Twitter Under Crisis: Can we trust what we RT?
Marcelo Mendoza†

Barbara Poblete†

Carlos Castillo‡{mendozam,bpoblete,chato}@yahoo-inc.com†Yahoo! Research, Santiago, Chile‡Yahoo! Research, Barcelona, Spain

ABSTRACTIn this article we explore the behavior of Twitter users under an
emergency situation. In particular, we analyze the activity related to
the 2010 earthquake in Chile and characterize Twitter in the hours
and days following this disaster. Furthermore, we perform a preliminary study of certain social phenomenons, such as the dissemination of false rumors and confirmed news. We analyze how thisinformation propagated through the Twitter network, with the purpose of assessing the reliability of Twitter as an information source
under extreme circumstances. Our analysis shows that the propagation of tweets that correspond to rumors differs from tweets thatspread news because rumors tend to be questioned more than news
by the Twitter community. This result shows that it is posible todetect rumors by using aggregate analysis on tweets.

Categories and Subject Descriptors
H.3.3 [Information Storage and Retrieval]: Information Searchand Retrieval

General Terms
Experimentation, Measurement

Keywords
Rumor Identification, Social Media Analytics, Twitter

1.

INTRODUCTION

Twitter is a micro-blogging service that brings together millions
of users. Allowing its users to publish and exchange short messages, also known as tweets, through a wide variety of clients.
Users can post their tweets by sending e-mails, SMS text-messages,
directly from their smartphones and a wide array of Web-based services. Also, Twitter enables real-time propagation of information
to a large group of users. This makes it an ideal environment forthe dissemination of breaking-news directly from the news source
and/or geographical point of interest. Twitter has been found to

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1st Workshop on Social Media Analytics (SOMA ’10), July 25, 2010,
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Copyright 2010 ACM 978-1-4503-0217-3 ...$10.00.

be useful for emergency response and recovery e.g. [12]. Nevertheless, as we observe in this study, Twitter not only enables theeffective broadcasting of valid news, but also of baseless rumors.
In this paper we examine how Twitter is used during a particularemergency situation. Our main focus is to characterize Twitter as
an information source during this crisis. First, we present generalcharacteristics of the post-quake Chilean Twitter community, which
confirms some results observed in related work and extends existing research. Second, we focus on the issue of veracity. Based on
anecdotal evidence, we observed that false rumors spread quickly
contributing to general chaos in the absence of first-hand information from traditional sources. Motivated by this finding, our work
seeks to contribute towards a deeper understanding of valid news
and baseless rumors during a disaster. Additionally, we believethat some of our findings can be applied to some extent to othertypes of phenomenons, such as non-critical situations in which noa priori reliable information source is available.
The Chilean earthquake of 2010. The earthquake occurred off
the coast of the Maule region of Chile, on Saturday, February 27,
2010 at 06:34:14 UTC (03:34:14 local time). It reached a magnitude of 8.8 on the Richter scale and lasted for 90 seconds; it isconsidered the seventh stronger earthquake ever recorded in history1 . A few minutes after the earthquake, a tsunami hit the Chilean
shores. Nearly 500 people were reported dead after the disaster andmore than 2 million people were affected in some way.
In the hours and days after this earthquake, Twitter was used totweet time-critical information about tsunami alerts, missing people, deceased people, available services, interrupted services, roadconditions, functioning gas stations, among other emerging topics related to the catastrophe. The earthquake reached the levelof trending-topic in Twitter a few hours after the event. Figure 1
shows Twitter activity related to the hash-tag #terremotochile(chileearthquake) during a period of 10 days after the event 2 . Nevertheless, it should be noted that due to infrastructure issues, telecommunications (including Internet) were intermittent in Chile forthe first 48 hours after the quake. 3 The first tweets from Chile withinformation of the event were only observed around 3:56 AM (localtime). This meant that tweet frequency originated from Chile wasmuch lower than expected due to the circumstances.Therefore, during times when bursts of activity would have been expected (rightafter the quake), the number of tweets dropped considerably anddid not recover completely in the next 48 hours.
Research questions. To analyze the impact of Twitter on the prop1

http://en.wikipedia.org/wiki/List_of_earthquakes#
Largest_earthquakes_by_magnitude23

http://trendistic.com
http://www.nic.cl/anuncios/2010-03-01.html

Figure 1: #terremotochile trend activity during Feb. 27 and Mar. 8, 2010
agation of information during the Chilean earthquake, we perform
two types of studies over post-quake tweet data: (i) We characterize the usage and social networks of the days immediately after the
event. The goal of this task is to observe how rumors and news arepropagated and the dynamics of the followers/followees relationship. Also, we look at how the most authoritative users influence
topics discussed in the network and how terms in tweets are correlated, among other things. (ii) We investigate the ability of thesocial network to discriminate between false rumors and confirmed
news. To do this we examine tweets related to confirmed news andto rumors, classifying manually each tweet. The aim of this task
is to measure if and how the network filters false information fromaccurate news.
Our contributions. First, we characterized at a local level Twitter
data related to a recent natural disaster. Second, we study Twitteras an environment for the quick propagation of real and fictional
news and finally we discuss how users behave in when faced withthese types of information.
Roadmap. The remaining of the work is organized as follows:
Section 2 presents an exploratory analysis of the data, focused on
the presentation of the dataset and the description of the social interactions and keywords used during the quake. Section 4 presents
an analysis of confirmed news and false rumors obtained from ahuman-assessment process. In Section 5 we discuss related workand finally in Section 6 we show conclusions and future work.

2.

THE TWITTER NETWORK DURING AN
EMERGENCY

2.1

Experimental Framework

To study how Twitter was used during the earthquake in Chile,
we collected user activity data (tweets, plus other user-related information) during the time window between February 27, 2010 andMarch 2, 2010. To determine the set of tweets that were more orless local, or closely related to the Chilean Twitter community, weused a filter-based heuristic approach. This was necessary because
the data at our disposal from Twitter did not provide geographicalinformation about its users (there are no IP addresses or reliable location information in general). Therefore, we focused on the community that surrounded the topic of the earthquake. For this weselected all tweets using the Santiago timezone, plus tweets which
included a set of keywords (using background knowledge from theauthors) which characterized the event. These keywords included
hash-tags such as #terremotochile and the names of the affected geographic locations (all of them in Spanish). This prelimi-

Figure 2: Twitter activity (local time)nary selection indexed 4,727,524 tweets and 19.8% of these tweets
corresponded to replies to other tweets.
The activity for the entire collection is shown in Figure 2 andshows the highest volume on the last day (when communications
were restored in most of the country).

2.2

The Social Network

The indexed tweets are related to 716,344 different users, which
registered an average of 1,018 followers (number of people following that person) and 227 followees (number of people a person
follows). A scatter plot of number of followers versus number offollowees is shown in Figure 3.
The plot shown in Figure 3 is in a logarithmic format in bothaxes. The plot shows a great fraction of users registering less than
2,000 followees (friends). This phenomenon is due to the fact that
there is an upper limit on the number of people a user could follow. However, Twitter does not consider this constraint for users
who register more than 2,000 followers, being posible to follow thesame number of tweeters that registers as followers.
In the case of the followers count, this variable exhibits a considerable variance. It is common to observe that the number of followees is less than the number of followers. In fact, 355,343 users
registers more followers than followees (49.6%), 331,546 users
registers more followees than followers (46.2%) and only 29,455
users registers the same number of followers and followees (4.2%).
The number of authority users with more than 100,000 followers
is only 633 and in general they are mostly politicians/celebrities ormass media (e.g. CNN, The New York Times, Breaking News).

Figure 3: Followers/followees scatter plot.
Figure 4: Average number of tweets against number of followers/followees.

180000

Avg # of followers
Avg # of followees

160000
Avg # of followers / followees

We count the number of tweets each user contributed around theevent in Table 1. Over 50% of the users contributed only 1 tweet.
On the other hand, only 11.47% of users tweet 10 or more tweets
during this period. The average number of tweets per user (6.59) is
above the median, indicating that there are outliers who tweet far
more than expected.

140000120000100000

Table 1: Number of tweets per user.
# of tweets # of users Percentage
1
377,11252.64
2110,88715.48
351,6497.21
430,4784.25
520,6772.89
615,0062.09
711,406
1.59
8
9,342
1.30
9
7,642
1.07
10
82,145
11.47

Figure 5: Average number of followers/followees for the top
users.

We analyze the relation between the number of followers / followees and the number of tweets each user posts. In Figure 4
we plot the average number of tweets against the number of followers/followees.
As we can see in Figure 4, the average number of tweets pernumber of followers/followees exhibits a wide variance in the range[1, 104 ] which is also where the majority of the tweets are concentrated. The average number of tweets per number of followees isgreater than the average number of tweets per number of followers
in the range [1, 10], as opposed to the relation that exhibits the range[10, 104 ]. We can also see that the number of tweets increases when
the number of followers and followees increases. In fact, when thenumber of followers/followees is greater than 2,000 we can observethat the number of tweets increases by one order of magnitude.
To investigate how the authority of a user influences the numberof tweets that it produces, we retrieve users which register most
tweets. We calculate the average number of followers/followees
for the top-k users who register more activity during the event. We
plot the k variable in the range [50,500]. The results are shown in
Figure 5.
As Figure 5 shows, for the top users the number of followers is
by two orders of magnitude higher than the number of followees.

In fact, the number of followees reaches an average close to 1,800,
while the average number of followers is more than 100,000. We
can observe also that when the number of tweets decreases, thenumber of followers decreases. In fact, the top-50 most active users
register a significant fraction of the followers in the network.
In Table 2 we show the top-10 most active users during the earthquake, ordered by the number of tweets they post. Eight out ofthese ten users are associated to mass media outlets (either journalists of these organizations, or institutional accounts such as “CNNBreakingNews”). As we can see their number of followers is threeor four orders of magnitude larger than their number of followees.
We also investigated how these most active users relate to eachother. In Figure 6 (left) we show the followees graph for the top 20
most active users during the event. Each node represents a Twitteruser and each edge represents a relation is a follower of (friend).
The area of each node is proportional to the number of followers
each user registers. Figure 6 (left) shows that the social graph has
a strong connected component among these users. However, themost authoritative user (CNNBreakingNews, that appears on the
far left side of the graph) is followed by only two top users, andit does not register any is a follower of relationship in the top-20.

80000
60000
40000
20000
0
50

100

150

200 250 300 350
Number of top users

400

450

500

Figure 6: Followee relationships for top-20 most active users, node size represents the # of followers each user has (left), or # of tweets
posted by the user (right).

Table 2: Top-10 most active users during the quake. Users related to mass media sources (mostly news) are in boldface.
User
tweets followers friends
BreakingNews
8584
1665399
203
CruzRojaChilena
7940
6101
978
NicolasCopano
7004
41324
0
MauricioBustamante 5579
47846
323
Cooperativa.cl
5526
19199
0
24HUltimaHora
4877
9132
50
CNNBreakingNews
4767
2930769
28
Tele13
4438
32778
29061
SocialNetworksCafe
4385
2977
0
FernandoPaulsen
4112
35733
107

Table 3: Top-10 trends registered in our dataset (ordered bynumber of tweets).
hash-tag# of tweets # of users#terremotochile
9,810
4,122
#chile4,246
2,562#tsunami
1,393
1,010
#fuerzachile
944
641#hitsunami
800
613#terremotochile:
791
212#prayforchile
680
595#terremoto
670
387#terremotoenchile
523
346#prayersforchile465
446

In the social graph of our entire collection this authority follows
28 users but it is followed by 2,930,769. 11 of the 20 most active
users correspond to mass media organizations or celebrities related
to mass media. The rest of the top-20 belong to other types oforganizations, such as non-profits, and the also register few friends(users that they follow or followees).
We also illustrate the activity of each of the top-20 users during
the quake. In Figure 6 (right) shows the same relationship as Figure 6 (left) but in this case the size of each node represents thenumber of tweets of the user. As Figure 6 (right) shows, followees
relationships are closely related to the number of tweets each user
posted during the event. Users with most activity are more connected among each other. In particular, the most connected component of the followees graph represents the Chilean news media
that is strongly influenced by the event. It is not the case of themost authoritative users, like CNN, which are located on the border of the graph because they register activity also in other topics.
Thus, observing only activity related to the earthquake, the connected component of news media concentrates a significant fractionof the tweets during the event.
The most active trending-topics related to the earthquake areshown in Table 3. This table also shows the number of tweets eachtrend registers and the number of users who contributed at least one
tweet to the trend. As Table 3 shows, the most popular trendingtopic is identified with the #terremotochile hash-tag. It registers
close to 10,000 tweets during the event, posted by more than 4,000
users. All topics are about the Chilean earthquake. However, thefraction of users who contributed to a trending-topic is not very significant compared to the total number of users who posted tweets
during the event. In fact, the total number of tweets registered forthe top-10 trending-topics is only 20,322, which represents 35.52%of the tweets posted by the top-10 most active users.
The analysis of the Twitter network during this crisis exhibits
similar results as prior work (see for example Kwak et al. [5],where Twitter is not analyzed under emergencies/atypical situations). Therefore the characteristics of the network maintain theirproperties in atypical situations. This is a static observations because in this first approach, we did not measure how the network
evolved during the days of the earthquake.

3.

TWITTER ACTIVITY DURING AN
EMERGENCY: THE EARTHQUAKEIn this section, we first analyze Twitter activity in our post-quake
dataset. Then, we examine the nature of the information disseminated through Twitter during this critical event.
We analyze the variations in activity during the first day after
the earthquake. Figure 7 shows the number of tweets registered
for this day which contained the word “earthquake” (“terremoto”
in Spanish). The impact of the event was very high the first day,measured in the number of tweets shown in Figure 7. Tweets containing the term “earthquake” register two peaks in activity, the firstone a few moments after the quake, and the second one at 1:00 p.m.
(local time). It should be noted that a large portion of tweets wereaffected by Internet interruptions during this day.
As mentioned before, the impact of the quake also affects trendingtopics. Figure 8 shows Twitter activity for two trending-topics. The
first one, identified with the “Viña del Mar Festival” label corresponds to a local music festival that normally gathers the attentionof most local media during the studied time window. The second

works over the Twitter social network we plot the graphs considering intervals of 15 minutes.
Figure 9 shows that tweets with the term “earthquake” are quickly
propagated through the social network. In fact, we observe that
only thirty minutes after the quake some re-tweet graphs exhibit interesting patterns. In some cases tweet propagation takes the formof a tree. This is the case of direct quoting of information. And inother cases the propagation graph presents cycles, which indicatesthat the information is being commented and replied, as it is passed
on. This last case involves reciprocity in the information dissemination process. The biggest subgraph is shown in Figure 9(d) andit displays 6 degrees of separation. The remaining subgraphs haveless than 6 degrees of separation. Finally we can observe that asignificant fraction of the subgraphs has only one or two edges.
Figure 7: Frequency of tweets containing the term “earthquake” (Feb. 27, local time).

Figure 8: Two trending-topics with different fates during theearthquake.

trending-topic, identified with the “Chilean earthquake” label, corresponds to the emerging earthquake trend hash-tag.
As Figure 8 shows, the “Viña del Mar Festival” trend decays
quickly just a few moments after the quake. Moreover, the activityof this topic is reduced to zero just twenty minutes after the quake.
On the other hand, the “Chilean earthquake” trend increases significantly in the first two hours after the quake. These results suggest,
as we can expect, that the Twitter activity is proportional to thesignificance of the event.
We illustrate the impact of the quake by measuring the re-tweet
activity during the first hours. A re-tweet (RT) is a quote of another tweet, which may or may not include a comment or reply.
However, most re-tweets posted by a user are of tweets originallyposted by one of its followees (which can also be re-tweets). Therefore, re-tweet activity reflects how the social network helps in the
propagation of the information. An active social network facilitates
the quick dissemination of relevant tweets. In certain way, when auser reads a tweet and re-tweets this to other users, it determines
the importance of the original tweet. As a collective phenomenon,
how deep re-tweets cover the social graph indicates the relevanceof the tweet for the community.
In Figure 9 we show the re-tweet graphs that emerge in the firsthour post-quake. In order to illustrate how the propagation process

Tweet vocabulary. We analyze the vocabulary of tweets in this crisis situation. Intuitively, we expect a significant amount of tweets tocontain terms related to the earthquake. Therefore, we also expect
a high correlation of terms used in the collection.
To illustrate the properties of the Twitter vocabulary during theChilean earthquake, we retrieve the top-50 most used terms eachday. Then we count the number of occurrences of these terms in
tweets. In this analysis, the vocabulary of terms has been processed
to eliminate accents, digits and punctuation. Moreover, stopwords
found in the collection have also been eliminated.
We plot term collections as term clouds. The size of each term is
proportional to the number of occurrences each term registers in ourdataset. The terms have been translated from Spanish to English.
Term clouds are plotted in Figure 10.
Figure 10(a) shows the term cloud for the first day of the event.
As the term cloud shows, the most significant terms are “tsunami”
and “deceased”. Thus, these terms illustrate the focus of tweets forthe first day: the tsunami which hit the shores of Chile minutes after the quake, and the death toll count. In Figure 10(b) we show
the term cloud for the second day of the catastrophe. In this day
topics are focused on “missing people”, as a consequence of theearthquake and the tsunami of the previous day. Terms as “list” or“favor” indicate that tweets are focused on asking for help to locate
missing people. In Figure 10(c) we show the term cloud for thethird day of the event. As in the previous day, people are looking
for help to locate missing people. Popular terms are “help”, “people”, “favor” and “people finder”. Another term used this day was“Concepcion”, the name of a city located very close to the epicenter of the quake. Finally, Figure 10(d) shows the term cloud forthe fourth day of the event. Some terms are related to the need offinding people, such as “help”. But another trending-topic emerges
this day. A NASA report released this day claims that in addition to causing widespread death and destruction, the earthquake
may have shifted the Earth’s axis permanently and created shorter
days4 . Thus, tweets where terms as “Earth” and “axis” became very
popular after the fourth day.

4.

FALSE RUMOR PROPAGATIONIn this section we conduct a case study to test the veracity of information on Twitter and how this information is spread throughthe social network. To achieve this task, we manually selected
some relevant cases of valid news items, which were confirmed
at some point by reliable sources. We refer to these cases as confirmed truths. Additionally, we manually selected important casesof baseless rumors which emerged during the crisis (confirmed to
be false at some point). We refer to these cases as false rumors. Our
4
Based on calculations thus far, every day should be 1.26 microseconds
shorter(a) 03:35:00 - 03:49:00(b) 03:50:00 - 04:04:00(c) 04:05:00 - 04:19:00(d) 04:20:00 - 04:34:00

Figure 9: Trend propagation: tweets and re-tweets that include the term “earthquake” in the first hour post-quake. Gray edges
indicate past re-tweets.
goal is to observe if users interact in a different manner when facedwith these types of information. Each case studied was selectedaccording to the following criteria:
1. A significant volume of tweets is related to the case (close to
1, 000 or more).
2. Reliable sources (external to Twitter) allow to asses if theclaim is true or false.
The following step was to create a list of 7 confirmed truths and7 false rumors. This list was obtained by manually analyzing samples of tweets and also using first-hand background knowledge ofthe crisis. For example, a true news item (confirmed truth) was
the occurrence of a tsunami in the locations of Iloca and Duao. In
fact this information was quickly informed through Twitter sources
while government authorities ignored its existence. On the other
hand, a baseless rumor was the death of locally famous artist Ricardo Arjona. In each case we collected between 42 and 700 unique
tweets for classification (identical re-tweets were discarded for classification purposes). These tweets were retrieved by querying thecollection using keywords related to each true or false case. The
next step was to classify tweets into the following categories: affirms (propagates information confirming the item), denies (refutes
the information item), questions (asks about the information item),and unrelated or unknown. We automatically propagated labels insuch a way that all identical re-tweets of a tweet get the same label.
The results of the classification are shown in Table 4.
The classification results (see Table 4) shows that a large percentage (95.5% approx.) of tweets related to confirmed truths validate the information (“affirms” category label). The percentage oftweets that deny these true cases is very low, only 0.3%. On theother hand, we observe that the number of tweets that deny information becomes much larger when the information corresponds toa false rumor. In fact, this category concentrates around 50% of
tweets. There are also more tweets in the “questions” category inthe case of false rumors. This information is shown in Figure 11.
These results show that the propagation of tweets that correspondto rumors differs from tweets that spread news because rumors tend
to be questioned more than news by the Twitter community. Notice that this fact suggests that the Twitter community works like acollaborative filter of information. This result suggests also a very
promising research line: it could posible to detect rumors by using
aggregate analysis on tweets.

5.

RELATED WORKTwitter has attracted a considerable amount of research in recent
years. For the interested reader, reference [8] presents a general
overview of some key Twitter characteristics including the distribution of different types of tweets. A more recent and in-depth
analysis is due to Kwak et al. [5]. An application of twitter to de-(a) 27 Feb(b) 28 Feb(c) 01 Mar(d) 02 Mar

Figure 10: Term clouds for the first days after the Chilean earthquake.

Case

Table 4: Classification results for cases studied of confirmed truths and false rumors.
# of unique% of# of unique # of unique
tweetsre-tweets“affirms”“denies”

Confirmed truths
The international airport of Santiago is closed
The Viña del Mar International Song Festival is canceled
Fire in the Chemistry Faculty at the University of Concepción
Navy acknowledges mistake informing about tsunami warning
Small aircraft with six people crashes near Concepción
Looting of supermarket in Concepción
Tsunami in Iloca and Duao towns
TOTAL
AVERAGE
False rumors
Death of artist Ricardo Arjona
Tsunami warning in Valparaiso
Large water tower broken in Rancagua
Cousin of football player Gary Medel is a victim
Looting in some districts in Santiago“Huascar” vessel missing in Talcahuano
Villarrica volcano has become active
TOTAL
AVERAGEtect news events is due to Sankaranarayanan et al. [10].
Twitter in emergency events According to the widely used taxonomy of Powell and Rayner [9] (cited e.g. in [6, 7]) there are several
stages in a disaster: 1) warning, 2) threat, 3) impact, 4) inventory, 5)# of unique“questions”

301
261
42
135
129
160
153
1181
168,71

81
57
49
30
82
44
32

291
256
38
124
125
149
140
1123
160,43

0
0
0
4
0
0
0
4
0,57

7
3
4
6
4
2
4
30
4,29

50
700
126
94
250
234
228
1682
240,29

37
4
43
4
37
36
21

24
45
62
44
218
54
55
502
71,71

12
605
38
34
2
66
79
836
119,43

8
27
20
2
20
63
76
216
30,86

rescue, 6) remedy, and 7) recovery. Most studies of microblogging
during emergencies, including this one, focus on the stages 3 to 5
according to this taxonomy. These are the stages at which more traditional communication channels are less effective than emerging

6.

Figure 11: Classification of tweets belonging to “confirmed
truths” and “false rumors”.

ones.
Some of the first accounts of the use of Twitter during emergency events appeared in Wired on October 20075 in relation to thewildfires in Southern California. Journalists hailed the immediacyof the service which allowed to report breaking news quickly – inmany cases, more frequently than most mainstream media outlets.
Kireyev et al. [4] studied Twitter during two earthquakes in American Samoa and Sumatra that overlapped in time (both on September 30th 2009), with an emphasis on studying how to use topic
modeling on the content of the tweets. Earle et al.[2] from the US
Geological Survey reported they started to correlate tweets withseismic data to improve emergency response in late 20096 . In
early 2010 researcher Markus Strohmaier coined the term “Twicalli
scale” as a description of Twitter’s response to recent earthquakes
in California and Haiti7 .
Hughes and Palen have described the use of Twitter during emergencies such as hurricanes and mass convergence events such aspolitical-party conventions [3]. Among other findings, they observe that the fraction of reply –prefixed by “@”– tweets is lower
during these events (6-8% vs. 22% normally); that the percentageof tweets that include a URL is higher (40-50% vs. 25% normally);
and that users that start using twitter during an event tend to adopt
twitter afterwards.
Longueville et al. [1] describe the use of Twitter during a forest
fire close to Marseille in mid-2009, they identified different typesof twitter users: those related to mass media outlets, those acting
as aggregators of information, and normal citizens. Sarah Vieweg
and collaborators have studied extensively the use of Twitter forsituational awareness during emergency situations such as floods
and grassfires; see [12, 13, 11] and references therein.
In the specific case of the Chilean earthquake of 2010 discussed
in this study, bloggers have published first-hand accounts on how
they used twitter during the emergency8 .
5http://www.wired.com/threatlevel/2007/10/
firsthand-repor/
http://www.wired.com/threatlevel/2007/
10/in-disasters-ev/
6

http://www.wired.com/wiredscience/2009/12/
twitter-earthquake-alerts/
7
http://mstrohm.wordpress.com/2010/01/15/
measuring-earthquakes-on-twitter-the-twicalli-scale/8

http://portalcesfam.com/index.php?

CONCLUSIONSIn this paper we presented a study of Twitter during an emergency situation: the recent 2010 earthquake in Chile. First, we analyzed and characterized the social network of the community surrounding the topic. This analysis confirmed that network topology
characteristics remained unchanged regarding studies performed
under normal circumstances (see for example the recent paper ofKwak et al. [5]). On the other hand we show new interesting insights on how trending-topics behave in this situation and how they
propagate. Therefore, our findings on a more or less local network
present no loss of generality for larger communities. Another interesting insight is that the vocabulary used in crisis situations exhibitsa low variance. This fact indicates that tweets tend to describe acommon/global topic, diminishing the network entropy.
Second, we focused on the propagation of confirmed truths andfalse rumors on Twitter. Our results, on a small set of cases, indicate that false rumors tend to be questioned much more than confirmed truths, which we consider a very positive result. As an application, given that detecting when a tweet is asking for information
should be possible to do with state-of-the-art text classifiers, microblogging platforms could for instance warn people that manyother users are questioning the information item they are reading.
This would provide signals for users to determine how much totrust a certain piece of information.

7.

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