Availability of a particular device does not necessarily mean that the household or respondent will actually receive a warning through these devices in case a tsunami really strikes. Generally, the local actors perceive the use of private devices as doubtful due to the possibility of a break‐down of the electricity supply (non‐battery operated television and radio) or the interruption of communication transmission of mobile phones following a strong earthquake. As to landline phones, the public can only receive the warning indirectly through social networks as long as the transmission line is not damaged. However, these private devices are still considered useful due to the absence of public dissemination devices that cover the whole city of Padang (or the potentially affected city areas) and
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it is commonly accepted that redundancy of various dissemination devices is important to guarantee quick distribution of the warning message to all potentially affected people.
As described in the previous discussion on public devices availability, the promotion of community‐
based efforts in some pilot mosques and Kelurahan has been taking place. However, during the time of data collection, these public devices had not been (fully) utilized yet, so it was not possible to assess their effectiveness based on any quantitative data yet. Thus, the analysis below can only show the effectiveness of private devices.
Based on the UNU‐EHS Household Survey 2008, 73.5% of the respondents had received a tsunami warning during the earthquake event in September 2007. Most of them had received the information through one or more devices. However, not all available devices were utilized to disseminate or receive the warning information. Indeed, the analysis of the survey revealed that the receipt of the warning through particular devices was much lower than the availability of the devices itself. The dissemination rate of various private devices was calculated as the proportion of people having the devices effectively receiving information through them (Table 5‐5). As seen in Table 5‐5, the effectiveness or dissemination rate of radio and television is less than half than its availability, while the effectiveness of mobile phones is even lower than 10 times of its availability. The utilization of the devices also differs by gender and age groups. The survey showed that more female respondents received the information from television (Cramer‐V coefficient 0.107, significant at p<0.01). In contrast, the dissemination rate via mobile phones (SMS) was less for female respondents (Cramer‐V coefficient ‐0.091, significant at p<0.05) and respondents older than 50 years (Cramer‐V coefficient ‐ 0.113, significant at p<0.01).
Table 5-5 Dissemination rate of the warning information through private devices in September 2007
Devices Dissemination rate (%)
Radio 45.3%
Television 42.2%
Mobile phone (SMS) 8.8%
Source: Own analysis based on the UNU‐EHS Household Survey 2008
Additionally, it should be taken into consideration that aside from the fact that the majority of the people have access to particular devices, friends and neighbours play a big role in disseminating the warning. The survey showed that of the 67.1% of the respondents who received the warning, had also been informed about the warning by friends and neighbours.
The earthquake event in September 2009 also occurred at the same daytime (afternoon) as the event in 2007 and both events were quite comparable. Based on a household survey conducted by GTZ in 2009, 84% of the respondents had received information about the earthquake and potential tsunami. However, only 20% of the respondents received information within 30 minutes after the earthquake event. For this event, dissemination rates of the warning through various private devices
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were also calculated (Table 5‐6). Here, mobile phone and television had an even much lower rate due to a breakdown of the electricity supply and mobile phone transmission during the event.
Table 5-6 Dissemination rate of the warning information through private devices in September 2009
Devices Dissemination rate (%)
Radio 39.1%
Television 4.8%
Mobile phones 0.8%
Landline phones
8.6%
Source: Own analysis based on GTZ Household Survey 2009
In both events, the radio was identified as the most effective dissemination device. This has been also confirmed by the local actors, who stated that (battery‐operated) radio, and additionally handy‐
talky communication at the community level had proven to be the best dissemination devices (FGD with local actors Bonn, June 21‐25, 2010). The dissemination of earthquake and potential tsunami information through mobile phones (SMS) is also being improved and extended to cover more people in the future. Traditional devices such as Kentongan (made of bamboos) is also locally used, however, there are no further indications yet on the effectiveness and utilization of this device.
Moreover, the content and clearness of the warning message vary by device. The UNU‐EHS Household Survey 2008 shows that 51.3% of the respondents could be reached by television and radio, which was primarily used to disseminate direct information from the Tsunami Warning Centre and local government, and 22.2% could be reached only indirectly via other channels such as mobile phones, friends and neighbours. It was found that more people who had received the warning directly could understand the message without difficulties. Such difficulties may cause wrong interpretations of the message and lead to unexpected behaviour during evacuation.
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Figure 5-13 Understanding the warning by dissemination devices
Source: Own analysis based on the UNU‐EHS Household Survey 2008
Confirming the results of the quantitative analysis, the coverage of existing public devices was still perceived by the people as insufficient. For instance, some households interviewed mentioned that the sound of the siren was not clearly heard. Also, the community response groups at the local level who had been trained to help people in the neighbourhoods to evacuate, had been overwhelmed by the number of exposed people they had to support that vastly exceeded their capacity.