Is a subject singular or plural with a modifying prepositional phrase that has plural objects?
Would it be "has" or "have" in this case:
The earthquake, along with its subsequent aftershocks, has/have created an atmosphere of panic among the city's residents.
The subject is "earthquake." That is the entire subject. As such, the sentence would be written:
The earthquake, along with its subsequent aftershocks, has created an atmosphere of panic among the city's residents.
"Along with its subsequent aftershocks" is a prepositional phrase. A prepositional phrase is never part of a subject. It does not affect the count of the subject. Whatever is said in a prepositional phrase, no matter how plural it may be, does not make a singular subject plural.
The only thing that can make an otherwise singular subject plural is the conjunction "and." If the word "and" were used instead of "along with," then the verb would be "have."
Here is a link that explains all of this in more detail:
The Subject of the sentence is the noun phrase The earthquake. The preposition phrase along with its aftershocks is not integrated into the Subject. It is parenthetical. We can show this because we can move this phrase around:
The verb, of course, agrees with the head noun in the Subject noun phrase. This is the singular noun earthquake. For this reason we need singular verb agreement here:
The earthquake, along with its subsequent aftershocks, has created an atmosphere of panic among the city's residents.
(However, there is much more to this story than meets the eye!)
This is a very, very good question. The expression along with is used to indicate addition and inclusion. It happens to form a prepositional phrase along with the following item, often a noun phrase.
Along with seems very similar, therefore, to other expressions such as as well as. The item as well as is also used to express addition and inclusion. The last word in as well as is also a preposition and can form a preposition phrase with a following noun phrase.
Both of these items form phrases that can function as Adjuncts (read adverbials):
Below we see them in relation to Subjects:
These phrases are clearly Adjuncts in each pair of sentences. There is some interesting data here that will be important later. You'll notice that in the first sentences the as well as/along with phrases occur before other noun phrases, not after them. Secondly, in both pairs of sentences, notice that these phrases are not integrated with the other noun phrases. We can move the adjuncts about:
Lastly notice that in the second pair of sentences further above that even when these adjuncts come directly between the Subject and the verb, we do not count them as part of the Subject, the verb agrees with the Subject alone. We do not see the plural verb agreement that we would see if we used a coordinator (read 'coordinating conjunction') such as and:
In the case above both beauty and love are part of the Subject, which is what causes the plural verb agreement.
So why is this a good question then if both along with and as well as both head phrases which function as Adjuncts in the clause? Surely this is a cut-and-dried issue?
It most certainly is not!
Coordination
Consider the following sentence:
As the examples above show the additive expression as well as can also be a coordinator. In the sentences above the verb is showing plural agreement because both noun phrases are counted together as part of the Subject. The Subject in the first example is He as well as they. Here as well as is behaving like the coordinator and:
Notice that the sentence doesn't sound very good if we try to use as well as as an adjunct here:
Also notice that we cannot move about the second coordinates here. The term as well as must also come between the two noun phrases. These are not Adjuncts:
Both the Cambridge Grammar of the English Usage (p. 1316-7) and Merriam-Webster's Concise Dictionary of English Usage, (p.101-2) talk in some depth about the additive expression as well as being a coordinator. If you're interested you can read some of the CaGEL entry underneath this post.
It would be reasonable therefore to think that perhaps along with can also be a coordinator. If this were the case, we should be able to use plural verb agreement with a coordination using along with.
The Original Poster's question
So, the Original Poster has good reason to wonder whether we can use a plural verb with their example sentence. Clearly if we used the expression as well as this would be viable:
We could also use as well as as an adjunct here:
In the first sentence the Subject is the earthquake, as well as its subsequent aftershocks. The two coordinated noun phrases inside the Subject, the earthquake and its aftershock, make the Subject plural, causing plural verb agreement.
In the second sentence, the Subject is The earthquake. Because as well as is not a coordinator here the phrase as well as the aftershocks is parenthetical, occurring outside the Subject noun phrase.
So what about along with? Well we can definitely use along with to form a preposition phrase adjunct. We saw that earlier above:
Let's try a plural verb form and see if we can force along with into being a coordinator:
The result here is not very good. There were good reasons to think it might be possible but it doesn't seem to be the case.
Notice that we seem to be able to move the along with phrase around here showing clearly that it is an Adjunct:
The along with phrase here is definitely not part of the Subject so it seems that our doubts were unfounded.
Conclusion
"What?", I can hear you say. "After all that, along with can't be used as a coordinator. It heads adjuncts that aren't integrated into the Subject. It can't turn a singular noun phrase into a plural one by introducing an extra noun phrase. Why didn't you say that at the beginning? We could have saved a lot of time and energy. Good grief, this isn't such an interesting question at all."
Oh ye of little faith! Have a look at this interesting example down here:
In this example from CaGEL (p.1316) we see both occurring with along with in a correlative coordination. So, it seems that at the margins along with can perhaps be regarded as a coordinator. In the sentence above along with the new testament is not an Adjunct. It cannot be moved, and furthermore is positively required because of the presence of both. Could we use a correlative construction like this as a Subject? I'm not sure. Let's try:
This sentence seems marginally alright to me. I suspect there are other more convincing examples out there. One thing is for sure, which is that along with certainly does occasionally occur in correlative constructions such as the one from CaGEL.
It seems then that in normal sentences along with heads prepositional phrases which function as adjuncts. These would not normally affect verb agreement in a sentence such as the Original Poster's where they wouldn't have the status of a coordinate in the Subject noun phrase. This contrasts the behaviour of along with with the behaviour of items such as as well as. However, along with appears to have hidden coordinator potential; it can occasionally enter into correlative constructions with the word both. It is conceivable therefore, that there may be examples in the literature of such correlative constructions occurring as Subjects in finite clauses. In such instances we would expect plural verb forms. Along with appears to have hidden talents.
References:
Some examples here were taken from:
- The Cambridge Grammar of the English Language, Huddleston & Pullum, 2002
Others were taken from:
- Merriam-Webster's Concise Dictionary of English Usage
The decision to write
The earthquake, along with its subsequent aftershocks, has created an atmosphere of panic among the city's residents.
instead of the simpler
The earthquake and its subsequent aftershocks have created an atmosphere of panic among the city's residents.
reflects a choice by the author to stress the idea that that the earthquake alone sufficed to create an atmosphere of panic in the populace. By putting the aftershocks into what amounts to a parenthetical phrase, the author emphasizes the original earthquake as the main factor in the terrorizing of the citizenry, with (oh yes) the aftershocks as relevant factors, too.
If you interpret "along with" as being nothing more than a fancy way of saying "and," you give yourself grounds for using have instead of has—but you also call into question the author's judgment in using that more convoluted wording and especially in setting off the "along with its subsequent aftershocks" phrase with commas.
The converse problem would arise if the author had written the sentence this way:
The earthquake—and its subsequent aftershocks—has/have created an atmosphere of panic among the city's residents.
If the aftershocks weren't an afterthought, the author would have done better to dispense with the em-dashes and to treat the earthquake and the aftershocks as a joint subject responsible in combination for the atmosphere of panic. But by breaking out the "and its subsequent aftershocks" phrase, it seems to me, the author assigns primary credit to the earthquake and only secondary or tertiary credit to the aftershocks. Though I wouldn't want to change have to has in that case (if the rest of the wording and punctuation remained unchanged), I would want to change and to along with or as well as or reinforced by or followed by, and then choose has over have.
So far, I've been discussing the written form of the example sentences. In spoken English, the punctuation disappears and you have to gauge the appropriate form of the verb by the pauses, changes in intonation, or other signals accompanying the statement (thanks to Araucaria for pointing out that intonation is a crucial factor; for a discussion of intonation contours, Araucaria recommends Sandra Döring, "Quieter, faster, lower, and set off by pauses?," in Nicole Dehé & Yordanka Kavalova, eds, Parentheticals [2007]). But if I were hearing the OP's example read aloud, I would take "along with" to signal a parenthetical break from the main subject and its associated verb, and I would expect the primary subject "earthquake" to take a singular verb.
