矩震级是如何定义的，它为何比里氏震级更适合描述巨型地震？
How is moment magnitude defined, and why does it suit great earthquakes better than the Richter scale?
矩震级由地震矩决定，等于岩石剪切模量、破裂面积与平均滑移量的乘积，直接反映破裂规模。里氏震级在极大地震上会饱和，无法区分能量差异，而矩震级在整个范围内都近似线性。汉克斯与金森博在1979年提出它，如今已成为地震学标准标度。
Moment magnitude is based on seismic moment, the product of rock rigidity, rupture area, and average slip, and the scale grows roughly linearly across all sizes. The Richter scale saturates for very large events and cannot distinguish their energy, whereas moment magnitude does not. Hanks and Kanamori introduced it in 1979, and it is now the standard seismological scale.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#矩震级 #地震矩 #里氏震级
岩石在六百公里深处的高温高压下应当发生塑性流动,深源地震究竟是怎样'断裂'出来的?
Rock at ~600 km depth should deform plastically rather than fracture — so how do deep-focus earthquakes manage to 'rupture' at all?
主流解释围绕三条线索展开:亚稳态橄榄石在过渡带仍暂时保存并发生相变,相变失稳产生的裂纹状缺陷可触发滑动;矿物脱水带来的孔隙压骤升能削弱断层面;细粒化的热塑性剪切带也可能高速失稳。日本海沟下方俯冲板片内观测到的滞留冷物质与深震分布相互印证,但单一机制尚无定论,仍是地球内部物理的前沿问题。
Three candidate mechanisms dominate: metastable olivine surviving into the transition zone, whose transformational faulting nucleates slip; dehydration embrittlement, where released fluids spike pore pressure and weaken faults; and thermal runaway on localized fine-grained shear zones. Seismic imaging of cold slabs beneath Japan matches the depth distribution of deep events, supporting the framework, yet no single mechanism is settled and the problem remains a frontier of deep-Earth physics.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-04结论有争议 · Contested
来源 · Source
Green 与 Houston,《The Mechanics of Deep Earthquakes》,Annual Review of Earth and Planetary Sciences,1995 (DOI: 10.1146/annurev.ea.23.050195.001125)
Green & Houston, 'The Mechanics of Deep Earthquakes', Annual Review of Earth and Planetary Sciences, 1995, DOI: 10.1146/annurev.ea.23.050195.001125
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1146/annurev.ea.23.050195.001125
#深源地震 #亚稳态橄榄石
海啸通常由什么触发，沿海居民如何识别其前兆？
What usually triggers a tsunami, and how can coastal residents recognize its warning signs?
大多数海啸由海底地震突然抬升或沉降海床引发，少数来自海底滑坡或火山喷发。最直观的前兆是海水在数分钟内异常退去，露出大片海床，随后巨浪袭来。美国海洋大气管理局的海啸预警中心与Synolakis的研究都强调了这一退潮信号。
Most tsunamis are triggered by submarine earthquakes that abruptly uplift or drop the seafloor, with a few from underwater landslides or eruptions. The clearest warning is the sea rapidly retreating far offshore within minutes, exposing the seabed before the wave arrives. NOAA's Tsunami Warning Center and Synolakis's work both stress this drawdown signal.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#海啸 #海底地震 #退潮前兆
P波和S波在地球内部传播的行为如何帮助划分地球圈层？
How do the behaviors of P and S waves inside Earth help delineate its layers?
P波是纵波、可在固液气体中传播，S波是横波、只能穿过固体，二者速度随介质密度与刚性变化。S波在约2900公里深处突然消失，揭示其下方为液态外核；P波的折射则勾勒出内外核边界。莱曼在1936年据此发现了固态内核。
P waves are compressional and travel through solids, liquids, and gases, while S waves are shear waves that pass only through solids, and both change speed with density and rigidity. S waves vanish abruptly near 2,900 km depth, revealing the liquid outer core below, and P-wave refraction outlines the inner-core boundary. Lehmann used this in 1936 to discover the solid inner core.
难度 进阶 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#P波 #S波 #地球分层
同一次地震只对应一个震级,为什么各地报告的破坏程度却能相差悬殊?
One earthquake corresponds to a single magnitude, so why can reported damage vary dramatically from place to place?
震级度量的是震源释放的能量,属于地震自身的属性;烈度刻画的是某一地点感受到的震动强弱,取决于震中距、传播路径和场地条件。软弱土层会有选择性地放大某些频段的震动,使得位于软土盆地上的城市遭受的破坏反而可能超过离破裂带更近的基岩场地。
Magnitude measures the energy released at the source and is an intrinsic property of the event, whereas intensity describes how strongly shaking is felt at a given site, governed by distance, propagation path, and ground conditions. Soft soils selectively amplify particular frequency bands, so a city sitting on a soft basin can be hit harder than rock sites much closer to the rupture.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Tarbuck & Lutgens,《Earth Science》第14版,Pearson,2015
E. J. Tarbuck and F. K. Lutgens, Earth Science, 14th ed., Pearson, 2015
#震级与烈度 #场地效应
全球地震台网如何在震后几分钟内定出一次远震的位置?P波与S波的到时差在其中起了什么作用?
How can a global network of seismic stations pin down a distant earthquake within minutes of its occurrence, and what part does the P-minus-S arrival-time gap play?
P波比S波跑得快,单台记录上两者的到时差随震中距增大而拉大,可直接换算出台站到震源的距离。一个距离只确定一个球面,至少三个台站的距离圆弧相交才能锁定震中,震源深度则依靠更多台站的到时残差联合求解。现代定位程序以速度模型对所有到时做最小二乘拟合,快速给出震中、深度和发震时刻。
P waves outrun S waves, and at each station the widening gap between their arrivals converts directly into a source-to-station range. One range defines only a sphere, so arcs drawn from at least three ranges must intersect to fix the epicenter, while depth is constrained jointly by residuals at many more stations. Modern location codes fit a velocity model to all observed arrivals by least squares, delivering epicenter, depth, and origin time almost immediately.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
Kennett 与 Engdahl 1991 年发表于《Geophysical Journal International》的IASPEI 91全球走时表
B. L. N. Kennett, E. R. Engdahl, Traveltimes for global earthquake location and phase identification, Geophysical Journal International, 1991
独立核验依据 · Independent verification: 核验依据 1 CROSSREF 标识 10.1111/j.1365-246x.1991.tb06724.x：Traveltim
#地震定位 #走时差