On March 6, 1978, during a press conference, Tadao Kenta, the mayor of Nara City, Japan, pointed to a cloud in the northern sky and stated, "This is an earthquake cloud; a strong earthquake will soon impact a large area of Japan." The very next day, a 7.8 magnitude earthquake indeed occurred in the nearby sea.
The use of earthquake clouds for predicting seismic activity has garnered significant attention in academic circles. This method is easy to observe and requires no equipment, making it appealing not only to professional seismologists but also to amateur enthusiasts eager to test its validity.
As a novel approach, Tadao Kenta faced challenges. The Earthquake Prediction Liaison Committee for the Tokai region is Japan's highest authority on earthquake prediction, and its experts believe that this method could cause public confusion and lacks scientific value. Professor Takashi Ogiwara from the University of Tokyo argues that the concept of earthquake clouds is purely coincidental. Even experts from the Japan Meteorological Agency have noted that the earthquakes Kenta recorded were sometimes far from Japan's mainland or occurred at depths of hundreds of kilometers beneath the sea, making it impossible for any precursors to manifest in the atmosphere above Japan.
Earthquake clouds appear in the sky, but why can some people identify earthquake-related clouds among ordinary ones? What shapes of clouds are associated with earthquakes?
Chinese researchers have discovered that earthquake clouds are complex in color, often displaying shades like iron gray, orange-yellow, and orange-red. These clouds typically appear in the early morning or evening, with their distribution direction perpendicular to the epicenter. Some individuals have successfully predicted the location of earthquakes based on this pattern. Chinese seismologist Lü Dajiong compiled a distribution map of earthquake clouds, identifying the ground projection of the intersection points of these clouds, designating them as potential earthquake zones. Research from the 1970s in China confirmed Lü's hypotheses. Lü also posited that these earthquake clouds could correspond to both recent and long-term seismic activities, as well as nearby and distant earthquakes. For instance, the 8.0 magnitude earthquake in Mexico across the Pacific and the Azores earthquake in the western hemisphere both affected the atmosphere over Beijing, with some observers reporting unusual cloud changes days in advance.
In addition to the common band-shaped earthquake clouds, there are also radial clouds that radiate from a point outward. These clouds typically appear in the morning and evening and can display various colors due to sunlight. The center of radiation often lies directly above the epicenter, making it difficult to see the full structure from nearby areas, where only converging finger-like clouds are visible. This type of cloud may primarily relate to nearby earthquakes.
Another type of cloud, referred to as rib-like clouds by seismologists, resembles neatly arranged ribs and spreads in a wide band in one direction. It may be a 'broadening' of serpentine clouds, likely resulting from two earthquakes occurring simultaneously from roughly the same direction.
How are earthquake clouds formed?
Japan is one of the countries with the most documented cases of earthquake clouds, leading Japanese scholars to be at the forefront of their explanation.
Associate Professor Makoto Manago from Kyushu University believes that prior to an earthquake, massive energy accumulates within the Earth, raising geothermal temperatures and heating the air, which creates rising air currents that spread in concentric circles to form elongated earthquake clouds at an altitude of around 1,000 meters.
However, there are aspects of Manago's theory that are difficult to substantiate. Chinese meteorological and seismological researchers have raised doubts from an atmospheric physics perspective.
Firstly, the stratosphere lies above the troposphere at an altitude of over 10,000 meters, a height that generally rising air currents cannot reach. Even volcanic eruptions or nuclear explosions can only create convection near the top of the troposphere. Such strong convection typically results in vertical development of clouds, such as tower-like, columnar, or mushroom-shaped clouds, rather than horizontally spread elongated clouds, and it does not explain why these elongated clouds align vertically with the direction of the seismic source.
Secondly, according to Manago's theory, earthquake clouds should appear directly above the epicenter. In contrast, according to Chinese atmospheric physicist Gu Zhenchao, earthquake clouds should not be more than 3,000 meters from the epicenter. However, reports indicate that people have observed earthquake clouds thousands of kilometers away from the epicenter, and some even claim to have seen them from halfway around the world. How can this be explained?
Thirdly, the thermal conductivity of Earth's rocks is extremely slow; it takes at least three years for energy to travel through 10 meters of rock. What mechanism, then, heats the atmosphere with the energy accumulated inside the Earth?
In response to the challenges faced by Manago's theory, Chinese scholar Lü Dajiong proposed the following explanatory theory: he believes that earthquake clouds may not only appear directly above the epicenter but also above fault zones far from the epicenter where stress is concentrated. When these already stressed faults are subjected to additional stress transmitted from a distant epicenter due to pre-earthquake volume expansion, the stress becomes even more concentrated. The strong stress on the fault causes rocks to compress and generate heat, allowing underground thermal currents to escape through the fault and rise to the atmosphere, forming band-shaped earthquake clouds.
Lü Dajiong also suggests that heat transfer from the Earth's interior to the atmosphere may not only occur through escaping air currents from the fault but can also happen through radiation (such as ultra-high frequency or infrared radiation) that heats various particles above the fault, leading to the formation of band-shaped earthquake clouds. Since faults are mostly aligned vertically with the direction of seismic wave transmission from the epicenter, the resulting band-shaped earthquake clouds also align with the vertical direction of the seismic wave transmission.
How are radial earthquake clouds formed? Lü Dajiong believes they arise from fault intersections where stress is highly concentrated, and since stress diminishes with distance, this results in radial earthquake clouds corresponding to the epicenter.
While Lü Dajiong's theories better explain certain characteristics of earthquake clouds, they remain speculative and lack empirical data. Furthermore, the ability of earthquake clouds from distant earthquakes to transmit stress remains questionable. The occurrence of earthquakes on the seabed raises further doubts about their potential to cause earthquake clouds.
Do earthquake clouds truly exist? How are they formed? These questions remain difficult to answer accurately.
