Abstract
Tsunami occurrence has created havoc for humans. This unfortunate event however does provide some pre-alert signals which if carefully analyzed can help in pre-sensing this havoc. The signals can be in form of certain indicators in environment and in nature which can be sensed dynamically. Various studies have reported cases of animal behavioral signals prior to tsunami. These changes are a result of environmental changes before any such event occurrence. This paper proposes a confident fuzzified system derived over marine behavior to predict tsunamis (3CC
Introduction
In 2004, huge underwater seismic waves commonly termed as tsunami was witnessed along the coast of Sumatra.
Since then various actions have been taken up by government institutions as well as research community to develop efficient solutions needed, where such seismic waves can be pre-sensed such to help saving human lives [1]. However, the reoccurrence of similar instances where no alerts were generated for abandoning the affected areas timely have raised concerns over the efficacy of such solutions. Here, the solutions referred to as what is commonly termed as Tsunami warning system (TWS). As per certain recent news articles, these TWS have somehow not been able to generate any timely alerts while they were designed for the same.
As per human experiences, certain gaps [2, 3] have been identified with respect to these TWS which can and have served as action points for the scientific community for improvement:
The remote areas along the coastlines usually do not receive timely warning sirens. Various local inhabitants are expected to monitor the coastline despite the presence of TWS. From 2, the inefficacy of inhabitants in identifying or categorizing alarming situations might lead to false positives or false negatives in timely predicting mishaps.
Given these pitfalls or gaps which were identified from past instances of tsunami occurrence, a need to design and implement effective as well as efficient warning systems became inevitable [4]. Seismic waves give pre occurrence signals by both means i.e. geophysical as well as by nature. Natural precursors include the aquatic lives which do get affected by these underwater seismic waves. Any changes in their adapted environmental conditions make them behave anomalously. Such observations have been studied and reported by the research community as well as the affected population [5, 6, 7, 8].
The current tsunami prediction systems are monitoring the geophysical conditions more than the natural responses. The geophysical responses that are being tapped mainly are earthquake magnitude, underwater bottom layer pressure, changed in tidal activities, waveform properties [9, 10]. The sensor nodes that record these changes are deployed underwater for precise information capturing. We propose a 3 class classification model with a confident overlap based fuzzified algorithm based out of aquatic species change in behavior here: Sea turtle and earthworm both.
Marine life, can act as timely predictor to sense tsunami.
The research community has believed that aquatic animals do produce certain messages or signals in terms of behavioral responses which can act as predictive means to generate alerts [11]. Here, Apart from just generating signals in form of responses an integrated system where these responses are collected and analyzed together for generating awareness [12]; these messages if integrated to the current warning systems can help in generating an effective design and diverse warning system.
In existing state-of-art no global warning system produces aquatic animal behavioral alerts in concatenation to geo physical changes in environment. If analyzed well in time, the efficacy of existing TWS can be enhanced.
The specific contributions of this article are as follows.
An exhaustive categorization of existing TWS or existing techniques in literature has been presented. This has underlined the dire need of a special hybrid systems marking higher efficiency for timely prediction
Based on above observation, a hybrid prediction model (3CC
The hybrid model uses novel quantified anomalous sea animals (Turtles and Earthworms) behavioral attributes obtained in response to changing environmental condition and performs a 3 class classification using fuzzified rule based extraction
The derived rules obtained using rated confident and overlap scores are classified into 3 different classes as tsunami-alert, tsunami-pre-Alert and tsunami-no-alert years. Here the classification is done on the basis of confident overlap function scoring. The resulting insights match with the historical data; again identifying year 2004 as an alert year.
In this paper, a confident overlap function based algorithm (COV_FMB) is proposed and implemented. This algorithm gives fuzzified linguistic rules evaluated from aquatic animal behavioral attributes. The 3 class classification here is defined as: Pre-Alert, No-Alert and Alert. 2004 being the known tsunami year, from this algorithm also comes to be the tsunami year as well. To evaluate these rules, confidence score is also calculated for each rule where the optimization of these rules is highlighted. Two datasets used here are from a public source which gives behavioral activities of Earthworms and sea turtles.
Tsunami warning system categorization
Earthquakes, landslides, volcanic eruptions all can lead to tsunami generation. In this section different categories of TWS have been discussed, describing about existing and proposed algorithm as well products
Tsunami is a hazard that is generated by short period underwater perturbations [13, 14]. They can also be a result of ongoing volcanic eruptions or landslides or repetitive earthquakes. Based on the time period that it takes to propagate, tsunamis are categorized as either “ongoing” or “slowly creeping”. The warning systems so designed generate alerts using different types of sensed parameters. From the different types parameters sensed, the current state of warning systems is being categorized into two: Geophysical systems and People oriented systems. Consequently, a hybrid system is further proposed, where both features can drive seismic alerts based on response of one from the other.
Warning systems based on geophysical features
Seismic perturbations can cause changes in environment conditions for egg: pressure underwater, tidal wave activity of waves, sea-level, and height of waves, temperature and salinity of the water [15, 16]. As noted, these are all geo-physical features on which a TWS can be designed. The predictors used here show changes which are time dependent. For timely alerts quick changes needs to be tapped for getting an efficient warning system.
People based TWS
Community or people-reaction derived warning systems are designed to generate alerts using an individual observation that includes coastline fisherman, local inhabitants near sea shores etc. It’s a response based model where the word of mouth further propagated can help in a timely evacuation. The analysis here is carried out on behavioral responses of humans towards the change in geophysical changes happening in the environment. These responses could also be there deep observations towards changes they are able to identify in natural elements like underwater animals and plants. Various content and people behavioral based warning models and studies have been discussed in [20].
Nature derived warning systems
Underwater animals as well as plants are inherently adapted to a stable and suitable environment as per the conditions they are subjected to [17]. Any inconsistency or deviation in the environmental conditions can lead to changes in feeding, locomotion, migration as well as positioning patterns of these creatures. Seismicity can lead to unwanted disturbances in the environment [18]. Hence Marine life in specific does get affected by any change in the adaptive environment they are already a part of. These changes have been observed sometimes days, month or months before the actual occurrence of this unfortunate event: Tsunami. Several researchers have highlighted such facts. One of the examples is the changes in behavior of a common toad much before the waves hit the Ruffino Lake in 2009 [19].
Hybrid systems
This paper therefore proposes an additional category of warning system which is an integrated solution. The proposed system is a hybrid of both the natural and geophysical parameters identified individually in the previous sections. Figure 1 presents an architecture block diagram of the hybrid system defined 3CC
3CC
A similar responsive association between behavior of sea species and geo-physical conditions was observed when 6 days before 2011 tsunami in Japan [18], a large amount of whales were found dead along the coastline. Similar instance of beaching was observed in New Zealand in 2015 [21]. Such incidents were based out of the inability of sea animals to adapt to the diversely changing environmental conditions. Hence, a responsive reaction by these animals can be sensed, pre-analyzed and an alert much before the occurrence of the event can be generated which will help in timely evacuation. It was also reported that in above mentioned instances the species who suffered from this “mass suicide” did not have any other disease. Hence, the architecture in Fig. 1 shows a relational link between the two parameters.
Here, the parameters sensed are the change in electromagnetic force (EMF), its effect on sea turtle count (Cant) and Angle of Deviation (AOD) (monthly) as well as OD (Daily).
These parameters cover the impact of tsunami on both breeding and migration activities of these underwater species as discussed in [22].
The need of a hybrid system deriving alerts on bio system responses followed by geophysical changes has been highlighted in the previous section. The motivation behind such proposition is that tsunamis still are going undetected timely. From the examples cited, it is possible for such hybrid warning systems to generate alerts at least few to many days before the actual onset of such event. Any change in adaptive conditions such as electromagnetic field affects migration and locomotion pattern of underwater species. Such as sea turtles which use their inherent magnetic cues for finding direction to locate food or prey underwater. As any change leads to a complete deviation which therefore makes them food deprived causing a reduction in underwater count.
Here, on the basis of existing evidences and [23, 24, 25] reports that identify how electro-magnetic fields can affect the behavior of marine animals. Based on the effects of the changed electromagnetic field, the consequent changes in the behavior of aquatic species can be used one of the precursors in generating alerts [26]. Thus, the proposed system works by formulating new dimension to tsunami prediction on the basis of Sea Turtle and Earthworm behavioral patterns. Sea turtles have been used a case of study in respect to the results of an experiment conducted in [27]. Here, the turtles that were exposed to strong magnetic fields from north deviated to south direction giving a change in locomotion. Similar observations are highlighted for Earthworm behavior in [40].
Three class classification using fuzzy rules
Multiclass classification differs from binary classification to the number of output class. Here the given set of predictor attributes are used to map it with a finite set of categories (classes), i.e., each input is classified into one of the possible target class [27, 28]. Multiple classes are considered simultaneously, it is complex than the binary classification where there are only two classes involved [29].
Usually classification as a concept is used as an initial step where the similar members of a group are always grouped together. Such preliminary analysis helps in obtaining a pattern detection scheme where a trend or a particular incoming instance based classification can be performed. In order to devise an algorithm for making a precise classification, learning the trajectories of data is needed. Various learning models have been used and proposed in past. Here, combination of classifiers has also been explored to obtain highly correlated results and maximized inter cluster (group) distance.
The methodology used by different classifiers is based on the representation of the input pattern as well as the measurement or the classifying criteria. For example: Kitler et al. in [30] have used a joint probability distribution based sum rule combination to classify the data. The criteria used here is a cost minimizing function to minimize the error obtained from above sum combination. Followed by above is a Naïve Bayes classifier [31] uses a conditionally independent probability for data analysis.
In probability concept, the classification rules are derived from the basic premise B (say) is objectively or subjectively estimated to be true. However, these classifications suffer from computational limitation when the input data comes out to be uncertain and dynamic [32].
Hence, fuzzy set theory introduced in [33, 34] served as a mathematical foundation for modeling imprecise data. Various researchers in past have used this theory to model behavioral data to deal with inexactness or fuzziness of such data. Here a defined cluster analysis is performed to take in the vagueness of data through degrees of membership functions in form IF-THEN-ELSE decision rules. These rules are computed to be human readable.
Dataset description
The proposed COV_FMB algorithm works on two data sets prepared. One is obtained from Reunion Island near Indian Ocean coasts containing marine turtle behavioral statistics termed here as D1 [35]. Second is the same year window dataset (D2) [36, 40] for Earthworm activity near coastlines of Indian ocean.
Following parameters are extracted from both data-sets in form of attribute for particular specie [37, 38].
Deviation in angle of motion (between consecutive months) as AOD(M). For every year in the complete dataset D1 and D2 both, this parameter is formulated between each pair of months occurring consecutively. These parameters are partitioned under linguistic labels as shown in Table 1. Deviation in angle of motion (for existing values in both datasets separately) formulated between each pair of months occurring consecutively. This is calculated for each year in the whole dataset. The above parameters are calculated using tapped longitude and latitude values for both datasets where deviation was calculated using haversine equations as shown in [41]. Underwater specie count (as turtle and earthworms both). Electromagnetic Field: Due to seismic activity, the adaptive electromagnetic field starts varying. during underwater seismic perturbations gets changed. From the existing dataset (both D1 and D2) a SQL query command is used to extract behavioral activity for a repeated timestamp. These changes in attributes are linguistically mapped as shown in Table 1. From the above process, there were some values missing for a particular timestamp for different attributes. The missing values of the attributed dataset also had values for days closer to 2004. This we assume to be a cause of unavailability or inability of sensors to track the information in advance to occurrence of such hazardous event or probably due to unwanted catastrophic failures, therefore it is one of the limitations here.
Table 1 represents the parameter description with value description for each variable as Low (L),Medium (M), High (H), Very High (VH) for both D1 and D2.
Linguistic label characterization of both datasets






