User:Dirtyterp/1975 Haicheng earthquake

General Information
On February 4, 1975, an Ms magnitude 7.5 earthquake hit the city of Haicheng, Liaoning, China at 19:36 CST. The earthquake's strong magnitude -- and high intensity at the epicenter which measured an 8.5 on the Modified Mercalli Intensity Scale (or MMI) -- paired with its close location to civilization caused a large amount of destruction to infrastructure and property. In addition to damage in the Liaoning Province of Haicheng and its surroundings, minor damage was also reported in Seoul, South Korea, and the earthquake was felt as far away as Primorsky Krai, Russia, and in Kyushu, Japan.The city of Haicheng was home approximately one million residents at the time of the earthquake, 2,000 of which were reported to be deceased and even more reported to be injured. However, there could have been a much larger casualty count if not for the successful prediction of the earthquake and evacuation of the city.

The 1975 Haicheng Earthquake is one of the few earthquakes to ever be successfully predicted. Early in the morning of February 4, 1975, Chinese officials ordered that the city of Haicheng be evacuated, believing there to be a high likelihood of an earthquake occurring. The prediction was based on reports of changes in groundwater and soil elevations over the past several months as well as widespread accounts of unusual animal behavior, among other phenomena. This prediction was later put under heavy scrutiny and was deemed as a fluke when another earthquake hit the city of Tangshan in 1976 and was not predicted successfully causing an extreme amount of death and destruction to the area. This occurred only a year after Haicheng's successful earthquake prediction and evacuation. S

Damages
The city of Haicheng was decimated by this earthquake as the shaking was too great for the buildings to withstand. There was mass building collapse throughout the area as well as the destruction of cultivated land, roads, highways, and railways. It is approximated that 90% of the structures in Haicheng at the time experienced significant damage or were completely destroyed by the earthquake. Local bridges collapsed and oil transport pipelines were damaged. Unfortunately, due to the political climate in China at the time, exact damage totals are unknown.

However, damages were reported as far away as South Korea and Japan. Due to the distance between these areas and the epicenter of the quake, the damages were significantly fewer in number and lesser in degree. In Seoul, South Korea, the MMI was calculated to be a 4 in comparison to Haicheng where the MMI was determined to be 8.5. In contrast to mass building collapse in Haicheng, there were a few reports of smaller buildings collapsing partially as well as intense shaking of high rise buildings. Interruption of electrical service was also reported due to transformer tripping that is attributed to long-period seismic waves from the high magnitude earthquake being able to travel far distances.

Four-Stage Prediction Timeline
The prediction of the Haicheng earthquake was made possible by the tens of thousands of seismological and geophysical workers, as well as volunteers, that were a part of the People's Republic of China's National Earthquake Research Program which was less than ten years old at the time. Due to the political climate in China at the time, most information known to Americans has been compiled by the American Haicheng Earthquake Study Delegation that was sent to China by the United States a year after the earthquake occurred.

The Four-Stage Prediction Timeline is a term used to describe how the earthquake was predicted using precursory monitoring over time. As its name suggests, the timeline explains that prediction consisted of "four stages: long-term (a few years), middle-term (one to two years), short-term (a few months), and imminent (hours to a couple days)" (Wang et. al.). Long-term to short-term monitoring helped the National Earthquake Research Program at the People's Republic of China refine earthquake prediction gradually, aiding them in their overall successful prediction of the earthquake. The final "imminent" earthquake prediction was made when a series of foreshocks struck the area, which was deemed to be the most important precursor to the successful prediction of the earthquake. Due to these foreshocks, some of the final evacuation orders were given only hours before the destructive earthquake preventing further loss of life.

This prediction and evacuation saved countless lives, limiting the total fatalities to under 2,500 and total injuries to 27,500 people. The estimated number of injured and deceased individuals without the implementation of the evacuation skyrockets: estimating that over 150,000 people could have been injured without a successful evacuation. This estimation was further solidified when the following year, another high magnitude earthquake struck the nearby city of Tangshan. The Tangshan earthquake in 1976 was not successfully predicted and no citizens were evacuated. The total fatalities and injuries in comparison to those of Haicheng are extremely high; with the Tangshan earthquake causing over 200,000 fatalities and 160,000 injuries.

Long-term Prediction: 1970
After the occurrence of a number if large earthquakes from 1966 - 1969, a meeting was held nationally to discuss the where the largest seismic danger was in the People's Republic of China. These large earthquakes were determined to be moving to the North East. It was also discussed that there would be a large earthquake of magnitude 5-6 at least along the Pohai Gulf. The prominent faults in the area determined to be the danger were the Jinzhou, Zhuanghe, and Yalu River faults, which were all prominent North-Northeast striking faults. There was then a large increase in scientific investigation in the surrounding province of Liaoning, as well as many new seismic stations, due to this prediction.

Middle-term Prediction: July 1974
After four years of data collection the meeting was brought back together to determine a new prediction. They believed that the magnitude 5-6 earthquake they had predicted in 1970 would now occur within the next 2 years in the northern part of the Pohai Gulf. Severely increased microearthquake activity as well as levelling and short level lines data assisted in the new prediction decision. The scientific examinations in the area were increased significantly and a large education campaign was initiated to inform the public on earthquake safety and the hazards of earthquakes.

Short-term Prediction: December 1974
There was a series of earthquakes in the area of Liaoyang, an area of usually low seismicity, the larges of which had a magnitude of 4.8. These quakes prompted the Revolutionary Committee of the Liaoning Province to issue alerts of a possible large earthquake in the near future. Reports of odd animal behavior and changes in ground water levels increased in the area into 1975.

Imminent Prediction (Foreshocks): January-February 1975
The prediction was further updated to be a magnitude 5.5-6 earthquake in the first half of 1975, likely due to the series of quakes at the end of 1974 as well as the observations of animals and groundwater. The foreshocks of the Haicheng earthquake then began on February 1, 1975 and continued into February 3. There were foreshocks of magnitudes greater than 4, which were felt throughout the province. The reports of odd behavior of water wells and animals began to migrate towards Haicheng at this time as well. Anomalies of radon emissions, electrical resistivity, and a tilt anomaly also occurred. All of this data led to the conclusion that the earthquake would occur within the next two days. Emergency measures were then taken to prevent loss of life.

Natural Anomalies Influencing Earthquake Prediction
The study of declassified Chinese documents as well as interviews with witnesses have revealed the other occurrences considered by the People's Republic of China's National Earthquake Research Program when predicting the Haicheng earthquake. While these anomalies are not always indicators of a major earthquake to occur, they were all taken into account during the prediction of the Haicheng earthquake. These anomalies include ground surface deformation, changes in groundwater (including changes in level, color, and chemistry), and unusual animal behavior.

Ground Surface Deformation
Ground surface deformation, also known as geodetic deformation, occurred both before and after the Haicheng earthquake. Dating back to decades before the earthquake, geodetic deformation was observed in the form of vertical crustal movements in a broad area around the general region of where the earthquake struck in 1975. The epicenter of the earthquake happened to fall where two of these steep vertical crusts intersect.

Another instance of ground surface deformation that was taken into account when predicting the earthquake was data recorded by the Jin Xian station 18 months before the quake occurred that was located only 200 kilometers from the epicenter of the earthquake. This data encompassed many stages of crustal deformation. This began with recording the initial, stable state, of the ground surface in the area. Tilting of the ground in one direction was then recorded, following by the recording of the ground tilting in the opposite direction. Stages of rapid to slow tilting were also observed. These data sets provided basis for intermediate and short-term predictions for the Haicheng earthquake.

Changes in Groundwater
Numerous accounts of great fluctuations in groundwater levels measured both before and after the quake lead scientists to believe that these changes occurred due to tectonic activity. Before the earthquake, reports of major well water level inconsistencies by the general public increased greatly; as did reports of varying color, smell, and flow. Also of note, radon anomalies and other compositional differences were detected by numerous geological observatories while studying the earthquake.

Unusual Animal Behavior
Another believed sign of the earthquake coming was the unusual animal behavior. In December 1974, it was reported that rats and snakes appeared "frozen" on the roads. Starting in February 1975 reports of this type increased greatly. Cows and horses looked restless and agitated. Rats appeared "drunk", chickens refused to enter their coops and geese frequently took to flight. However, this prediction method remains a mystery to scientists. According to the USGS, reliable and consistent information about animal behavior being an indicator for earthquakes is elusive, as is a mechanism explaining how animals would be able to sense that an earthquake is coming. Therefore, for the time being, it is best to assume that animal behavior is not a reliable indicator of earthquake prediction.

Earthquake Prediction Scrutiny
In recent years, the success of the earthquake's prediction has come under scrutiny. Seismologists have agreed that the Haicheng earthquake can't be looked to as any sort of "prototype" for predicting future earthquakes, as the foreshocks that played a huge role in leading to prediction of this earthquake are not a regular, reliable occurrence before all earthquakes. However, Qi-Fu Chen, a research professor at Beijing's China Earthquake Administration, explained that this earthquake at least "showed the importance of public education," prompting a further discussion about the necessity of making the public aware of the dangers, preparations, and warning signs related to earthquakes.

It is still a topic of debate however whether there is any merit whatsoever of the prediction. Until recently, there were no details given of the evacuation which led to many scientist questioning the success of the prediction. The suspicion began were a lack of written records but increased due to the time period being during the cultural revolution, which was a period where gaining accurate information from China was extremely difficult.

This prediction was further scrutinized when another earthquake hit the nearby city of Tangshan only a year after the Haicheng earthquake was successfully predicted and evacuated. The 1976 Tangshan earthquake was not predicted by Chinese officials, and devastated the area resulting in many casualties. This earthquake failed to be predicted, and none of the foreshocks or other phenomena which were present before the Haicheng earthquake were observed prior to this incident. This second earthquake showed that the prediction of Haicheng's earthquake and subsequent evacuation was likely a fluke incident.

Evacuation
Before the earthquake occurred, a low-level alert was issued to the public, triggered by regional increases in seismicity (later recognized as foreshocks). However after foreshocks began to increase, both authorities and citizens were finally placed on high alert and an evacuation order was issued. Though this particular prediction of the earthquake was initially believed to be just the latest in a recent string of false alarms that had occurred in the preceding months, including one case of an earthquake swarm being caused by the filling of a reservoir, the evacuation of Haicheng proceeded anyway and saved countless lives.

The evacuation, despite successfully removing most of Haicheng's population, did not prevent deaths in its entirety. When the main quake struck at 7:36pm local time, a reported 2,041 people died. Over 27,000 people were injured and thousands of buildings collapsed. However, the death toll was much lower than the estimated 150,000 deaths which were believed to have resulted if the evacuation had not taken place. This earthquake prediction and evacuation of a potentially affected population, meaning it occurred before the earthquake hit, was the first in history.

Tectonic Setting
Understanding the tectonic setting in China was vital to the prediction of the earthquake.There were multiple large earthquakes that occurred in the three years prior to the 1975 Haicheng earthquake that took place due to right-lateral motion of North-Northeast trending strike-slip faults, which appeared to have migrated from Southwest to Northeast. The three earthquakes measured at magnitude of M6.8 in the Xingtai area in March 1966, M6.7 in the Hejian area in 1967, and M7.4 that is known as the Bohai Sea earthquake of 1969. These interpretations are believed to be tied into the Geomechanics Theory discovered by Li Siguang that explains how rocks stress as well as how and when faults will develop.