. We quickly obtained the moment tensor solution of the earthquake by inverting the P waveforms of broadband recordings from the global seismographic network （GSN） stations using the quick technique of moment tensor inversion, and further inferred that the nodal plane of strike 132°, dip 53° and rake -103° is the seismogenic fault.

Fast and robust inversion of earthquake source rupture process and its application to earthquake emergency response

Fast inversion of source rupture process for significant earthquake is introduced and applied to earthquake emergency response. We retrieve and use the apparent source time functions （ASTFs） to stabilize the rupture process inversion, aiming to get the rupture process results correctly and quickly. The applications to 22 significant earthquakes occurred between January 2009 and July 2011 show an average inversion time consumed of about four hours, suggesting a high efficiency of this method, which much improves the inversion speed of the rupture process and is helpful in earthquake disaster mitigation and relief.

Rupture process of the 2011 Tohoku earthquake from the joint inversion of teleseismic and GPS data

Teleseismic and GPS data were jointly inverted for the rupture process of the 2011 Tohoku earthquake. The inversion results show that it is a bilateral rupture event with an average rupture velocity less than 2.0 km/s along the fault strike direction. The source rupture process consists of three sub-events, the first oc- curred near the hypocenter and the rest two ruptured along the up-dip direction and broke the sea bed, causing a maximum slip of about 30 m. The large-scale sea bed breakage may account for the tremendous tsunami disaster which resulted in most of the death and missing in this mega earthquake.

The 2018 M_S 5.9 Mojiang Earthquake:Source model and intensity based on near-field seismic recordings

On September 8, 2018, an M_S 5.9 earthquake struck Mojiang, a county in Yunnan Province, China. We collect near-field seismic recordings(epicentral distances less than 200 km) to relocate the mainshock and the aftershocks within the first 60 hours to determine the focal mechanism solutions of the mainshock and some of the aftershocks and to invert for the finite-fault model of the mainshock.The focal mechanism solution of the mainshock and the relocation results of the aftershocks constrain the mainshock on a nearly vertical fault plane striking northeast and dipping to the southeast. The inversion of the finite-fault model reveals only a single slip asperity on the fault plane. The major slip is distributed above the initiation point, ～14 km wide along the down-dip direction and ～14 km long along the strike direction, with a maximal slip of ～22 cm at a depth of ～6 km. The focal mechanism solutions of the aftershocks show that most of the aftershocks are of the strike-slip type, a number of them are of the normal-slip type, and only a few of them are of the thrust-slip type.On average, strike-slip is dominant on the fault plane of the mainshock, as the focal mechanism solution of the mainshock suggests, but when examined in detail, slight thrust-slip appears on the southwest of the fault plane while an obvious part of normal-slip appears on the northeast, which is consistent with what the focal mechanism solutions of the aftershocks display. The multiple types of aftershock focal mechanism solutions and the slip details of the mainshock both suggest a complex tectonic setting, stress setting, or both. The intensity contours predicted exhibit a longer axis trending from northeast to southwest and a maximal intensity of Ⅷ around the epicenter and in the northwest.

Which velocity model is more suitable for the 2017 M_S7.0 Jiuzhaigou earthquake?

On Aug.8, 2017, an M_S 7.0 earthquake struck Jiuzhaigou, a county of Sichuan province, China. A number of investigations and studies have been conducted, some of which involved local velocity models. However, the suitability of these models has not been properly addressed. Here we collect 11 already-existing models, including those used in studies of the 2017 M_S 7.0 Jiuzhaigou earthquake,choose 10 local stations surrounding the earthquake, and employ the same technique(TRIT) to relocate the hypocenter. And furthermore, we choose a more suitable model from the 11 already-existed models by analyzing the relocation process and the relocated results for reasonability. Finally, our conclusion is that the model Fang 2018 is more suitable and the hypocenter parameters, 103.801°E,33.192°N and 15.8 km for longitude, latitude and depth, respectively, and 2017-08-08 13:19:46.66 for its origin time, based on this model should be recommended for the 2017 M_S7.0 Jiuzhaigou earthquake.

Source complexity of the 2016 M_W7.8 Kaikoura (New Zealand) earthquake revealed from teleseismic and InSAR data

On November 13, 2016, an MW7.8 earthquake struck Kaikoura in South Island of New Zealand. By means of back-projection of array recordings, ASTFs-analysis of global seismic recordings, and joint inversion of global seismic data and co-seismic In SAR data, we investigated complexity of the earthquake source. The result shows that the 2016 MW7.8 Kaikoura earthquake ruptured about 100 s unilaterally from south to northeast(~N28°–33°E), producing a rupture area about 160 km long and about 50 km wide and releasing scalar moment 1.01×1021 Nm. In particular, the rupture area consisted of two slip asperities, with one close to the initial rupture point having a maximal slip value ~6.9 m while the other far away in the northeast having a maximal slip value ~9.3 m. The first asperity slipped for about 65 s and the second one started 40 s after the first one had initiated. The two slipped simultaneously for about 25 s.Furthermore, the first had a nearly thrust slip while the second had both thrust and strike slip. It is interesting that the rupture velocity was not constant, and the whole process may be divided into 5 stages in which the velocities were estimated to be 1.4 km/s, 0 km/s, 2.1 km/s, 0 km/s and 1.1 km/s, respectively. The high-frequency sources distributed nearly along the lower edge of the rupture area, the highfrequency radiating mainly occurred at launching of the asperities, and it seemed that no high-frequency energy was radiated when the rupturing was going to stop.

Fast inversion of rupture process of the 14 April 2010 Yushu,Qinghai,earthquake

Four results of the rupture process of 14 April 2010 Yushu, Qinghai, earthquake, obtained by inverting the broadband seismic data of Global Seismographic Network （GSN） based on the inversion method of earthquake rupture process, were compared and discussed. It is found that the Yushu earthquake has several basic characteristics as follows： 1 There exist two principal sub-events which correspond to two slip-concentrated patches being located near the hypocenter and to the southeast of the epicenter. The rupture of the slip-concentrated patch to the southeast of the epicenter broke though the ground surface; 2 The peak slip and peak slip-rate are about 2.1 m and 1.1 m/s, respectively, indicating that the Yushu earthquake is an event with large slip-rate on the fault plane; 3 Overall the Yushu earthquake is a unilateral rupture event with the rupture mainly propagating southeastward. The strong focusing of the seismic energy in the southeast of the epicenter due to the ＂seismic Doppler effect＂ reasonably accounts for the tremendous damage in the Yushu city.

Preliminary analysis of the shear-wave splitting observations from the Qiaojia seismic array

A total of 351 shear-wave splitting results at 25 stations were obtained from the seismic data recorded in period of January,2013 to December,2016,by a broadband seismic array deployed in the northern segment of Xiaojiang Fault Zone(n-XJFZ).Meanwhile,the stress field of the n-XJFZ was determined by inverting 140 focal mechanism solutions of the small earthquakes within the study area which were recorded in the same period.This determination confirmed a compressive stress in NW-SE orientation and an extensional stress in the NE-SW orientation,with little difference from those released by previous studies.The shear-wave splitting results show a spatial complexity in polarization orientation,different from one site to another.How-ever,the polarization orientations integrated for the subareas suggest that the fault trends seemingly played important roles.All the subareas bear two dominant orientations,N10°E and N90°E,both of which are different from the azimuths of the principal compressive stress,due to the fault distribution.The time delay averaged over the entire region is 4.56 ms/km,close to that of the upper boundary of the generally accepted interval worldwide but larger than those in most of the investigated regions in the Chinese mainland,which probably implies an alignment of more micro-cracks in the n-XJFZ.Interestingly,the 2014 Ms6.5 Ludian earthquake was found to have caused a variation in the time delays of the slow shear waves within the study area though its epicenter was outside.This earthquake resulted in an evident drop of the time delays remaining for 4 months,however,lifted a bit the time-delay level with respect to that prior to the earthquake.

Preface to the special issue on complicated features on seismic sources and deep structures

Earthquake is a kind of natural phenomenon in the Earth.Earthquake seismology has been developed quickly since modern digital seismometers were applied to observations.From seismic records,seismologists study source properties of the earthquakes and detect multi-scale structural variations in the crust,mantle,and core.Earthquake is complicated,including seismicity and seismic sources.

Error Sensitivity Analysis in 10–30-Day Extended Range Forecasting by Using a Nonlinear Cross-Prediction Error Model

Extended range forecasting of 10-30 days, which lies between medium-term and climate prediction in terms of timescale, plays a significant role in decision-making processes for the prevention and mitigation of disastrous met- eorological events. The sensitivity of initial error, model parameter error, and random error in a nonlinear cross- prediction error （NCPE） model, and their stability in the prediction validity period in 1 0-30-day extended range fore- casting, are analyzed quantitatively. The associated sensitivity of precipitable water, temperature, and geopotential height during cases of heavy rain and hurricane is also discussed. The results are summarized as follows. First, the initial error and random error interact. When the ratio of random error to initial error is small （10＂5-10-2）, minor vari- ation in random error cannot significantly change the dynamic features of a chaotic system, and therefore random er- ror has minimal effect on the prediction. When the ratio is in the range of 10-1-2 （i.e., random error dominates）, at- tention should be paid to the random error instead of only the initial error. When the ratio is around 10 2-10-1, both influences must be considered. Their mutual effects may bring considerable uncertainty to extended range forecast- ing, and de-noising is therefore necessary. Second, in terms of model parameter error, the embedding dimension m should be determined by the factual nonlinear time series. The dynamic features of a chaotic system cannot be depic- ted because of the incomplete structure of the attractor when m is small. When m is large, prediction indicators can vanish because of the scarcity of phase points in phase space. A method for overcoming the cut-off effect （m 〉 4） is proposed. Third, for heavy rains, precipitable water is more sensitive to the prediction validity period than temperat- ure or geopotential height; however, for hurricanes, geopotential height is most sensitive, followed by precipitable water.

Source process of the 2010 Yushu,Qinghai,earthquake

The comprehensive waveform analysis of the Love waves and P waves shows that the Yushu M S7.1 (M W6.9) earthquake consists of two distinct sub-events. The first one occurred in the first 5 s releasing less seismic moment, and the second occurred in the later 11 s releasing more seismic moment. Spatially, the first sub-event surrounded the hypocenter, and the second, about 30 km away from the first, was much closer to the Yushu city and broke through the ground surface. In terms of the rupture velocity to which the peak values of the two sub-events correspond, the first sub-event propagated with an average rupture velocity of 1.6 km/s, however, the second propagated with an average rupture velocity of 4.0 km/s which is actually superior to the shear-wave velocity in the hypocentral region. The magnitude of the Yushu earthquake is in the lower margin of large earthquakes. The results obtained in this study indicate that the super-shear rupture possibly appears in earthquakes with magnitude of around 7.0, instead of only in the great earthquakes with magnitude around 8.0 [14, 15]. In addition, the energy focusing caused by the super-shear rupture should take key responsibility for the tremendous damage to the Yushu city as well as the ground-surface breakage related to the larger second sub-event.

Noninvasive Ultrasound Stimulation of Ventral Tegmental Area Induces Reanimation from General Anaesthesia in Mice

Evidence in animals suggests that deep brain stimulation or optogenetics can be used for recovery from disorders of consciousness(DOC).However,these treatments require invasive procedures.This report presents a noninvasive strategy to stimulate central nervous system neurons selectively for recovery from DOC in mice.Through the delivery of ultrasound energy to the ventral tegmental area,mice were aroused from an unconscious,anaesthetized state in this study,and this process was controlled by adjusting the ultrasound parameters.The mice in the sham group under isoflurane-induced,continuous,steady-state general anaesthesia did not regain their righting reflex.On insonation,the emergence time from inhaled isoflurane anaesthesia decreased(sham.13.63±0.53 min,ultrasound.1.5±0.19 min,p<0.001).Further,the induction time(sham.12.0±0.6 min,ultrasound.17.88±0.64 min,p<0.001)and the concentration for 50%of the maximal effect(EC50)of isoflurane(sham.0.6%,ultrasound.0.7%)increased.In addition,ultrasound stimulation reduced the recovery time in mice with traumatic brain injury(sham.30.38±1.9 min,ultrasound.7.38±1.02 min,p<0.01).This noninvasive strategy could be used on demand to promote emergence from DOC and may be a potential treatment for such disorders.

Single-and multiple-scattering properties of ice crystals in 1.38 μm wavelength and its potential applications in satellite remote sensing

An improved ray-optics theory and Mie theory for single scattering and the adding-doubling method for multiple scattering are used to study the relationship between the radiation in the wavelengths of 1.38, 3.979, 6.5, and 11.03 μm and the microphysics of cirrus clouds. It is shown that the strong 1.38 μm water vapor band in the near-IR region is superior to the other three IR channels used in current operational satellites and has potential possibility of remote sensing of microphysical and optical properties of cirrus clouds.