Statistical Evaluation of Efficiency and Possibility of Earthquake Predictions with Gravity Field Variation and its Analytic Signal in Western China

Abstract

This paper aimed at assessing gravity variations as precursors for earthquake prediction in the Tibet (Xizang)-QinghaiXinjiang-Sichuan Region, western China. We here take a statistical approach to evaluate efficiency and possibility of earthquake prediction. We used the most recent spatiotemporal gravity field variation datasets of 2002-2008 for the region that were provided by the Crustal Movement Observation Network of China (CMONC). The datasets were space sparse and time discrete. In 2007-2010, 13 earthquakes ([M s 6.0) occurred in the region. The observed gravity variations have a statistical correlation with the occurrence of these earthquakes through the Molchan error diagram tests that lead to alarms over a good fraction of space-time.The results show that the prediction efficiency of amplitude of analytic signal of gravity variations is better than seismicity rate model and THD and absolute value of gravity variation, implying that gravity variations before earthquake may include precursory information of future large earthquakes.

Critical zone of the branching crack model for earthquakes: Inherent randomness, earthquake predictability, and precursor modelling

“…Zhuang et al [61,62] used this model and a similar discrete version to model the explanatory effect of the observed data from the ultra-low frequency components of underground electric signals at 4 stations in the vicinity of Beijing in forecasting the occurrence of events with M ≥ 4 within a 300 km circle centred on Beijing, and showed that the explanatory effect is highly significant. The probability gain is about 2 -10, similar to the values obtained by Wang et al [48], Chen et al [5], and Han et al [14].…”

“…For example, the crustal strain estimated from surface displacement data is closely related to the crustal stress change. Changes in the gravity field provide us with information about the vertical motion of the crustal medium (e.g., [5]). There are also many reports on the radiative signals related to the changes in geo-electromagnetic fields, coseismically (e.g., [16,17,36,37]) or preseismically (e.g., [7,11,12,14,61]).…”

“…Here, we refer to Figure 5 for the usage of these two types of curves. Wang et al [48] validated the precursory information in GPS displacement data in the Taupo region, the California region, and the Kanto region, Chen et al [5] verified the explanatory effect of gravity anomalies for the occurrences of large earthquakes in western China, and Han et al [14] checked the signals of short-term anomalies in geomagnetic observations, all using the Molchan error diagram. To deal with positiveonly predictions, for example, the reverse tracing precursors [40], a gambling score is developed for such a purpose ( [54,56,58]).…”

“…That is to say, there possibly exists a limit to the prediction powers of such precursors. The current probability gains estimated from the GPS displacement data by Wang et al [48], gravity data by Han et al [5], and geo-electromagnetic signals by Han et al [14] all approximate a value of 3. Finding precursors with high probability gains as well as developing models and methods for combining different precursors are desired to obtain forecasts with higher probability gains.…”

Previous, Current, and Future Trends in Research into Earthquake Precursors in Geofluids

“…Automatic instrumental measurements of a variety of parameters, using advanced technology [68] were carried out. At present the Chinese monitoring network for the monitoring of earthquake precursors include GPS stations, magnetotelluric stations [69,70], and microgravimetric stations [71,72]. In particular, a network for groundwaters and gas monitoring was also set up in China.…”