Tsunami Warnings: Understanding in Hawai‘i 1

This manuscript has been accepted for publication by Springer, Natural Hazards. It is scheduled to appear in print in mid-2006. Tsunami Warnings: Understanding in Hawai‘i CHRIS E. GREGG* Department of Physics, Astronomy and Geology, East Tennessee State University, Box 70652, Johnson City, TN 37614, USA and Department of Geology and Geophysics, University of Hawai‘i, 1680 East-West Road, Honolulu, HI 96822, USA BRUCE F. HOUGHTON Department of Geology and Geophysics, University of Hawai‘i, 1680 East-West Road, POST 617c, Honolulu, HI 96822, USA, E-mail (bhought@soest.hawaii.edu) DOUGLAS PATON University of Tasmania, School of Psychology, Bag 1-342, Launceston, Tasmania, Australia, E-mail (Douglas.Paton@utas.edu.au) DAVID M. JOHNSTON Institute of Geological and Nuclear Sciences, 69 Gracefield Road, New Zealand, E-mail (D.Johnston@gns.cri.nz) DONALD A. SWANSON U.S. Geological Survey, Hawaiian Volcano Observatory, P.O. Box 51, Hawai‘i National Park, HI 96718, USA, E-mail (donswan@usgs.gov) BRIAN S. YANAGI

International Tsunami Information Center, 737 Bishop Street, Suite 2200, Honolulu, HI 96813, USA, E-mail (Brian.Yanagi@noaa.gov) *Corresponding author telephone (423) 439-7526; fax (423) 439-6905; E-mail gregg@etsu.edu and cgregg@soest.hawaii.edu

Abstract. The devastating southeast Asian tsunami of December 26, 2004 has brought home the destructive consequences of coastal hazards in an absence of effective warning systems. Since the 1946 tsunami that destroyed much of Hilo, Hawai‘i, a network of pole mounted sirens has been used to provide an early public alert of future tsunamis. However, studies in the 1960s showed that understanding of the meaning of siren soundings was very low and that ambiguity in understanding had contributed to fatalities in the 1960 tsunami that again destroyed much of Hilo. The Hawaiian public has since been exposed to monthly tests of the sirens for more than 25 years and descriptions of the system have been widely published in telephone books for at least 45 years. However, currently there remains some uncertainty in the level of public understanding of the sirens and their implications for behavioral response. Here we show from recent surveys of Hawai‘i residents that awareness of the siren tests and test frequency is high, but these factors do not equate with increased understanding of the meaning of the siren, which remains disturbingly low (13%). Furthermore, the length of time people have lived in Hawai‘i is not correlated systematically with understanding of the meaning of the sirens.

An additional issue is that warning times for tsunamis generated locally in Hawai‘i will be of the order of minutes to tens of minutes and limit the immediate utility of the sirens. Natural warning signs of such tsunamis may provide the earliest warning to residents. Analysis of a survey subgroup from Hilo suggests that awareness of natural

Tsunami Warnings: Understanding in Hawai‘i 2

signs is only moderate, and a majority may expect notification via alerts provided by official sources. We conclude that a major change is needed in tsunami education, even in Hawai‘i, to increase public understanding of, and effective response to, both future official alerts and natural warning signs of future tsunamis. Key words: tsunamis, alerts, warning system, sirens, natural warning signs, Hawai‘i

1. Introduction

The Hawaiian Islands in the north-central Pacific Ocean are at risk from a wide range of natural and manmade hazards (Fletcher et al., 2002; Hamnett et al., 1996). Tsunamis represent a major threat in terms of the safety of people and property because populations and infrastructure are densest in the coastal zone where tsunami risk is greatest. An effective tsunami warning system is essential in Hawai‘i.

The earthquake and tsunamis on December 26, 2004 in southeast Asia, which claimed 176,260 lives with an additional 49,682 still missing (Miller, 2005), illustrated three important points with regard to tsunami warnings and response. First, that the warning times for local tsunamis are so short that vulnerable communities must react (seek shelter) to the ‘natural warnings’ of tsunamis provided by ground motion, unusual sounds, sea level changes, changes in wave forms, or animal behavior. Second, in distant communities the distinction between incurring and avoiding significant loss of life is a system for transmitting effective warning messages from public officials to the communities. Third, natural warnings have the potential to provide an effective alert of tsunamis in distant areas when no official warning system exists.

A history of both local and distant tsunamis in Hawai‘i means that travel times will vary from minutes to hours, respectively (Zetler, 1947). Hawaii’s people must therefore be prepared to respond to two very different time scales for threats. Effective public responses to these threats require a warning system that meets the demands of both time scales for emergencies. The current tsunami warning system in Hawai‘i is linked to a network of sirens that is sounded when a tsunami warning is issued (Hawaii State Civil Defense, 2004b). However, public understanding of the sirens and natural warning signs of tsunami has not been evaluated, and so current levels of public awareness of, and preparedness to respond to, these warning mechanisms are therefore unknown.

1.1. HAWAI‘I

Hawai‘i has 1.2 million residents and 6.4 million visitors annually (State of Hawaii, 2002). Most development that supports this population lies along narrow stretches of coastal terrace, both near and within tsunami inundation zones. For example, Raine (1995) reported that over 60,000 people on O‘ahu lived within tsunami evacuation zones in 1995 and that many more worked and sought recreation in these zones. Most of this development has occurred since the last large scale, significantly damaging tsunami in 1960, so people have little direct experience with the hazard, the sirens, and natural signs of tsunamis. Furthermore, tsunami evacuation zones for Hawai‘i (Curtis, 1991) may be inadequate to protect the at-risk populations from large destructive tsunamis such as, but not limited to, the events of December 26, 2004. However, these 1-dimensional maps are being updated with improved 2-dimensional maps (Gonzalez et al., 2005).

Tsunami Warnings: Understanding in Hawai‘i 3

1.2. TSUNAMIS IN HAWAI‘I

Lander and Lockridge (1989) reported that 26 damaging tsunamis have occurred in the Hawaiian Islands since A.D. 1819 (i.e., waves with run up heights of >1 m), with the most recent deadly and devastating local and distant tsunamis occurring in 1975 and 1960, respectively (Cox and Mink, 1963; Eaton et al., 1961; Lachman et al., 1961; Lander and Lockridge, 1989). All but four of these tsunamis were from distant sources.

1.3 NATURAL WARNING SIGNS OF TSUNAMIS

Natural warning signs of tsunamis broadly include ground motion (i.e., shaking) from earthquakes, unusual sea-level fluctuations and unusual wave forms (Darienzo et al., 2005; Dudley and Lee, 1998; Gonzalez, 1999). They also include various sounds that have been described as thunder, thunder-bolts, locomotives, helicopters and booms (Gonzalez, 1999; Shuto, 1997), as well as unusual patterns of animal behavior such as that described in the events of December 2004 in southeast Asia. However, all of these signs may not occur or be identical in every tsunami event. Furthermore, natural signs of tsunamis have their limitations as warning mechanisms. For example, ground shaking from a tsunamigenic earthquake may not be felt for a variety of reasons. The occurrence of tsunamis at night when people are generally asleep may further limit the utility of sea level fluctuations, wave forms and sounds to serve as effective alerts of tsunamis.

The behavior of tsunamis in coastal waters is complex and varied (Gonzalez, 1999; Lander and Lockridge, 1989). For example, small changes in bathymetry and the shape of the coastline affect the behavior of tsunamis at the shore (Loomis, 1966). Tsunamis may evolve on shore as a breaking wave, as a wall of water, or as a tide-like flood (Gonzalez, 1999). Furthermore, the leading waves of tsunamis can arrive as a trough or a crest, and this will determine whether sea level first rises or lowers at the shore (Lander and Lockridge, 1989).

The diverse nature of natural warning signs of tsunamis poses challenges to providing useful information to the public. Furthermore, inconsistent and ambiguous information about these signs makes public education difficult and recommending specific behavioral responses problematic. For example, descriptions of how to make use of sea-level fluctuations and ground shaking during earthquakes as warning signs of tsunami are insufficiently specific to provide a clear action plan. Comparatively little information exists about the various sounds (Shuto, 1997) that have been linked to tsunamis, especially how to recognize and respond to these sounds.

The following are examples of existing information about sea level changes as natural signs of tsunamis. These phrases are sometimes offered as warning signs or signals to evacuate, but the extent to which they differ from ordinary sea conditions is seldom specific enough to be useful.

• “Rapid or gentle rising or falling of sea level” (Lander and Lockridge, 1989) • “A noticeable rapid rise or fall in coastal waters” (FEMA, 2003) • “Normally, a tsunami appears as a rapidly advancing or receding tide. In some

cases a bore (wall of water) or series of breaking waves may form” (NOAA, 2004)

• “A breaking wave, a wall of water, or a tide-like flood” (Gonzalez, 1999)

Tsunami Warnings: Understanding in Hawai‘i 4

• “Relatively gentle rise of water level, flooding of the shore, or a wave with steep front and much turbulence that strikes the shore with great violence. The withdrawal of water or the rise of water level” (Macdonald et al., 1983)

• “Rapid draw down or sudden rise” (Darienzo et al., 2005) The descriptions above highlight the variety of tsunami phenomena that may occur in coastal waters but they also show how descriptions are inconsistent. With regard to earthquakes, the intensity of ground shaking in any specific area is not fixed and will vary as a consequence of factors such as the magnitude of the earthquake, distance from the earthquake, geological and soil conditions, and presence or absence of engineering structures (e.g., shear walls), etc. Recommendations of how to make use of earthquakes and ground shaking as warning signs of tsunami are also inconsistent. For example, literature states:

• “A strong earthquake may cause tsunamis. Go to high ground immediately” (Official information provided in Hawai‘i telephone books).

• “Evacuate if there is strong, prolonged ground shaking” (Gonzalez, 1999). • “If on the beach or near the shoreline: If you feel a very strong earthquake,

evacuate to higher ground immediately” (NOAA, 2005) Collectively, the examples above highlight the need for greater consistency of official descriptions about natural signs of tsunamis and how people should respond to them. However, there is also a need to understand better the physical characteristics of tsunamis in shallow water and ground shaking from earthquakes as signs of imminent tsunami.

1.4 SOCIAL SCIENCE AND WARNINGS

The public’s response to warning messages is complicated by numerous factors (Lindell and Perry, 1992; Sorensen, 2000; Tierney et al., 1999). Mileti and O’Brien (1992) described the response to warnings as a sequence referred to as the “hear-confirm-understand-believe-personalize-respond” model of risk communication. This model describes how people shape their perceptions of risk and behavior sequentially following receipt of a warning. This process differs from person to person and is influenced by factors such as age, gender, or level of education. The rarity of warning events such as tsunamis also means that people often look to others to clarify what they see as an ambiguous situation (Latane and Darley, 1976).

In the 1960’s, two studies focused on awareness of the meaning of the siren system in Hawai‘i (Havighurst, 1967; Lachman et al., 1961). These showed that public understanding of the meaning of the siren was very low. In Hilo, about 5% understood the meaning of the siren in 1960 (Lachman et al., 1961). Most people associated the siren with arrival of a tsunami in 1960 (Johnston, 2003; Lachman et al., 1961), but at that time the siren actually meant “Alert” with no behavioral response connotation, so understanding was indeed low. On O‘ahu, about 8% could distinguish the enemy attack siren from the tsunami siren (Havighurst, 1967).

In a more recent study of western Hawai‘i (i.e., Kona), Gregg et al. (2004) reported a much higher level of understanding of the siren system. That study found however no correlation between understanding of the siren and awareness of key official information for disaster preparedness, printed in Hawai‘i telephone books (Verizon Hawaii, 2002). Gregg et al. (2004) suggested that familiarity with routine siren testing may help explain the observed levels of understanding there.

Tsunami Warnings: Understanding in Hawai‘i 5

1.5. SIREN WARNING SYSTEM

The sirens in Hawai‘i were installed as a network of pole-mounted sirens in populated coastal and inland areas in 1940 (J. Johnston, pers. comm, 2005). However, they were not used to alert the public to tsunamis until after the 1946 tsunami (Johnston, 2003). Historically, there have been frequent modifications to the siren system because of technical issues and changes in the philosophy of use. For example, at different stages, the tone, number and duration of siren soundings referred to specific hazard threats (e.g., tsunamis and air raid ‘alert’ and ‘take cover’). A siren signal specific to tsunamis existed between 1960 and 1966, but the signal was changed in 1967 to an Attention Alert Signal linked to all major emergencies. However, this excluded enemy attack, which retained a distinct signal. Between 1960 and 1967, researchers discussed the need for clarification of public response to the tsunami siren signal. For example, Cox and Mink (1963) reported that, “Some instructions indicate that the appropriate response [to the tsunami siren] is immediate evacuation, others, that the appropriate response is preparation for evacuation and checking with the radio for further instruction” (Anderson, 1967). The switch from a hazard specific tsunami siren signal to an Attention Alert Signal for multiple hazards meant people would need to tune to a radio station to receive information about the type of emergency occurring, such as tsunamis.

Currently there remains one siren tone the “Attention Alert Signal”, which is a steady 3-minute tone. The current siren system has been most commonly used for tsunamis and hurricanes and was last used to warn of a hurricane in 1992 and a tsunami in 1994.

Hawai‘i has 168 fully functional electronic sirens, 166 additional sirens that need further upgrading, and 167 areas with gaps in coverage (N. Ogasawara, pers. comm, 2004; Fig. 1). The network of sirens supplements the Federal Emergency Alert System, which disseminates messages over radio, television and cable television. Civil Defense messages, such as those to evacuate, also may be disseminated through police, fire department, civil defense, and civil air patrol aircraft. If sirens are sounded, messages informing the public about the reason for activation of sirens are activated (Hawaii State Civil Defense, 2004b).

Information relating to the siren has been available in Hawaiian telephone books since at least May 1960 and routine tests of the sirens have been conducted by Hawai‘i State Civil Defense since 1978. Prior to May 1960, it is unclear how siren information was disseminated to the public. During current tests of the siren, sirens are sounded for 30 seconds at 11:45 AM on the first workday of each month. There are no studies of the relationship between awareness of these tests and understanding of the meaning of the siren.

Despite the many sirens in Hawai‘i, some people may not hear the Attention Alert Signal. For example, in a study on O‘ahu, Raine (1995) found that 12% of surveyed respondents reported they either did not hear or could not remember if they heard the sirens sound during the 1994 tsunami warning issued in Hawai‘i. Another problem is that the signal may differ from published descriptions. While some sirens are stationary and provide a uniform tone, others rotate, causing the sound to resemble multiple tones or the wailing (rising and falling) tone used until recently to indicate enemy attack. This may lead to confusion in the interpretation of siren soundings. As ambiguity regarding interpretation of the warning increases, the greater is the likely delay in public response.

Tsunami Warnings: Understanding in Hawai‘i 6

Such ambiguity may contribute to increased use of telecommunications systems to seek further information (i.e., confirm and personalize the warning), which is a concern because it may clog the system and prevent the exchange of official information. This was a problem during a recent Tsunami Watch issued in September 2003 (J. LaDouce, pers. comm, 2004).

1.5.1 Current criteria for sounding sirens

If the threat of tsunamis is from a distant source, then sirens will not sound until a tsunami warning has been issued. In a tsunami warning, standard operating procedures of Civil Defense call for evacuation sirens to sound 3 h prior to arrival of the first wave on Hawai‘i’s shores, then again at 2 h, 1 h and 0.5 h prior to impact (Hawaii State Civil Defense, 2004b). However, this schedule is not widely known or publicized. If the threat is a local tsunami, sirens may be sounded immediately (Hawaii State Civil Defense, 2004b).

2. The Survey

2.1 METHODOLOGY

Surveys designed to assess public understanding of the sirens and the meaning attributed to siren soundings were conducted on the islands of Hawai‘i, Maui, O‘ahu and Kaua‘i in the state of Hawai‘i (Fig. 1 inset). The relationships between awareness of siren testing, test frequency, length of residency in Hawai‘i and understanding of the meaning of the siren were examined. The level of public awareness of natural warning signs of tsunami was examined in a subgroup in Hilo on the island of Hawai‘i where tsunamis have been most damaging (Fig. 1d). Survey questionnaires were distributed to middle-school students and to one of their parents or guardians (adults).

2.2 SAMPLE SIZE AND DEMOGRAPHICS

The total sample size is 956 (440 students and 516 adults). Twenty of these respondents did not respond to questions about the siren. The rate of return for questionnaires was 44% for students and 39% for adults. The mean age of the sample was 13 years (sd = 0.57) for students and 43 years (sd = 7.67) for adults. Gender, for students, was 39% male and 59% female. For adults, gender was 23% male and 75% female.

Hawaiian residents have a very diverse ethnic background. For example, the State of Hawai‘i had the highest percentage of people who reported more than one race in the latest US census (U. S. Census Bureau, 2000). The ethnicity of our sample is: Caucasian (17%), Asian (49%), Hawaiian, Part-Hawaiian or Pacific Islander (16%), other (4%) and multiple ethnicities (12%). On average, Caucasians and Asians are underrepresented in our sample by about 7%, Hawaiians by 6% and those selecting multiple ethnicities by about 10%. The percent claiming other ethnicities was equal to that reported in the census. Our data provide a good cross-section of all major ethnic groups in Hawai‘i.

Tsunami Warnings: Understanding in Hawai‘i 7

2.3 RESULTS

2.3.1 Awareness and Understanding of Sirens

The sirens have been operational and routinely tested for decades, so we anticipated that levels of awareness of the tests and test frequency would be high. Indeed, on average, over three-quarters of students (77%) and nearly all adults (92%) answered “yes” to a question asking if the sirens were tested (Table 1). An interesting finding was that the percentage of students who said the sirens were tested was highest in Hilo (92%) and decreased in the areas surveyed on Maui (77.2%), O‘ahu (73.4%) and Kaua‘i (68.2%). This reflects the extensive educational outreach regarding tsunami hazards and preparedness in the high-risk Hilo area compared with other islands where historical tsunamis have been less destructive and outreach less intensive. The trend was not observed among adults; awareness of the tests among parents was uniformly high (from 85.9% in Pāhoa to 95.4% in Hilo).

Awareness of the frequency with which the sirens are tested was high, with some 77% of respondents aware that the tests were conducted monthly (Table 2, 67% of students and 86% of adults). Awareness of the test frequency for students was again highest in Hilo (89.3%) and lowest in Kaua‘i (47.7%). Awareness in Maui was 64.1% and in O‘ahu it was 69.4%. In contrast, 97.7% of the adult respondents from Hilo were aware of the test frequency, as well as 85.9% from Pāhoa, 80.9% from Maui, 84.4% from O‘ahu, and 84.2% from Kaua‘i.

We anticipated that understanding of the siren would be commensurately high. To elicit people’s understanding of the meaning of the siren sounding and its implications for behavioral response in the current study, we asked an open-ended question ― “What does the Hawai‘i emergency alert system’s steady three-minute siren tone indicate?” Consistent with studies of the meaning of the in the 1960s (Havighurst, 1967; Lachman et al., 1961), understanding of the specific meaning of the siren was found to be very low. On average, correct student and adult responses were about 1% and 13%, respectively (Table 3). Most of the respondents indicated they did not know the meaning of the siren (i.e., 70% of students and 50% of adults).

The data in Table 3 suggest that understanding of the meaning of the Attention Alert Signal is very low, but some of the responses in the ‘other’ category of Table 3 could be considered partially correct (Attention Alert Signal, alert). However, they are less accurate than “tune to radio or television…” The following is a closer look at these ‘other’ responses. Percentages are given in terms of the total number of students (n = 432) and adults (n = 504). Some respondents associated the siren with the terms “emergency” (6% of adults and 3% of students), “warning” (5% of adults and 3% of students), and “attention alert” or “alert” (5% of adults and 2% of students). Other people interpreted the siren to mean a tsunami was possible or imminent, or as a tsunami warning (8% of adults and 9% of students). Fewer respondents (3% of adults and 8% of students) related the siren to hurricanes and even fewer to other hazards, although many students related the siren to the specific hazard under investigation in their respective survey. Several people related the siren to “enemy attack” or “war” (2% of adults and 1% of students), suggesting that old official siren definitions are still a part of modern cognition. Finally, a few respondents associated the siren with a test of the system (3%

Tsunami Warnings: Understanding in Hawai‘i 8

of adults and 2% of students), which has obvious implications for timely response to siren soundings.

2.3.2 Statistical Significance

We evaluated the effect of awareness of the siren tests and test frequency on interpretations of the meaning of the siren using results from the subgroup of 504 adults. Results are not reported for students because only 3 students were aware of the meaning of the siren. Responses to the question asking if the sirens were tested were condensed to two values (1 = yes and 2 = no or don’t know). Similarly, responses to a subsequent question asking about the frequency of the test were condensed to two values (1 = monthly and 2 = annually or don’t know). Responses to the question asking about the meaning of the siren were also condensed to two values (1 = tune to television/radio and 2 = don’t know or other).

On average, only 14% of the adults who knew the sirens were tested also knew the meaning of the sirens. However, in those respondents that did not know the sirens were tested, none knew the meaning of the siren (χ2 = 6.904, df = 1, p = 0.009). Similarly, using the subgroup of 462 adults that were aware that the siren was tested, only 15% of those who knew the frequency of the tests also knew the meaning of the siren.

The number of years that adult respondents indicated they had lived in Hawai‘i were condensed to 10-year increments. These data were analyzed against understanding of the meaning of the siren. Length of residency did not appear to systematically influence people’s understanding of the siren (Table 4). Understanding of the meaning of the siren peaked to 20% in those who had lived in Hawai‘i for 40-49 years. One possible reason for this is that those in the 40-49 years group would have been living in Hawai‘i during the devastating 1960 tsunami, and this may have made tsunami issues more salient.

2.3.3 Expectations of Tsunami Warning Signs (Hilo sub-sample)

Given the history of tsunami damage in Hilo, this area was selected to examine more closely awareness of natural warning signs for tsunami. The level of experience of tsunamis recorded by the adults in Hilo was low, with only 16% indicating that they had experienced a tsunami. Table 5 shows write-in responses from 78 students and 88 adults to the question, “What signs would alert you that a tsunami will occur?” The question was designed to elicit people’s awareness of natural warning signs of tsunami and expectations of the source of warnings in future tsunamis. That is, we were interested in knowing whether people anticipated that natural warning signs would alert them or if they believed alerts would come only from official sources, or some combination of these.

While many students and adults perceived that earthquakes or unusual sea level changes or fluctuations would occur, most people had the perception that an official notice would alert them (e.g., siren sounding, Civil Defense, police, etc). The data suggest that while many people recognize that there are natural signs of imminent tsunamis, there may be an expectance and dependence on government officials and agencies to provide them with an alert. The data from which Table 5 is compiled indicate that, not surprisingly, the responses regarding earthquakes and changes in sea level are highly variable. Responses associated with unusual sea-level changes included: “quickly

Tsunami Warnings: Understanding in Hawai‘i 9

receding tide”, “receding tide”, “calm or abnormal ocean”, “growing shoreline”, “high tide rising”, “tides and currents”, and “can see bottom of ocean”. Descriptions of wave forms included: “big waves”, “high waves”, “choppy waves”, “calm ocean”, and “abnormal ocean”. No respondents mentioned the sounds that have been linked to tsunamis or the wall of water that is often used to describe tsunami crests.

The finding that many people are aware that there are natural warning signs of tsunamis, regardless of how they describe them, is encouraging. A limitation of these data is that the accuracy with which people can link these phenomena to a tsunami event cannot be determined. Furthermore, the manner in which people would respond once they perceive the indicated sign or signs cannot be determined from these data.

3. Discussion

We have demonstrated that familiarity with the routine siren tests and test frequency and length of residency in Hawai‘i have not influenced greatly levels of understanding of the meaning of the siren. Awareness of the siren tests and frequency was high, but understanding of the precise purpose of the siren was uniformly low.

Despite the low level of understanding of the meaning of the siren, Raine (1995) reported that nearly everyone’s first and second responses to hearing the warning siren in 1994 were to turn on the radio (65%) or television (26%). However, most people did not even hear of the 1994 evacuation through the radio or television announcements, but rather second hand by telephone calls with family, friends and neighbors (Raine, 1995). By inference from Raine’s study, we suspect that many more than the 13% of our respondents that recorded an accurate meaning of the siren will actually turn on the radio or television during future siren soundings. However, public response to messages received from officials via television or radio will be moderated by messages from other sources.

The public responded in undesirable ways to the most recent tsunami warning in 1994. For example, Dudley and Lee (1998) reported that many people went to the ocean to watch the waves arrive when the tsunami warning was issued, which complicated official efforts to evacuate people to safer places inland from the coast. Also, several hundred incautious surfers went out to ride the tsunami waves (Dudley and Lee, 1998). However, no study has documented the source or content of the tsunami message(s) that these people received. We cannot presume that they responded only to the siren. Such behavior highlights the complexity in having the public respond to messages in ways that complement emergency response rather than hinder it.

Under the current siren system, the public needs to immediately seek out emergency information from radios or televisions once sirens are heard. However, as outlined above, warnings, particularly for infrequent events, can create a sense of ambiguity that results in delays as people look to others to clarify the situation and what they should do (Mileti and O'Brien, 1992). The complex nature of tsunami behavior, and the attendant difficulties in prescribing a course of action in response to specific signs of tsunamis, increases the likelihood of ambiguity during tsunami events.

The issues involved in warning of local tsunamis are complex and the current official warning system cannot ensure that the at-risk public will receive a timely warning of local tsunamis. Therefore, a new signal is needed that prompts people in hazardous areas

Tsunami Warnings: Understanding in Hawai‘i 10

to evacuate immediately, since the short-warning times effectively prohibit or severely limit opportunities for any search for information prior to action.

Natural warnings signs of tsunamis may provide the first and only alert of local tsunamis. However, natural signs are complex and descriptions of them are inconsistent, suggesting a need for additional research to better understand and describe their characteristics. In order for natural signs to serve as an alert, people must be familiar enough with the signs to evacuate dangerous areas immediately upon notice. This highlights another point― people must be able to recognize when they are in a safe place versus an unsafe place.

Earthquakes that produce either strong or mild ground-shaking in specific coastal areas both have produced destructive tsunamis (Dudley and Lee, 1998; Lander and Lockridge, 1989; Maramai and Tinti, 1997). Therefore, the severity of ground shaking should not be used as a determinant of behavioral response. The best rule of thumb is for people in coastal areas to evacuate and move to higher ground if any shaking is felt. This will inevitably result in the evacuation of some areas that are not subsequently impacted by tsunamis, so educational outreach must address this concern and how it may influence future behavior.

Some people in our surveys associated the siren with the hazard under investigation in each study. For example, most students in Maui that associated the siren with a hazard linked the siren with floods, and in O‘ahu, with storms. These associations are consistent with Mileti and O’Brien (1992, see their discussion of environmental information receiver characteristics). These researchers suggested that the characteristics of people who receive warnings that impact how they process risk information can be classified into three so-called “information receivers,” (environment, social and psychological attributes). The environment receiver includes physical and social cues, such as whether the survey was completed during a hazard event, or in the case of our surveys, which hazard was the focus of questioning. Our data suggest that students may be more affected by the environment receiver characteristic than are adults. This possibility should be considered in future outreach and surveys that involve multiple hazards in order to reduce biased results.

The high frequency and wide range of responses recorded in the ‘other’ category of Table 3 provide insight into the broad and flawed current interpretations of the siren. These responses may be associated with: 1) prior hazard experience where sirens were used (i.e., for tsunamis or hurricanes), 2) having obtained older information from a time when sirens had different hazard specific meanings, 3) having received inconsistent information from any source, or perhaps 4) the environment receiver of Mileti and O’Brien (1992).

4. Conclusions

High levels of awareness of the sirens and their tests and test frequency have not raised understanding of the warning system sirens above the low levels measured in the 1960s. Furthermore, the length of time people have lived in Hawai‘i has not positively influenced their awareness of the meaning of the siren. A clear need exists to raise awareness of the meaning of the siren and its implications for behavioral response throughout the state of Hawai‘i.

Tsunami Warnings: Understanding in Hawai‘i 11

The current single siren tone or Attention Alert Signal makes educational outreach easier than if there were multiple tones for specific hazards and behavioral response because the public is not required to learn and remember the differences in tones and response. However, consistent with other researchers (Sorensen, 2000), a single warning system does not serve the needs of all hazards. In Hawai‘i, the two distinctive threats posed by local and distant tsunamis require separate warning mechanisms. Hence, there needs to be a single warning signal for local tsunamis that alerts the at-risk people to evacuate to an area where they can learn more about the emergency situation at hand. In the absence of an effective official warning signal for local tsunamis, natural signs of tsunami may serve as a warning.

There is a need to improve public understanding of the siren and natural signs of tsunamis. There is also a need to improve scientific understanding of the physical characteristics of natural warning signs of tsunamis. This knowledge of natural signs of tsunamis should then be translated into more consistent and effective risk communication messages. This includes raising awareness of the natural signs of local tsunamis, a capability to recognize them, and their implications for behavioral response. This work should be viewed as complimentary to efforts that seek to improve understanding of the meaning of sirens because both levels of preparedness are needed for people to effectively respond to the threats posed by local and distant tsunamis.

Acknowledgements This study was funded by the Hawai‘i Sea Grant College Program. We thank the Hawai‘i Department of Education for supporting this tsunami warning research in Hawai‘i’s public schools.

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Table 1. Awareness that sirens are tested by subgroups Awareness of siren tests

Students (n)

(%)

Adults (n)

(%)

Total (n)

(%)

Yes 332 76.9 462 91.7 794 84.8 Don’t know 91 21.1 34 6.7 125 13.4 No 9 2.1 8 1.6 17 1.8 Total 432 100 504 100 936 100 χ2 = 42.046, df = 2, p = 0.000. Table 2. Awareness of the monthly siren test frequency by subgroups Awareness of the frequency of siren tests

Students (n)

(%)

Adults (n)

(%)

Total (n)

(%)

Once per month 288 66.7 433 85.9 721 77.0 Once per year 17 3.9 9 1.8 26 2.8 Don’t know 127 29.4 62 12.3 189 20.2 Total 432 100 504 100 936 100 χ2 = 48.727, df = 2, p = 0.000. Table 3. Understanding of the meaning of the siren by subgroups Interpretation of the meaning of the siren*

Students (n)

(%)

Adults (n)

(%)

Total (n)

(%)

Don’t know 301 69.7 254 50.4 555 59.3 Other (emergency, disaster, alert, tsunami, flood, etc)

207 47.9 243 48.2 450 48.1

Tune to radio/television 3 0.7 66 13.1 69 7.4 Total** 511 118.3 563 111.7 1074 114.8 *These are abbreviated write-in responses. **Percent does not total 100 because some respondents recorded multiple interpretations of the siren.

Tsunami Warnings: Understanding in Hawai‘i 13

Table 4. Understanding of the meaning of the siren by number of years respondents have lived in Hawai‘i Years lived in Hawai‘i Understanding of siren* 0-9 10-19 20-29 30-39 40-49 50-72 Total Don’t know or other** n 57 75 60 109 102 34 437 % 90.5 96.2 89.6 83.8 80.3 89.5 86.9 Tune to radio or television n 6 3 7 21 25 4 66 % 9.5 3.8 10.4 16.2 19.7 10.5 13.1 Total n 63 78 67 130 127 38 503 % 100 100 100 100 100 100 100 *These are abbreviated responses. **This category of response includes respondents that indicated they did not know the meaning of the siren or entered an inaccurate response. Table 5. Perceptions of what signs would alert respondent that a possible tsunami will occur by subgroups Expectations of future alerts of tsunami*

Student (n) (%)

Adult (n)

(%)

Total (n)

(%)

Official warning (siren, police)

59 76.6 55 62.5 114 69.1

Unusual sea-level changes 35 45.5 33 37.5 68 41.2 Earthquakes 18 23.4 45 51.1 63 38.2 Radio, television, news, media 26 33.8 28 31.8 54 32.7 Other geophysical event 4 5.2 8 9.1 12 7.3 Friends, family, neighbors, etc 1 1.3 3 3.4 4 2.4 Other 3 3.9 1 1.1 4 2.4 Did not respond 1 1.3 8 9.1 9 5.5 Total responses** 147 191 181 206 328 199 *These are abbreviated write-in responses. **Percent does not total 100 because some respondents recorded multiple responses. FIGURE CAPTION Figure 1. General distribution of electronic and mechanical sirens on four principal Hawaiian Islands. The ratio of km of coastline to number of sirens indicates that siren density is greatest on O‘ahu and lowest on Hawai‘i. Gaps along the coast typically reflect rural areas. Inset shows relative locations of islands. Siren data after Hawaii State Civil Defense (2004a).

Tsunami Warnings: Understanding in Hawai‘i 14

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