GPS基准站如何跟踪板块运动

How GPS Became a Seismological Tool

Global Positioning System technology, originally developed for military navigation, has become one of the most powerful tools in modern seismology and geodynamics. GPS大地测量利用全球定位系统接收机以毫米级精度测量构造板块运动和地壳变形的方法，可揭示地震之间断层上应变积累的过程。 — the application of GPS measurements to precise ground position tracking — allows scientists to measure 构造板块地球岩石圈中不断移动、漂浮、有时发生断裂的巨大板块。共有7个主要板块和约8个次要板块，它们之间的相互作用引发了绝大多数地震。 movements with millimeter-level accuracy, map the accumulation of strain on fault lines断层在地表的痕迹，表现为一条线状或破碎岩石带。地质学家绘制活动断层线图，以评估周边社区的地震危险性。, detect volcanic inflation, and record the instantaneous co-seismic displacements produced by large earthquakes. The resulting data is foundational to understanding earthquake hazard in ways that seismometry alone cannot provide.

Principles of High-Precision GPS Measurement

Consumer GPS devices achieve accuracy of a few meters by measuring signal travel times from satellites. Geodetic GPS stations achieve millimeter-level accuracy through several additional techniques. Phase-based measurement uses the carrier wave phase (rather than just the coarse ranging signal), which contains far more precise timing information. Differential correction uses a network of reference stations at known positions to remove common atmospheric and clock errors. Long occupation times — continuous recordings over months and years — allow averaging that further reduces noise. The result is position time series accurate to 1–3 mm horizontally and 5–10 mm vertically.

Measuring 构造板块地球岩石圈中不断移动、漂浮、有时发生断裂的巨大板块。共有7个主要板块和约8个次要板块，它们之间的相互作用引发了绝大多数地震。 Velocities

The most fundamental application of GPS大地测量利用全球定位系统接收机以毫米级精度测量构造板块运动和地壳变形的方法，可揭示地震之间断层上应变积累的过程。 is measuring the velocity of tectonic plates relative to each other or to a stable reference frame. The ITRF (International Terrestrial Reference Frame) provides a globally consistent reference against which all GPS station velocities are measured. In plate interiors far from active deformation zones, GPS stations move at the steady plate velocity — typically 2–10 cm/year for major plates. The Pacific Plate moves northwest at approximately 8 cm/year relative to stable North America. The Indian Plate collides into Asia at roughly 5 cm/year, driving the Himalayan orogeny.

Velocity Fields and Strain Accumulation

Near active plate boundaries, the velocity field becomes complex because elastic strain accumulates in the crust rather than being released continuously. At a locked fault因摩擦阻止运动而导致应力持续积累的断层区段。闭锁断层一旦最终破裂，可能引发大地震。, the deep portion of the fault below the seismogenic zone slips freely at plate velocity, but the shallow locked section is held stationary by friction. GPS stations on either side of a locked fault move toward each other at reduced velocity compared to far-field plate motion, and the difference reveals how much strain is accumulating. This "interseismic coupling" measurement is a direct observational constraint on seismic hazard because larger coupling implies greater eventual earthquake potential.

Co-Seismic Displacement: Reading Earthquakes in the GPS Record

When a large earthquake ruptures, the elastic strain accumulated over decades is released instantaneously, and GPS stations near the fault jump to new positions. The 2011 Tohoku earthquake moved GPS stations in northeastern Japan as much as 5.3 meters eastward and 1.2 meters downward — the largest co-seismic displacement ever recorded. The spatial pattern of these displacements, mapped using dozens of stations, revealed the distribution of slip on the fault plane with unprecedented resolution. This slip model directly informs 海啸由水下地震导致海底突然位移而产生的一系列海浪。海啸可以喷气机般的速度（时速700公里以上）穿越整个大洋盆地。 models because the seafloor deformation pattern determines the initial wave shape.

Post-Seismic Relaxation

Following a large earthquake, GPS stations continue to move for months to years as the earth responds to the abrupt stress change through afterslip and viscoelastic relaxation. Afterslip occurs when the fault continues to slip slowly below the seismogenic zone in response to the stress loaded by the main rupture. Viscoelastic relaxation occurs in the lower crust and upper mantle, which flow on geological timescales. GPS time series capture both processes, enabling discrimination between them based on their different spatial patterns and temporal decay rates. Understanding post-seismic deformation is important for 库仑应力传递地震改变邻近断层应力状态、从而可能触发或延迟未来地震的过程，用于预测哪些断层正被推向更接近破裂的状态。 calculations that forecast 余震在同一断层区域内、发生于主震之后的较小地震。余震序列可持续数周至数年，最大余震的震级通常比主震低1.0至1.2级。 sequences.

InSAR Complementing GPS

干涉合成孔径雷达（InSAR）通过对比地震前后拍摄的雷达图像，以厘米级精度测量地表形变的卫星雷达技术，可揭示断层的滑动模式。 (Interferometric Synthetic Aperture Radar) provides spatially dense deformation maps — effectively a GPS measurement at every pixel of a satellite image — but with lower temporal resolution than continuous GPS. GPS provides continuous temporal monitoring at discrete points; InSAR provides snapshot maps covering large areas. The two techniques are complementary: GPS validates and calibrates InSAR products, while InSAR provides spatial context between GPS stations. Together they enabled the first complete maps of interseismic strain accumulation on the San Andreas and other major fault systems.

滑动速率断层沿线位移的平均速率，通常以每年若干毫米衡量。滑动速率越高，通常意味着地震发生频率和危险性越高。 Determination from GPS

Long GPS time series allow direct measurement of 滑动速率断层沿线位移的平均速率，通常以每年若干毫米衡量。滑动速率越高，通常意味着地震发生频率和危险性越高。 — the long-term velocity at which two sides of a fault move relative to each other. For the southern San Andreas Fault, GPS measurements constrain the 滑动速率断层沿线位移的平均速率，通常以每年若干毫米衡量。滑动速率越高，通常意味着地震发生频率和危险性越高。 to approximately 24 mm/year of right-lateral motion. Combining this GPS-derived 滑动速率断层沿线位移的平均速率，通常以每年若干毫米衡量。滑动速率越高，通常意味着地震发生频率和危险性越高。 with the known fault length and historical earthquake record allows calculation of the expected recurrence interval for large ruptures, linking GPS geodesy directly to probabilistic seismic hazard assessment (概率地震危险性分析（PSHA）一种量化地震危险性的方法，综合考虑所有可能的地震震源、震级及地震动水平，以超过特定震动水平的概率来表示结果。).

GPS in Earthquake Early Warning

GPS instruments now play a direct role in earthquake 地震预警（EEW）一种在强震到达前探测地震并向人员和系统发送警报的系统，可提供数秒至数十秒的预警时间，足以采取自我保护行动。 systems. Real-time GPS streams can detect the large co-seismic displacement waves from great earthquakes within tens of seconds, providing magnitude estimates that are not subject to the saturation problems that affect seismometer-based magnitude scales for M 8+ events. The GPS-based magnitude estimate helps ensure that early warning systems issue appropriately scaled alerts for the largest earthquakes, where seismic magnitude underestimation is most consequential.

Continuous GPS Networks

Major continuous GPS networks include the USGS Continuously Operating Reference Stations (CORS), the Southern California Integrated GPS Network (SCIGN), the Japanese GEONET (1,300+ stations), and the UNAVCO Plate Boundary Observatory. Data from these networks is archived and freely available, enabling retrospective analysis of deformation events and routine updating of tectonic models. New constellations beyond GPS — including Russia's GLONASS, Europe's Galileo, and China's BeiDou — are being integrated into geodetic networks, improving coverage and redundancy.

Summary

GPS大地测量利用全球定位系统接收机以毫米级精度测量构造板块运动和地壳变形的方法，可揭示地震之间断层上应变积累的过程。 transformed seismology from a science that only observes earthquakes when they happen into one that can monitor the slow accumulation of strain that precedes them. By measuring 构造板块地球岩石圈中不断移动、漂浮、有时发生断裂的巨大板块。共有7个主要板块和约8个次要板块，它们之间的相互作用引发了绝大多数地震。 velocities, mapping interseismic coupling, recording co-seismic displacements, and tracking post-seismic relaxation, GPS provides the most complete observational picture of the earthquake cycle available. Combined with 干涉合成孔径雷达（InSAR）通过对比地震前后拍摄的雷达图像，以厘米级精度测量地表形变的卫星雷达技术，可揭示断层的滑动模式。 and traditional seismometry, geodetic GPS is indispensable to modern seismic hazard assessment and 滑动速率断层沿线位移的平均速率，通常以每年若干毫米衡量。滑动速率越高，通常意味着地震发生频率和危险性越高。 quantification.