地震机理的地球系统科学研究及预测实践

Earth system science research on earthquake mechanisms:Theory and validation of a new model

本文提出了一个新的地震机理模型:高温高压高导低速流变体震源腔(简称震源腔)与闭锁断层组合模型。高温高压下的软流圈物质在复杂相变空间中,受到温度场中的异重流作用和受迫振动作用而形成深源震源腔。随着软流圈物质上涌,幔汁在温度差和压力差驱使下,涌入地壳中的物理空间,形成浅源地震震源腔。由于温度升高使得腔体内岩石部分熔融或全部熔融,释放出大量气液流体,拓展腔体空间范围,同时提升腔体内压。当腔体内部有效压力(即内压与上覆地壳压力之差)达到腔体边缘或者上方与脆性活动断层交会部位的岩石破坏强度时,震源腔便进入临界状态。当软流圈物质上涌继续向腔体内供能,或者由于星体连线在震源区造成触发作用,便引起震源腔的隐蔽爆炸,即隐爆,释放腔体内部积累的能量,同时释放区域构造应力场作用于闭锁断层积累的应变能。腔体隐爆释放能量与腔体规模正相关。闭锁断层释放应变能与闭锁断层规模、闭锁区大小以及区域构造应力场强度相关。震源腔与脆性活动断层交会部位,是潜在震源位置。多年观测资料表明,震源腔从进入临界状态到隐爆,一般经历1~13天,平均7天。长期观测表明,潜在震中区在震前经常出现干旱、气温升高、海温升高、大量水汽释放等异常现象。通过超低频地震仪监测、重力波作用于水汽形成的地震云的观测、次声波的监测、卫星重力异常反映的高程面垂向震荡监测、以及地基卫星导航系统地面升降监测等,都显示出震源腔进入临界状态后的胀缩震荡引起震中及其外围地面的垂向振动。文中还给出了震源腔体隐爆遗迹的直接证据。对于被主流地震界和主流气象界长期否定的地震云是否存在问题,从地震机理和观测实践两个方面,给与了充分肯定。认为腔体震荡在空气中产生的重力波和震源腔内携带离子的流体涡旋电场感应磁场作用于水汽,是地震云形成的两个物理机制。山东金伯利岩管中的椭球状隐爆角砾岩的斜列组合以及地球南、北半球岩浆底辟螺旋侵位岩体的发现,记录了这种流体螺旋状上升的真实过程。单智伟团队在西安雾霾中收集到1081个金属微颗粒中多见含铬、钛等成分的浑圆状球状重金属微粒的事实,为地壳排气来自幔源提供了物证。本文展示了2010年1月13日海地7.0级地震、2015年4月25日尼泊尔8.2级地震、2017年8月8日九寨沟7.0级地震的震前排气卫星云图。利用层析成像技术,圈定出了汶川8.0级巨震(20080512)的震源腔形态、规模和位置,发现汶川巨震震源恰好处于震源腔顶部与龙门山脆性活动断层带交会部位。对于九寨沟震源区及其附近2002年1月1日以后12年期间的重力扰动数据和该区3.0级以上地震目录进行了统计分析。结果显示,该区重力异常扰动显示出6.0级地震前的等效高程震荡幅差平均值达到3.9 cm,震级与高程震荡幅值成正比。利用108个断层面解求得渤海湾及其外围的构造应力场,发现在唐山地震和海城地震震源腔上方及其北东侧附近,正好都存在一个对应的应力场异常区。间接证明震源腔内高压对于震源区局部应力场的影响。利用海水表面温度异常,笔者成功预测了2021年5月1日日本本州岛东海岸近海6.7级地震震中位置。另外,利用干旱和气温异常,笔者提前两天预测了2019年6月24日云南楚雄4.8级地震震中位置。这为震源腔模型的应用提供了实践案例。根据震源腔临界状态内部离子随着热流体涡旋状流动产生地电场的频率特征,我们研制了一台DD108地电仪。单台站可以预测全球7级以上地震发生的时间(异常出现后1~13天,平均7天)和震级。文中给出了一些实际案例,包括2017年8月8日九寨沟7.0级地震、2021年5月22日青海玛多7.4级地震、2021年9月8日墨西哥7.1级地震等。

A combined model of seismic source cavity and latching fault for earthquake mechanism is proposed.Deep seismic source cavities are formed by the anomaly gravity flow and forced vibration of the high temperature,high pressure asthenosphere materials in the complex phase transition space of the temperature field.It is common that the mantle fluids,driven by temperature and pressure differences,are transferred from mantle to crust to form source cavities for shallow earthquakes.Due to the temperature rise,the continuous partial and/or full melting of the wallrocks cause the cavity to expand,increasing the pressure inside the cavity.When the effective pressure(i.e.,the difference between the internal pressure and the pressure of overlying crust)inside the cavity reaches the failure strength of wall rock at the edge or top of the cavity where wall rock is connected to the relatively brittle active fault(s),the cavity comes to a crucial state.When the asthenosphere continues to supply energy to the cavity,or when the cavity is triggered by earth tide resulted from the alignment of the celestial bodies to the source region,cryptoexplosion occurs to release the energy accumulated in the cavity plus the strain energy accumulated from regional tectonic stress field acting on the latching active fault(s).In this model,the intracavity energy released from cryptoexplosion is positively correlated with the cavity size,while the released strain energy is related to the size and asperity of the fault(s)as well as to the intensity of the regional tectonic stress field.The junction between the source cavity and the relatively brittle active fault(s)is a potential hypocenter of the impending earthquake.Source cavities generally develop in 1 to 13 days,averaging 7 days,from entering the crucial state to cryptoexplosion.After long-term observations we theorize that the abnormal phenomena,such as drought,temperature rise,sea surface temperature rise and water vapor release,often occur in the potential earthquake area before the earthquake.Direct evidence for the seismic source cavity cryptoexplosion are also introduced.Based on long-term observations and the seismic source cavity model,we give full affirmation to seismic clouds which have long been denied by seismological and meteorological circles.We consider that the gravitational wave generated by the cavity oscillation in the air,and the magnetic field induced by the eddy flow of fluid in the cavity acting on water vapor,are the physical mechanism of the formation of seismic clouds.Here we show the satellite images of releasing aqueous vapour prior to the M 7.0 Haiti earthquake on January 13,2010,the M 8.2 Gorkha(Nepal)earthquake on April 25,2015,and the M 7.0 Jiuzhaigou earthquake on August 8,2017.By use of seismic tomography technique,the shape and size of the seismic source cavity for the M 8.0 Wenchuan giant earthquake(May 12,2008)were determined.We found that the hypocenter of the Wenchuan earthquake lies at the junction between the top of the source cavity and the Longmenshan brittle active faults.We performed statistical analysis on the gravity disturbance data of the Jiuzhaigou earthquake area and its vicinity,collected during the 12 years since January 1,2002,and on the catalogue of the area s earthquakes equal or above M 3.0.The results show that the equivalent elevation amplitude change attributable to gravity anomaly was 3.9 cm before the M 6 earthquake,and the magnitude of earthquake was proportional to the magnitude of elevation oscillation by statistical comparison.Based on the tectonic stress field obtained from 108 fault plane solutions for the Bohai Bay and its periphery,we found that there are abnormal stress fields above and to the northeast side of the source cavities in both the Tangshan and Haicheng earthquakes.This points to the effect of high pressure in the source cavity on regional tectonic stress field.By using the abnormal sea surface temperature,ZENG Zuoxun successfully predicted the epicenter location of the M 6.7 earthquake on May 1,2021 off the coast of Honshu Island,Japan.Using drought and temperature anomalies,he correctly predicted two days in advance the epicenter location of the M 4.8 Chuxiong earthquake on June 24,2021 in Yunnan Province.Based on the frequency characteristics of the geoelectric field generated by the eddy flow of ions in the crucial state of the cavity,we developed a DD108 geoelectric instrument.With the single station observation we can predict(within 113 days after the occurrence of the anomaly,averaging 7 days)the occurring time and the magnitude of a coming earthquake.Some examples are shown in the paper,including the M 7.0 Jiuzhaigou earthquake in 2017,and the M 7.4 Qinghai Maduo and M 7.1 Mexico earthquakes in 2021.